Ergänzende Informationen zu Publikationen von Bruno Baur

Bitte kontaktieren Sie Bruno Baur um Kopien dieser Publikationen zu erhalten

2023  Genetic Diversity and Population Structure Derived from Body Remains of the Endangered Flightless Longhorn Beetle Iberodorcadion fuliginator in Grassland Fragments in Central Europe — Rusterholz H-P, Ursenbacher S, Weibel U, Coray A & Baur B — Diversity 15: 16   doi> 10.3390/d15010016 

Knowledge of patterns of genetic diversity in populations of threatened species is vital for their effective conservation. However, destructive sampling should be avoided in threatened species so as not to additionally increase the risk of local population extinction. We exclusively used beetle remains and beetles collected after death to analyze local and regional patterns of genetic variation in the endangered flightless longhorn beetle Iberodorcadion fuliginator in the border region of Switzerland, France and Germany, in grassland remnants. We extracted DNA from the beetles’ remains and genotyped 243 individuals at 6 microsatellite loci. We found moderate genetic differentiation between populations, each belonging to one of two metapopulations situated on either side of the river Rhine, but distinct genetic differentiation between populations across metapopulation. The genetic distance between populations was correlated with the geographic distance between the sites sampled. Genetic structure analysis inferred the presence of two genetic clusters. The populations in the Alsace (France) represent one cluster, together with the Swiss populations near Basel, which is separated by the river Rhine from the cluster composed of the populations in southwestern Germany. Thus, the historical separation by the river Rhine surpasses more recent effects of human induced habitat fragmentation on the genetic differentiation in I. fuliginator.

Keywords: agricultural intensification - Cerambicidae - habitat degradation - habitat fragmentation - insect decline - microsatellites - natural barrier - non-invasive method - semi-natural grassland - species conservation

2022  Millipedes step up: species extend their upper elevational limit in the Alps in response to climate warming — Gilgado JD, Rusterholz H-P & Baur B — Insect Conservation and Diversity 15: 61–72   doi> 10.1111/icad.12535 

1. Climate warming is predicted to result in changes to phenology, behaviour and abundance as well as poleward shifts or upslope displacements of the distribution of species. However, climate-warming induced changes in distribution patterns have rarely been studied in ground-dwelling arthropods.
2. We investigated changes in the upper elevational limit and relative abundance of 11 millipede species by repeating historical surveys from 1917 to 1919 in five valleys in the Swiss National Park (Eastern Alps) in 2018-2019.
3. We found that the upper elevational limit for 10 out of 11 millipede species has risen, on average, by 161 m in 100 years, accompanying a 1.5 C rise in mean annual temperature in the investigation area. The 10 millipede species differed in upslope expansion of their distribution with the shift ranging from 50 m to 363 m.
4. The relative abundances of species (percentage of individuals sampled for each of the 11 millipede species) were very similar in 1917-1919 and 2018-2019. Only three species showed a change in frequency >6% over 100 years: two species had reduced abundances by 13.7% and 12.5% in the recent survey, while one species increased in abundance by 12.2%.
5. We provide evidence showing that soil-dwelling millipede species with low dispersal ability have raised their upper distribution limit to higher elevation between the surveys done in 1917-1919 and 2018-2019. This upslope shift in distribution is most probably due to the significant increase in temperature recorded in the investigation area in past decades.

Keywords: Alps - Diplopoda - global warming - ground-dwelling invertebrates - historical data - mountain species - Myriapoda - range shift - Swiss National Park

2022  New measures for quantifying directional changes in presence-absence community data — Schmera D, Legendre P, Eros T, Toth M, Magyari EK, Baur B & Podani J — Ecological Indicators 136: 108618   doi> 10.1016/j.ecolind.2022.108618 

Variation in community composition and species turnover are different types of beta diversity, expressing nondirectional and directional changes, respectively. While directional changes (e.g. turnover) along geographic gradients can be studied in any direction depending on the hypothesis of interest to researchers, temporal changes can only be meaningfully studied from past to present. Although a wide variety of methods exist for partitioning variation and related community-level phenomena such as similarity, richness difference and nestedness, approaches evaluating species turnover along geographic or temporal gradients, based on an analogous conceptual framework, are rare. We therefore look into the possibilities for examining different aspects of directional changes along a gradient when presence-absence community data are available. Measures of community overlap, as well as species loss and gain from one sampling unit to another along a gradient are combined to define a variety of turnover and nestedness concepts and to derive functions for their quantification. Each concept represents an ecological phenomenon to be indicated (indicandum), whereas measures (indicators) quantify relevant properties of these concepts. The measures use the raw number of species as well as relativized forms in accordance with the well-known Jaccard and Sorensen indices. The main innovation is the development of new measures of directional community change. We demonstrate differences between traditional nondirectional and the new directional measures and use several examples to show that actual communities display directional responses to a particular ecological gradient. The new measures therefore reveal an uncovered aspect of community ecology.

Keywords: components of beta diversity - directional community indices - gradient analysis - nestedness - presence-absence data - turnover

2022  Subtle Effects of Experimental Grassland Fragmentation on Density, Species Composition and Functional Dispersion of Gastropods — Braschler B, Oggier P & Baur B — Diversity 14: 474   doi> 10.3390/d14060474 

The fragmentation of continuous habitats has significant consequences for species and for the functional diversity of plant and animal communities. Fragmentation effects can be indirect, can occur at different spatial scales and may vary over years. Small fragmentation-related effects may only be detected in standardized, controlled field experiments accounting for the natural variation in environmental conditions and in remnants of habitat. Using a non-invasive trapping approach, we examined the responses of terrestrial gastropods (snails and slugs) to small-scale habitat fragmentation in a controlled experiment conducted in three species-rich, nutrient-poor calcareous grasslands in the Jura Mountains, Switzerland, over four years. We found site-specific differences in species richness, individual density, and species composition. Experimental grassland fragmentation did not significantly affect species richness or density, but affected functional dispersion (a measure of functional diversity) in the final year, indicating that fragmentation-related changes may occur with a time delay. Similarly, experimental fragmentation influenced the mean shell size of the snail assemblage and the proportions of individuals with certain life-history traits or habitat preferences in some years. The observed fragmentation effects were subtle and varied over time, underlining the importance of controlled field experiments.

Keywords: biodiversity - body size - functional diversity - habitat fragmentation - habitat preference - invertebrates - slugs - snails - species composition - terrestrial gastropods

2022  Six groups of ground-dwelling arthropods show different diversity responses along elevational gradients in the Swiss Alps — Gilgado JD, Rusterholz H-P, Braschler B, Zimmermann S, Chittaro Y & Baur B — PLOS ONE 17: e0271831   doi> 10.1371/journal. pone.0271831 

Elevational gradients along mountain slopes offer opportunities to study key factors shaping species diversity patterns. Several environmental factors change over short distances along the elevational gradient in predictable ways. However, different taxa respond to these fac- tors differently resulting in various proposed models for biodiversity patterns along eleva- tional transects. Using a multi-taxa approach, we investigated the effects of elevation, area, habitat and soil characteristics on species richness, individual abundance and species com- position of six groups of ground-dwelling arthropods along four transect lines in the Swiss National Park and its surroundings (Eastern Alps). Spiders, millipedes, centipedes, ants, ground beetles and rove beetles were sampled using standardized methods (pitfall traps, cardboard traps, visual search) in 65 sites spanning an elevational range from 1800 to 2750 m a.s.l.. A total of 14,782 individuals comprising 248 species were collected (86 spider, 74 rove beetle, 34 ground beetle, 21 millipede, 19 centipede and 14 ant species). Linear mixed model-analysis revealed that rarefied species richness in five out of the six arthropod groups was affected by elevation (the quadratic term of elevation provided the best fit in most cases). We found three different patterns (linear decrease in centipedes, low elevation pla- teau followed by a decrease in ants and rove beetles, and midpoint peak in spiders and milli- pedes). These patterns were only partially mirrored when considering individual abundance. Elevation influenced species composition in all groups examined. Overall, elevation was the most important factor explaining the diversity patterns, while most local habitat and soil char- acteristics have little influence on these patterns. Our study supports the importance of using multi-taxa approaches when examining effects of elevational gradients. Considering only a single group may result in misleading findings for overall biodiversity.

2021  Saproxylic insects and fungi in deciduous forests along a rural-urban gradient — Meyer S, Rusterholz H-P & Baur B — Ecology and Evolution 11: 1634–1652   doi> 10.1002/ece3.7152 

Urbanization is increasing worldwide and is regarded a major threat to biodiversity in forests. As consequences of intensive human use, the vegetation structure of naturally growing urban forests and their amount of deadwood can be reduced. Deadwood is an essential resource for various saproxylic insects and fungi. We assessed the effects of urbanization and forest characteristics on saproxylic insects and fungi. We exposed standardized bundles consisting of each three freshly cut beech and oak branches in 25 forests along a rural–urban gradient in Basel (Switzerland). After an exposure of 8 months, we extracted the saproxylic insects for 10 months using an emergence trap for each bundle. We used drilling chips from each branch to determine fungal operational taxonomic units (OTUs). In all, 193,534 insect individuals emerged from the experimental bundles. Our study showed that the abundance of total saproxylic insects, bark beetles, longhorn beetles, total flies, moths, and ichneumonid wasps decreased with increasing degree of urbanization, but not their species richness. However, the taxonomic composition of all insect groups combined was altered by wood moisture of branches and that of saproxylic beetles was influenced by the degree of urbanization. Unexpectedly, forest size and local forest characteristics had a minor effect on saproxylic insects. ITS (internal transcribed spacer of rDNA) analysis with fungal specific primers revealed a total of 97 fungal OTUs on the bundles. The number of total fungal OTUs decreased with increasing degree of urbanization and was affected by the volume of naturally occurring fine woody debris. The composition of fungal OTUs was altered by the degree of urbanization and pH of the branch wood. As a consequence of the altered compositions of saproxylics, the association between total saproxylic insects and fungi changed along the rural–urban gradient. Our study shows that urbanization can negatively impact saproxylic insects and fungi.

Keywords: beetles - fine woody debris - flies - forest size - urbanization

2021  Integrated modelling of insect population dynamics at two temporal scales — Dennis EB, Kéry M, Morgan BJT, Coray A, Schaub M & Baur B — Ecological Modelling 441: 109408   doi> 10.1016/j.ecolmodel.2020.109408 

Population size of species with birth-pulse life-cycles varies both within and between seasons, but most population dynamics models assume that a population can be characterised adequately by a single number within a season. However, within-season dynamics can sometimes be too substantial to be ignored when modelling dynamics between seasons. Typical examples are insect populations or migratory animals. Numerous models for only between-season dynamics exist, but very few have combined dynamics at both temporal scales.
In a new approach, we extend appreciably the models of Dennis et al. (2016b): we show how to adapt them for a generation time > 1 year and fit an integrated population model for multiple data types, by maximising a joint likelihood for population counts of unmarked individuals and capture–recapture data from a study with marked individuals. We illustrate the approach using annual monitoring data for the endangered flightless beetle Iberodorcadion fuliginator from 18 populations in the Upper Rhine Valley for 1998–2016, with a 2-year life cycle. Standard likelihood methods are used for model fitting and comparison, and a concentrated (profile) likelihood approach provides computational efficiency.
Additional information from the capture–recapture data makes the population model more robust and, importantly, enables true, rather than relative, abundance to be estimated. A dynamic stopover model provides estimates of both survival and phenology parameters within a season, and also of productivity between seasons. For I. fuliginator, we demonstrate a population decline since 1998 and how this links with productivity, which is affected by temperature. A delayed mean emergence date in recent years is also shown.
A main point of interest is the focus on the two temporal scales at which perhaps most animal populations vary: in the short-term, a population is seldom truly closed within a single season, and in the long-term (between seasons) it never is. Hence our models may serve as a template for a general description of population dynamics in many species. This includes rare species with limited data sets, for which there is a general lack of population dynamic models, yet conservation actions may greatly benefit from this kind of models.

Keywords: beetle - endangered - Iberodorcadion fuliginator - integrated population model - multi-scale population dynamics - population model

2021  Naturschutzbiologie — Baur B — UTB GmbH Stuttgart, 440 Seiten

Naturschutzbiologie ist eine relativ junge wissenschaftliche Disziplin, deren Ziel die Erarbeitung der Grundlagen für die Erhaltung und Förderung der biologischen Vielfalt (Biodiversität) und der Ökosystemleistungen ist. Dieses Lehrbuch behandelt die wichtigsten Aspekte der Naturschutzbiologie, stellt neue Ergebnisse der Forschung vor und zeigt deren Anwendungsmöglichkeiten für den praktischen Naturschutz auf.
«Naturschutzbiologie» richtet sich an Bachelor- und Masterstudierende der Biologie, der Landschaftsplanung, Forstwissenschaften und (Bio-)Geografie. Das Lehrbuch dient auch der Weiterbildung von in den Bereichen «Naturschutz» und «Landschaftsplanung» tätigen Personen und bietet aktiven Naturschützern einen guten Überblick.

2021  Owners' perceptions do not match actual ground-dwelling invertebrate diversity in their gardens — Braschler B, Zwahlen V, Gilgado José D , Rusterholz H-P & Baur B — Diversity 13: 189   doi> 10.3390/d13050189 

Urban gardens are important for human well-being, biodiversity and other ecosystem functions. Biodiversity-promoting initiatives would benefit from their owners being aware of the state of biodiversity in their gardens. We examined whether garden owners' perceptions match actual biodiversity in their gardens and whether perceptions are influenced by the owners' ecological knowledge. We used a structured interview to assess the motivations and biodiversity knowledge of owners of 33 domestic gardens in the city of Basel (Switzerland) and related them to a survey of native plants and several groups of ground-dwelling invertebrates in their gardens. Owners showed different priorities, with promotion of habitat for biodiversity, receiving, on average, higher scores than cultivation, recreation and garden designing. Owners prioritizing biodiversity promotion had gardens with high habitat richness. The garden owners' perceptions of both native plant and overall invertebrate diversity were not correlated with actual diversity data for native plants and ground-dwelling invertebrates. The perceptions of the abundance of invertebrate groups by garden owners with good biodiversity knowledge were not more accurate than those from owners with less knowledge. Despite their willingness, many owners do not know all the opportunities to promote biodiversity. Initiatives to further biodiversity-friendly gardening should thus transfer knowledge.

Keywords: ants - beetles - biodiversity - ecological knowledge - gastropods - millipedes - private domestic gardens - spiders - urbanization - woodlice

2021  Single versus repeated human trampling events: Responses of ground vegetation in suburban beech forests — Rusterholz H-P, Weisskopf-Kissling M & Baur B — Applied Vegetation Science 24: e12604   doi> 10.1111/avsc.12604 

Forests provide important ecosystem services and are often the only natural areas that are freely accessible to the public for outdoor recreation. Large numbers of forest visitors can cause severe damage to forest ecosystems, which in turn can affect the ecosystem functioning. We aimed to assess whether experimental short-term and long-term trampling affect the ground vegetation in deciduous forests and its recovery to a different extent.
Beech forests in northwestern Switzerland.
We used a standard experimental trampling procedure to simulate single and repeated human trampling events of different intensity. Experimental trampling of different intensity was conducted on a single day (single trampling) or on five days at intervals of four weeks (repeated trampling) in three suburban beech forests on different soil types. We recorded the cover, height, species density and species composition of the ground vegetation in the trampling lanes. We also assessed the recovery of the ground vegetation one and two years after trampling.
Trampling intensity and the type of trampling (single vs repeated) affected the ground vegetation in the three forests. Vegetation cover, plant height and species density all decreased with increasing trampling intensity, but to a different extent in the three forests. Most vegetation characteristics were more severely affected by repeated trampling than single trampling of equal intensity. A longer trampling period strengthened the effects of trampling on ground vegetation, except in one forest. Two years after experimental trampling, most vegetation characteristics still differed from those of undisturbed ground vegetation.
Our study revealed that both trampling intensity and the temporal distribution of trampling influenced the ground vegetation in temperate forests. We provide evidence that the temporal distribution of human trampling events is an important factor, which has to be considered in management decisions for natural beech forests.

2021  Functional diversity and habitat preferences of native grassland plants and ground-dwelling invertebrates in private gardens along an urbanization gradient — Braschler B, Gilgado JD, Rusterholz H-P, Buchholz S, Zwahlen V & Baur B — Ecology and Evolution 11: 17043–17059   doi> 10.1002/ece3.8343 

Urbanization is occurring around the globe, changing environmental conditions and influencing biodiversity and ecosystem functions. Urban domestic gardens represent a small-grained mosaic of diverse habitats for numerous species. The challenging conditions in urban gardens support species possessing certain traits, and exclude other species. Functional diversity is therefore often altered in urban gardens. By using a multi-taxa approach focused on native grassland plants and ground-dwelling invertebrates with overall low mobility (snails, slugs, spiders, millipedes, woodlice, ants, rove beetles), we examined the effects of urbanization (distance to city center, percentage of sealed area) and garden characteristics on functional dispersion, functional evenness, habitat preferences and body size. We conducted a field survey in 35 domestic gardens along a rural–urban gradient in Basel, Switzerland. The various groups showed different responses to urbanization. Functional dispersion of native grassland plants decreased with increasing distance to the city center, while functional dispersion of ants decreased with increasing percentage of sealed area. Functional evenness of ants increased with increasing distance to the city center and that of rove beetles decreased with increasing percentage of sealed area. Contrary to our expectation, in rove beetles, the proportion of generalists decreased with increasing percentage of sealed area in the surroundings, and the proportion of species preferring dry conditions increased with increasing distance to the city center. Body size of species increased with distance to city center for slugs, spiders, millipedes, ants, and rove beetles. Local garden characteristics had few effects on functional diversity and habitat preferences of the groups examined. Our study supports the importance of using multi-taxa approaches when examining effects of environmental change on biodiversity. Considering only a single group may result in misleading findings for overall biodiversity. The ground-dwelling invertebrates investigated may be affected in different ways from the more often-studied flying pollinators or birds.

2020  Successful restoration of abandoned terraced vineyards and grasslands in Southern Switzerland — Rusterholz H-P, Binggeli D & Baur B — Basic and Applied Ecology 42: 35–46   doi> 10.1016/j.baae.2019.07.002 

Extensively managed semi-natural grasslands represent species-rich habitats and therefore play a key role for the maintenance of biodiversity in agricultural areas. In marginal and poorly accessible areas, the traditional management of grassland is frequently abandoned, which leads to the spread of forest. In Southern Switzerland, terraced vineyards (a special grassland type) and terraced grasslands are part of the cultural heritage and local biodiversity hotspots. Yet, many of them are overgrown by forest. In the past years, several abandoned terraced vineyards and grasslands have been restored by removing the forest, rebuilding the walls and re-introducing the traditional management. We examined restoration success by assessing plant species richness, diversity and species composition in both the aboveground vegetation and soil seed bank in (1) restored, (2) abandoned for 25–50 years, and (3) permanently used areas of six terraced vineyards and six terraced grasslands. Plant species richness and diversity were reduced and species composition altered in the aboveground vegetation of abandoned vineyards and grasslands compared to the permanently used and restored ones. However, species richness, Shannon-diversity and species composition of the aboveground vegetation did not differ between restored and permanently used areas, indicating a successful restoration of the vegetation 10–15 years after restoration. In abandoned vineyards, species richness of plants emerging from the soil seed bank was slightly higher than in permanently used and restored vineyards. No difference in seedling species richness was found between abandoned, permanently used and restored terraced grasslands. Our results showed that the soil seed bank played a minor role for the re-establishment of the above-ground vegetation. We assume that the large species pool in the surroundings and the presence of dispersal vectors are essential for the successful passive restoration of abandoned grassland in this region.

Keywords: passive restoration - semi-natural grassland - soil seed bank - traditional management

2020  Urbanisation and forest size affect the infestation rates of plant-galling arthropods and damage by herbivorous insects — Meyer S, Rusterholz H-P & Baur B — European Journal of Entomology 117: 34–38   doi> 10.14411/eje.2020.004 

Urbanisation is increasing globally and is considered to be a main driver of environmental change. Urbanisation-related factors include reduced habitat size and increased spatial isolation of the remaining habitats. As a consequence, the dynamics of plant and animal populations may change, which in turn might influence the quality and quantity of plant resources. Thus, urbanisation has the potential to disturb plant-animal interactions such as herbivory or galling. In the urban-rural setting of Basel (Switzerland), we aimed to assess whether the degree of urbanisation and forest size influence plant-galling infestation rates and leaf damage by mining and chewing arthropods on three tree species (sycamore, beech, and ash). We recorded species-specific responses to the degree of urbanisation and forest size. Gall infestation rate on sycamore leaves was affected by urbanisation but not by forest size. In contrast, gall infestation rates of beech gall midges responded sensitively to increasing urbanisation and decreasing forest size. The total leaf area damage caused by mining and chewing arthropods on sycamore was influenced by urbanisation and increased with increasing forest size. Leaf area damage by miners in beech tended to be affected by the degree of urbanisation, but not in ash. Urbanisation and forest size have the potential to alter herbivorous insect abundances. However, the effects depend on tree species and herbivore guild.

Keywords: urbanisation - forest size - arthropods - insects - herbivory - galls - parasitoid - chewing - mining

2020  Factors contributing to the decline of an endangered flightless longhorn beetle: a 20-year study — Baur B, Coray A, Lenzin H & Schmera D — Insect Conservation and Diversity 13: 175–186   doi> 10.1111/icad.12402 

1. World-wide decreases of insect abundance and diversity are of major concern because of their importance for ecosystem functioning and the stability of ecosystems. Various studies reported dramatic declines of butterflies, wild bees and beetles in agricultural areas. Yet, evidence for decreasing abundance in cryptic insect species is scarce.
2. Using a transect-count technique, we monitored the relative population size of the endangered flightless grassland longhorn beetle Iberodorcardion fuliginator in 13 dry, semi_natural grassland sites in the border region of Switzerland, France, and Germany at yearly intervals over 20 years (1999–2018). To disentangle potential causes for changes in I. fuliginator abundance over time, we recorded quantitatively the plant communities in all sites in 2004 and 2017 and changes in other habitat characteristics.
3. We found that the overall abundance of I. fuliginator individuals decreased by 90% over 20 years: at one site the population went extinct, at five sites the populations were critically decreasing, at four sites the populations were decreasing and at only three sites population size remained stable.
4. Linear models revealed that the factor ‘change in plant species composition’ is the main driver for the decrease in beetle abundance. Alternative models indicated that – in addition to vegetation changes – area of suitable habitat and low heat load affected the probability of decreasing population size.
5. Our study shows that gradual habitat deterioration measured as reduction in grass cover and change in plant species composition negatively affect the abundance of the highly specialised beetle I. fuliginator.

Keywords: agricultural intensification - Cerambycidae - habitat fragmentation - Iberodorcadion fuliginator - insect decline - long-term monitoring - semi-natural grasslands - species conservation

2020  Leaf litter decomposition and litter fauna in urban forests: Effect of the degree of urbanisation and forest size — Meyer S, Rusterholz H-P, Salamon J-A & Baur B — Pedobiologia 78: 150609   doi> 10.1016/j.pedobi.2019.150609 

Urbanisation is an important driver of environmental change and has the potential to alter the functioning of ecosystem processes. In urban forests, a key ecosystem process is litter decomposition, which is driven by the litter quality and composition of litter fauna. We examined whether the degree of urbanisation and forest size influence litter decomposition rates by the mesofauna in Basel (Switzerland). In order to assess the impact of the litter mesofauna on decomposition rates, we exposed litterbags with three mesh sizes (100__m, 2_mm, and 4_mm) filled with a mixture of Acer pseudoplatanus, Fagus sylvatica, and Fraxinus excelsior litter for a period of 9 months in 17 forests of different size located in areas with different degrees of urbanisation. We recovered the litterbags after 3, 6, and 9 months, extracted the fauna and assessed the decomposition rates. We found that litter decomposition rates were negatively affected by the degree of urbanisation after 6 months, but not impacted by forest size. In terms of litter fauna, oribatid mites and Collembola were differently affected by urbanisation. Oribatid mites were most frequent in forests in moderately urbanised areas, whereas Collembola were more abundant in forests in highly urbanised areas. Abundances of Acari and Oribatida were lowest in medium-sized forests, while the abundance of Collembola was highest in large forests. Collembola species composition did not shift with urbanisation. Considering Collembola traits, species with globular bodies were most abundant in forests of medium-size and situated in low urbanised areas, whereas species with an eudaphic life form tended to be less abundant in small forests. We showed that urbanisation and forest size have the potential to impact litter fauna abundance and species with certain morphological and life form traits, which may alter the important ecosystem service of litter decomposition.

Keywords: Acari - oribatid mites - collembola - species composition - traits - urban ecology

2020  The function of a set-aside railway bridge in connecting urban habitats for animals: a case study — Braschler B, Dolt C & Baur B — Sustainability 12: 1194   doi> 10.3390/su12031194 

As elements of green infrastructure, railway embankments are important corridors in urban environments connecting otherwise isolated habitat fragments. They are interrupted when railways cross major roads. It is not known whether dispersing animals use railway bridges to cross roads. We examined the function of a set-aside iron-steel railway bridge crossing a 12 m wide road with high traffic density in Basel (Switzerland) for dispersing animals. We installed drift fences with traps on a single-track, 32 m long and 6 m wide railway bridge with a simple gravel bed, and collected animals daily for 9 months. We captured more than 1200 animals crossing the bridge: small mammals, reptiles and amphibians as well as numerous invertebrates including snails, woodlice, spiders, harvestmen, millipedes, carabids, rove beetles and ants. For some animals it is likely that the gravel bed, at least temporarily, serves as a habitat. Many animals, however, were apparently dispersing, using the bridge to cross the busy road. We found season- and daytime -dependent differences in the frequency the bridge was used. Our findings indicate an important function of a set-aside railway bridges for connecting urban habitats. As most animal dispersal was recorded during the night, railway bridges with no (or little) traffic during the night may also contribute to animal dispersal. As important elements of green infrastructure, set-aside railway bridges should be considered in future urban planning.

Keywords: biodiversity - corridors - dispersal - greenways - green infrastructure - habitat connectivity - habitat fragmentation - invertebrates - urbanization - urban planning

2020  Anotylus politus (Erichson, 1840) (Coleoptera, Staphylinidae) neu für die Fauna der Schweiz — Feldmann B, Buchholz S, Gilgado JD, Baur B & Braschler B — Entomo Helvetica 13: 153–154

A single specimen of Anotylus politus was captured in Riehen (BS) in 2014. This is the first record of the species in Switzerland.

Keywords: Anotylus politus - Coleoptera - faunistics - new record - Staphylinidae - Switzerland

2020  Ground-dwelling invertebrate diversity in domestic gardens along a rural-urban gradient: Landscape characteristics are more important than garden characteristics — Braschler B, Gilgado JD, Zwahlen V, Rusterholz H-P, Buchholz S & Baur B — PLOS ONE 15: e0240061   doi> 10.1371/journal.pone.0240061 

Urbanisation is increasing worldwide and is regarded a major driver of environmental change altering local species assemblages. Private domestic gardens contribute a significant share of total green area in cities, but their biodiversity has received relatively little attention. Previous studies mainly considered plants, flying invertebrates such as bees and butterflies, and birds. By using a multi-taxa approach focused on less mobile, ground-dwelling invertebrates, we examined the influence of local garden characteristics and landscape characteristics on species richness and abundance of gastropods, spiders, millipedes, woodlice, ants, ground beetles and rove beetles. We assume that most of the species of these groups are able to complete their entire life cycle within a single garden. We conducted field surveys in thirty-five domestic gardens along a rural-urban gradient in Basel, Switzerland. Considered together, the gardens examined harboured an impressive species richness, with a mean share of species of the corresponding groups known for Switzerland of 13.9%, ranging from 4.7% in ground beetles to 23.3% in woodlice. The overall high biodiversity is a result of complementary contributions of gardens harbouring distinct species assemblages. Indeed, at the garden level, species richness of different taxonomical groups were typically not inter-correlated. The exception was ant species richness, which was correlated with those of gastropods and spiders. Generalised linear models revealed that distance to the city centre is an important driver of species richness, abundance and composition of several groups, resulting in an altered species composition in gardens in the centre of the city. Local garden characteristics were important drivers of gastropod and ant species richness, and the abundance of spiders, millipedes and rove beetles. Our study shows that domestic gardens make a valuable contribution to regional biodiversity. Thus, domestic urban gardens constitute an important part of green infrastructure, which should be considered by urban planners.

2020  Notwendigkeit eines Brückenschlags zwischen Wissenschaft und Praxis im Naturschutz – Chancen und Herausforderungen — Riecken U, Ammer C, Baur B, Bonn A, Diekötter T, Hotes S, Krüß A, Klimek S, Leyer I, Werk K, Ziegenhagen B & Farwig N — Natur und Landschaft 95: 364–371   doi> 10.17433/8.2020.50153829.364-371 

Successful action in conservation calls for close exchange and effective feedback between science and practitioners at all levels. However, many examples and experiences indicate that this mutual exchange does not function optimally nor according to requirements. From the authors' point of view, there is a need for a new “bridging” in conservation in order to optimise the transfer of evidence-based research results into practice and, vice versa, of practical requirements into science. Based on an analysis of the current challenges and causes in this context, this paper derives stakeholder-specific solutions to achieve a new bridging in conservation and presents them for discussion. In addition, it presents four best-practice examples. Conservation science must take greater account of practical requirements in conservation. Similarly, applied research addressing these requirements must gain more recognition by the scientific community. At the same time, the discussion is hoped to prompt con- servation practitioners to base their actions more strongly on evidence and to seek cooperation with the scientific community even more actively.

Keywords: conservation practice - evidence - conservation research - centre of competence - research funding - academic training

2020  Plant-mycorrhiza association in urban forests: Effects of the degree of urbanisation and forest size on the performance of sycamore (Acer pseudoplatanus) saplings — Rusterholz H-P, Studer M, Zwahlen V & Baur B — Urban Forestry & Urban Greening 56: 126872   doi> 10.1016/j.ufug.2020.126872 

Environmental change as result of urbanisation can influence soil microbial communities in green areas. In cities, forests are among the most frequent types of green areas and provide a wide variety of ecosystem services for the residents, such as air cleaning, nutrient cycling and area for recreational activities. Mycorrhizal fungi play an important role for the establishment of trees and therefore for the natural regeneration of forests. We examined the effect of urbanisation on the arbuscular mycorrhizal (AM) fungal symbiosis and performance of Acer pseudoplatanus saplings in a controlled field experiment in forests situated in the city of Basel and its suburbs in Switzerland. A total of 660 one-year-old A. pseudoplatanus saplings were planted in plots in 11 forests, which differed in degree of urbanisation in the surroundings and size. Saplings including their full root systems were harvested after 4, 6 and 13 months. AM fungal colonisation was 15–45 % lower on roots of saplings growing in forests located in areas with a high degree of urbanisation than that on sapling roots in forests in less urbanised areas. Furthermore, AM fungal colonisation of saplings decreased with decreasing forest size. Sapling survival was not influenced by urbanisation, but by forest size. In particular, sapling survival was reduced in small and medium-sized forests. Sapling survival also increased with increasing percentage of AM fungal colonisation after 13 months. These urbanisation- and forest-size induced changes became more pronounced with the time elapsed since the saplings were planted. Our findings demonstrate the negative impact of urbanisation on AM fungal symbiosis and the performance of A. pseudoplatanus saplings and indicate that urbanisation is a threat for the long-term maintenance of intact small urban forests.

Keywords: arbuscular mycorrhiza - forest ecosystem - plant-soil feedback - survival - urbanisation

2019  Defoliation of wild native box trees (Buxus sempervirens): Does box rust (Puccinia buxi) infection influence herbivory, survival and growth of the invasive Cydalima perspectalis? — Baur B, Jung J & Rusterholz H-P — Journal of Applied Entomology 143: 766–775   doi> 10.1111/jen.12640 

The invasive box-tree moth Cydalima perspectalis causes damage to horticultural box trees (Buxus spp.) in private gardens and parks in Europe and defoliation of large areas of European native box trees Buxus sempervirens, which grow in the understorey of deciduous forests. In some parts of their distribution area, wild native box trees are infected by the box rust Puccinia buxi, a fungus which does not occur in the native range of C. perspectalis. We examined whether the infection of P. buxi deters grazing by C. perspectalis in 31 wild box-tree stands in forests in north-western Switzerland and south-western Germany. On average, 82.4% of the box trees were infested by P. buxi (among-site variation 20%–100%), or 18.5% of their leaves. Linear mixed-effect (LME) models revealed that the percentage of rust-infected leaves was influenced by the local box-tree density and the slope aspect of the forest site. 9.5% of the leaves showed grazing damage by C. perspectalis. LME showed that the percentage of leaves with grazing damage was affected by the elevation of the site and the percentage of rust-infected leaves. The effect of box rust infection on food choice and larval performance (survival and growth rate) was examined in two experiments. In food-choice tests, larvae of C. perspectalis did not show any preference for uninfected or rust-infected box_tree leaves and consumed similar amounts of leaf tissue of either type. However, when larvae were reared on leaves with three different degrees of P. buxi-infection (and uninfected leaves as control), both survival and growth rate decreased with increasing degree of rust infection. This indicates that larval performance of C. perspectalis is reduced by the box rust. In the case of an outbreak of C. perspectalis, however, larvae may indiscriminately defoliate wild box trees.

Keywords: box-tree moth - food choice - herbivory - host plant - larval performance - pest species

2019  The annual invasive plant Impatiens glandulifera reduces hyphal biomass of soil fungi in deciduous forests — Gaggini L, Rusterholz H-P & Baur B — Fungal Ecology 39: 242–249   doi> 10.1016/j.funeco.2018.12.004 

Soil fungi play a crucial role in ecosystem functioning and there is increasing evidence that exotic plants invading forests can affect soil fungal communities. We examined potential effects of the invasive plant Impatiens glandulifera on hyphal biomass of ectomycorrhizal fungi, their genetic diversity and the diversity of other soil fungi in deciduous forests in Switzerland. We compared invaded patches with patches where I. glandulifera had been removed, by establishing pairs of 3-m long transect lines at the edge of seven areas of either type. Along the transects we assessed the length of ectomycorrhizal fungal hyphae using the 'ingrowth mesh bag method', and used terminal restriction fragment length polymorphism (T-RFLP) analysis to examine fungal genetic diversity. The invasive plant reduced fungal hyphal biomass by 30-80%: the reduction was largest in the centre of the patch. I. glandulifera did not alter fungal richness, but affected the composition of fungal communities. This is probably the result of a decrease of mycorrhizal fungi, coupled with an increase of saprotrophic fungi. Our findings demonstrate the adverse impacts of an annual invasive plant species on both fungal hyphal biomass and the composition of soil fungal communities. This may negatively affect forest nutrient and carbon cycling, soil stability and the functionality of the fungal community, with major consequences for forest ecosystem functioning.

Keywords: biological invasions - ectomycorrhizal hyphae - extramatrical mycelium - hyphal length - ingrowth mesh bags - soil fungi - T-RFLP

2019  The invasion of an annual exotic plant species affects the above- and belowground plant diversity in deciduous forests to a different extent — Gaggini L, Rusterholz H-P & Baur B — Perspectives in Plant Ecology, Evolution and Systematics 38: 74–83   doi> 10.1016/j.ppees.2019.04.004 

Invasive plant species can significantly affect native biodiversity and ecosystem functioning. Even though the majority of ecosystems have more than 50% of the plant biomass belowground, most studies investigating the effects of invasive species on plant diversity focus on the aboveground vegetation. DNA-based methods allow the determination of belowground plant structures. Using these techniques, we examined potential effects of the annual invasive plant Impatiens glandulifera on both the above- and belowground plant species richness and composition in mixed deciduous forests in Northwestern Switzerland. We established 24 plots in three forest areas invaded by I. glandulifera and in three adjacent forest areas, which were not yet invaded. In each plot, we determined plant species richness and abundance in the aboveground vegetation, and collected soil samples at depths of 0–10_cm and 11–20_cm to determine belowground plant species richness. We extracted DNA from fine roots in the soil samples and applied the FAFLP technique (fluorescent amplified fragment length polymorphism) for two different regions of the chloroplast DNA (trnL-trnF intergenic spacer and P6 loop). We established a reference library for all plant species occurring in the study areas to identify the species present in mixed-root samples. Our results showed that I. glandulifera caused shifts in both the above- and belowground plant species composition. Plant species richness was reduced by 30% aboveground in invaded plots, but not belowground in the same plots. Many geophytes and woody species were found belowground but not aboveground in invaded plots. Root biomass was reduced by 35–55% in invaded plots, most probably due to allelopathic compounds released by the invasive plant into the soil. Our field survey shows that above- and belowground plant communities respond differently to the invasion of an annual plant species, and that the invasive species can negatively affect forest ecosystem functions, by reducing root biomass and altering plant species richness and composition.

Keywords: biological invasions - fluorescent amplified fragment length polymorphism (FAFLP) - Impatiens glandulifera - mixed root samples - species identification - trnL intron

2018  The invasive plant Impatiens glandulifera affects soil fungal diversity and the bacterial community in forests — Gaggini L, Rusterholz H-P & Baur B — Applied Soil Ecology 124: 335–343   doi> 10.1016/j.apsoil.2017.11.021 

Invasive plants may severely impact native biodiversity and ecosystem functioning. We examined potential effects of the invasive annual plant Impatiens glandulifera Royle on soil fungal and bacterial communities in temperate forests. Using a space-for-time approach, we established 72 plots in forest areas invaded by I. glandulifera and in forest areas, which were not yet invaded, equally distributed over three coniferous and three deciduous forests. In each plot, we determined plant species richness and abundance in the above-ground vegetation as well as the diversity and composition of the soil fungal community using T-RFLP analysis. Biolog Ecoplates were used to assess the activity of soil bacteria. The invasion of I. glandulifera caused significant shifts in plant species composition. Invaded plots were characterized by a higher diversity and an altered composition of the soil fungal community and by a lower soil bacterial activity in late spring. Carbon substrate utilization patterns of soil bacteria were also changed in invaded plots. Our experiment shows that I. glandulifera can modify soil fungal and bacterial communities, indicating an indirect effect of altered soil properties induced by the invasive plant, combined with the release of allelopathic compounds into the soil.

Keywords: annual exotic plant species - biological invasions - microbial activity - space-for-time substitution - soil fungal community

2018  Intensity-dependent impact of sport climbing on vascular plants and land snails on limestone cliffs — Schmera D, Rusterholz H-P, Baur A & Baur B — Biological Conservation 442: 63–70   doi> 10.1016/j.biocon.2018.05.012 

Limestone cliffs in the Jura Mountains harbour species-rich plant and animal communities including rare species. Sport climbing has recently increased in popularity in this habitat and several studies have reported damage to cliff biodiversity. However, so far how damage levels vary with climbing intensity has not been investigated. We evaluated the effects of climbing intensity on the diversity of vascular plants and land snails in 35 limestone cliff sectors in the Northern Swiss Jura Mountains. Mixed-effects models were used to examine whether species richness of plants and land snails differ between cliff sectors with low and high climbing intensity and unclimbed cliff sectors (controls) taking into account potential influences of cliff characteristics (aspect, cliff height, rock microtopography). At the cliff base, the best fit model revealed that plant species richness was affected by climbing intensity and cliff aspect. Plant species richness was reduced by 12.2% and 13.1%, respectively, in cliff sectors with low and high climbing intensity compared to unclimbed cliff sectors. On the cliff face, plant species richness was only influenced by climbing intensity (species richness reduction by 24.3% and 28.1%). Combining data from cliff base, face and plateau, the best fit model revealed that land snail species richness was only affected by climbing intensity (species richness reduction by 2.0% and 13.7%). In both organism groups, species composition was increasingly altered by increasing climbing intensity. Our study provides evidence that even low climbing intensity reduces cliff biodiversity and that damage becomes more pronounced with increasing climbing intensity.

2018  Invasion of the alien shrub Prunus laurocerasus in suburban deciduous forests: Effects on native vegetation and soil properties — Rusterholz H-P, Schneuwly J & Baur B — Acta Oecologia 92: 44–51   doi> 10.1016/j.actao.2018.08.004 

Most invading alien plants affect native biodiversity and ecosystem functioning. In a field survey, we assessed the impact of the invasive shrub Prunus laurocerasus on the native vegetation and soil properties in suburban deciduous forests in the region of Basel, Switzerland. We installed four pairs of plots in patches of P. laurocerasus and in adjacent not invaded areas in each of twelve forest areas. Native species richness, Shannon-diversity and species composition of the ground vegetation and shrub layer were assessed in each plot. Furthermore, in each plot we measured physical and soil chemical characteristics, enzyme activities and the carbon source utilization pattern of the soil microbial community using Ecoplates™. The maximum age of P. laurocerasus in each plot was determined using tree ring analysis, indicating the time elapsed since the invasive plant has established. A lower native plant species richness in both the ground vegetation and shrub layer was observed in plots with presence of P. laurocerasus. A different species composition of the ground vegetation was also found among plots with and without the invasive shrub. Plots invaded by P. laurocerasus had a lower soil moisture content than control plots. The intensity, diversity and substrate richness of the carbon sources were increased in soil from invaded plots compared to soil in control plots. However, the chemical soil characteristics examined and the activities of enzymes were not influenced by the invasive plant. The effects of P. laurocerasus became more pronounced with the time elapsed since the invasive plant has established. Thus, the removal of young P. laurocerasusindividuals would be an appropriate management practice for this invasive shrub species.

Keywords: alien shrub - soil enzyme - early invasion phase - ornamental plant

2018  Diverse effects of degree of urbanisation and forest size on species richness and functional diversity of plants, and ground surface-active ants and spiders — Melliger RL, Braschler B, Rusterholz H-P & Baur B — PLoS One 13: e0199245   doi> 10.1371/journal.pone.0199245 

Urbanisation is increasing worldwide and is regarded a major driver of environmental change altering local species assemblages in urban green areas. Forests are one of the most frequent habitat types in urban landscapes harbouring many native species and providing important ecosystem services. By using a multi-taxa approach covering a range of trophic ranks, we examined the influence of degree of urbanisation and forest size on the species richness and functional diversity of plants, and ground surface-active ants and spiders. We conducted field surveys in twenty-six forests in the urban region of Basel, Switzerland. We found that a species’ response to urbanisation varied depending on trophic rank, habitat specificity and the diversity indices used. In plants, species richness decreased with degree of urbanisation, whereas that of both arthropod groups was not affected. However, ants and spiders at higher trophic rank showed greater shifts in species composition with increasing degree of urbanisation, and the percentage of forest specialists in both arthropod groups increased with forest size. Local abiotic site characteristics were also crucial for plant species diversity and species composition, while the structural diversity of both leaf litter and vegetation was important for the diversity of ants and spiders. Our results highlight that even small urban forests can harbour a considerable biodiversity including habitat specialists. Nonetheless, urbanisation directly and indirectly caused major shifts in species composition. Therefore, special consideration needs to be given to vulnerable species, including those with special habitat requirements. Locally adapted management practices could be a step forward to enhance habitat quality in a way to maximize diversity of forest species and thus ensure forest ecosystem functioning; albeit large-scale factors also remain important.

2018  Genetic effects of anthropogenic habitat fragmentation on remnant animal and plant populations: a meta-analysis — Schlaepfer DR, Braschler B, Rusterholz H-P & Baur B — Ecosphere 9: e02488   doi> 10.1002/ecs2.2488 

Habitat loss and fragmentation are among the biggest threats to biodiversity. Anthropogenic habitat fragmentation leads to small and isolated remnant plant and animal populations. The combination of increased random genetic drift, inbreeding, and reduced gene flow may substantially reduce genetic variation of remnant populations. However, the magnitude of these responses may depend on several poorly understood factors including organism group, habitat type of both the fragment and the surrounding matrix, life-history traits, and time since fragmentation. We compiled data for 83 plant and 52 animal species and conducted a meta-analysis following best practices to evaluate how these factors mediate the effects of anthropogenic habitat fragmentation. We calculated 206 effect sizes as correlations between one of four measures of population-level genetic diversity and fragment area. All analyses were repeated using models of increasing complexity (traditional random-effects models, multilevel models accounting for non-independent data, and multilevel models additionally correcting for phylogenetic relatedness). We confirmed that anthropogenic habitat fragmentation has overall negative effects on genetic diversity of organisms. Our meta-analysis shows, however, that plant species responded in general stronger to fragmentation than animal species and that the largest negative impacts of fragmentation occurred in tropical and temperate forest fragments, surrounded by a non-forest matrix. In contrast, we found only weak responses in non-forest fragments. Genetic diversity measured as mean number of alleles (A) showed the strongest response to fragmentation. Expected heterozygosity (He) and percentage of polymorphic loci (PLP) showed similar but weaker responses. In contrast, our meta-analysis indicated that inbreeding (Fis) was not measurably affected by anthropogenic habitat fragmentation. Additionally, our models revealed that effects on genetic diversity became stronger with age of fragments: We found significant negative responses for fragments older than 50 yr but not for those more recently isolated. Our meta-analyses also showed that currently animals are underrepresented in the literature on genetic effects of anthropogenic fragmentation, as are certain geographical regions and habitat types. We expect that future field studies using state-of-the-art approaches will provide further evidence of negative genetic effects, which may reinforce the here reported patterns, even for groups not yet studied.

Keywords: allelic richness - forest fragmentation - genetic diversity - inbreeding - matrix habitat - phylogenetic models - time since fragmentation

2017  Dynamics of reintroduced populations of Oedipoda caerulescens (Orthoptera, Acrididae) over 21 years — Baur B, Thommen GH & Coray A — Journal of Insect Science 17: 10   doi> 10.1093/jisesa/iew102 

Conservation programs increasingly involve the reintroduction of animals which otherwise would not recolon- ize restored habitats. We assessed the long-term success of a project in which the Blue-winged grasshopper, Oedipoda caerulescens (L., 1758), was reintroduced to a nature reserve in Northwestern Switzerland, an alluvial gravel area where the species went extinct in the 1960s. In summer 1995, we released 110 individuals (50 fe- males and 60 males) and 204 individuals (101 females and 103 males) into two restored gravel patches with sparse vegetation. We used a transect count technique to assess the population size of O. caerulescens in the years 1995–2004 and 2015–2016 and recorded the area occupied by the species. At both release sites, the popu- lations persisted and increased significantly in size. Individuals that followed a newly created corridor estab- lished four new subpopulations. Seven years after reintroduction, O. caerulescens had reached a high abun- dance around the release sites and in the four colonized patches, indicating a successful project. At the same time, the dispersal corridor became increasingly overgrown by dense vegetation. Surveys 20 and 21 yr after introduction showed that the abundance of the Blue-winged grasshopper had strongly declined in the estab- lished subpopulations and moderately in the original release sites, owing to natural succession of the habitat and lack of disturbances, which reduced the area suitable for the species by 59%. Our study shows that reintro- ductions are unlikely to succeed without integration of long-term habitat management (in the present case maintenance of open ground).

Keywords: habitat restoration - propagule size - reintroduction - succession

2017  The database of the PREDICTS (Projecting Responses of Ecological Diversity in Changing Terrestrial Systems) project — Hudson LN, Newbold T, Contu S, Hill SLL, Lysenko I, De Palma A, Phillips HRP, Alhusseini TI, Bedford FE, Bennett DJ, Booth H, Burton VJ, Chng CWT, Choimes A, Correia DLP, Day J, Echeverría-Londoño S, Emerson SR, Gao D, Garon M, Harrison MLK, Ingram DJ, Jung M, Kemp V, Kirkpatrick L, Martin CD, Pan Y, Pask-Hale GD, Pynegar EL, Robinson AN, Sanchez-Ortiz K, Senior RA, Simmons BI, White HJ, Zhang H, Aben J, Abrahamczyk S, Adum GB, Aguilar-Barquero V, Aizen MA, Albertos B, Alcala EL, del Mar Alguacil M, Alignier A, Ancrenaz M, Andersen AN, Arbeláez-Cortés E, Armbrecht I, Arroyo-Rodríguez V, Aumann T, Axmacher JC, Azhar B, Azpiroz AB, Baeten L, Bakayoko A, Báldi A, Banks JE, Baral SK, Barlow J, Barratt BIP, Barrico L, Bartolommei P, Barton DM, Basset Y, Batáry P, Bates AJ, Baur B, Bayne EM, Beja P, Benedick S, Berg Å, Bernard H, Berry NJ, Bhatt D, Bicknell JE, Bihn JH, Blake RJ, Bobo KS, Bóçon R, Boekhout T, Böhning-Gaese K, Bonham KJ, Borges PAV, Borges SH, Boutin C, Bouyer J, Bragagnolo C, Brandt JS, Brearley FQ, Brito I, Bros V, Brunet J, Buczkowski G, Buddle CM, Bugter R, Buscardo E, Buse J, Cabra-García J, Cáceres NC, Cagle NL, Calviño-Cancela M, Cameron SA, Cancello EM, Caparrós R, Cardoso P, Carpenter D, Carrijo TF, Carvalho AL, Cassano CR, Castro H, Castro-Luna AA, Rolando CB, Cerezo A, Chapman KA, Chauvat M, Christensen M, Clarke FM, Cleary DFR, Colombo G, Connop SP, Craig MD, Cruz-López L, Cunningham SA, D'Aniello B, D'Cruze N, da Silva PG, Dallimer M, Danquah E, Darvill B, Dauber J, Davis ALV, Dawson J, de Sassi C, de Thoisy B, Deheuvels O, Dejean A, Devineau J-L, Diekötter T, Dolia JV, Domínguez E, Dominguez-Haydar Y, Dorn S, Draper I, Dreber N, Dumont B, Dures S, Dynesius M, Edenius L, Eggleton P, Eigenbrod F, Elek Z, Entling MH, Esler KJ, de Lima RF, Faruk A, Farwig N, Fayle TM, Felicioli A, Felton AM, Fensham RJ, Fernandez IC, Ferreira CC, Ficetola GF, Fiera C, Filgueiras BKC, Fırıncıoğlu HK, Flaspohler D, Floren A, Fonte SJ, Fournier A, Fowler RE, Franzén M, Fraser LH, Fredriksson GM, Freire Jr GB, Frizzo TLM, Fukuda D, Furlani D, Gaigher R, Ganzhorn JU, García KP, Garcia-R JC, Garden JG, Garilleti R, Ge B-M, Gendreau-Berthiaume B, Gerard PJ, Gheler-Costa C, Gilbert B, Giordani P, Giordano S, Golodets C, Gomes LGL, Gould RK, Goulson D, Gove AD, Granjon L, Grass I, Gray CL, Grogan J, Gu W, Guardiola M, Gunawardene NR, Gutierrez AG, Gutiérrez-Lamus DL, Haarmeyer DH, Hanley ME, Hanson T, Hashim NR, Hassan SN, Hatfield RG, Hawes JE, Hayward MW, Hébert C, Helden AJ, Henden J-A, Henschel P, Hernández L, Herrera JP, Herrmann F, Herzog F, Higuera-Diaz D, Hilje B, Höfer H, Hoffmann A, Horgan FG, Hornung E, Horváth R, Hylander K, Isaacs-Cubides P, Ishida H, Ishitani M, Jacobs CT, Jaramillo VJ, Jauker B, Hernández FJ, Johnson MF, Jolli V, Jonsell M, Juliani SN, Jung TS, Kapoor V, Kappes H, Kati V, Katovai E, Kellner K, Kessler M, Kirby KR, Kittle AM, Knight ME, Knop E, Kohler F, Koivula M, Kolb A, Kone M, Kőrösi Á, Krauss J, Kumar A, Kumar R, Kurz DJ, Kutt AS, Lachat T, Lantschner V, Lara F, Lasky JR, Latta SC, Laurance WF, Lavelle P, Le Féon V, LeBuhn G, Légaré J-P, Lehouck V, Lencinas MV, Lentini PE, Letcher SG, Li Q, Litchwark SA, Littlewood NA, Liu Y, Lo-Man-Hung N, López-Quintero CA, Louhaichi M, Lövei GL, Lucas-Borja ME, Luja VH, Luskin MS, MacSwiney MC, Maeto K, Magura T, Mallari NA, Malone LA, Malonza PK, Malumbres-Olarte J, Mandujano S, Måren IE, Marin-Spiotta E, Marsh CJ, Marshall EJP, Martínez E, Martínez Pastur G, Mateos DM, Mayfield MM, Mazimpaka V, McCarthy JL, McCarthy KP, McFrederick QS, McNamara S, Medina NG, Medina R, Mena JL, Mico E, Mikusinski G, Milder JC, Miller JR, Miranda-Esquivel DR, Moir ML, Morales CL, Muchane MN, Muchane M, Mudri-Stojnic S, Munira AN, Muoñz-Alonso A, Munyekenye BF, Naidoo R, Naithani A, Nakagawa M, Nakamura A, Nakashima Y, Naoe S, Nates-Parra G, Navarrete Gutierrez DA, Navarro-Iriarte L, Ndang'ang'a PK, Neuschulz EL, Ngai JT, Nicolas V, Nilsson SG, Noreika N, Norfolk O, Noriega JA, Norton DA, Nöske NM, Nowakowski AJ, Numa C, O'Dea N, O'Farrell PJ, Oduro W, Oertli S, Ofori-Boateng C, Omamoke Oke C, Oostra V, Osgathorpe LM, Otavo SE, Page NV, Paritsis J, Parra-H A, Parry L, Pe'er G, Pearman PB, Pelegrin N, Pélissier R, Peres CA, Peri PL, Persson AS, Petanidou T, Peters MK, Pethiyagoda RS, Phalan B, Philips TK, Pillsbury FC, Pincheira-Ulbrich J, Pineda E, Pino J, Pizarro-Araya J, Plumptre AJ, Poggio SL, Politi N, Pons P, Poveda K, Power EF, Presley SJ, Proença V, Quaranta M, Quintero C, Rader R, Ramesh BR, Ramirez-Pinilla MP, Ranganathan J, Rasmussen C, Redpath-Downing NA, Reid JL, Reis YT, Rey Benayas JM, Rey-Velasco JC, Reynolds C, Ribeiro DB, Richards MH, Richardson BA, Richardson MJ, Ríos RM, Robinson R, Robles CA, Römbke J, Romero-Duque LP, Rös M, Rosselli L, Rossiter SJ, Roth DS, Roulston TH, Rousseau L, Rubio AV, Ruel J-C, Sadler JP, Sáfián S, Saldaña-Vázquez RA, Sam K, Samnegård U, Santana J, Santos X, Savage J, Schellhorn NA, Schilthuizen M, Schmiedel U, Schmitt CB, Schon NL, Schüepp C, Schumann K, Schweiger O, Scott DM, Scott KA, Sedlock JL, Seefeldt SS, Shahabuddin G, Shannon G, Sheil D, Sheldon FH, Shochat E, Siebert SJ, Silva FAB, Simonetti JA, Slade EM, Smith J, Smith-Pardo AH, Sodhi NS, Somarriba EJ, Sosa RA, Soto Quiroga G, St-Laurent M-H, Starzomski BM, Stefanescu C, Steffan-Dewenter I, Stouffer PC, Stout JC, Strauch AM, Struebig MJ, Su Z, Suarez-Rubio M, Sugiura S, Summerville KS, Sung Y-H, Sutrisno H, Svenning J-C, Teder T, Threlfall CG, Tiitsaar A, Todd JH, Tonietto RK, Torre I, Tóthmérész B, Tscharntke T, Turner EC, Tylianakis JM, Uehara-Prado M, Urbina-Cardona N, Vallan D, Vanbergen AJ, Vasconcelos HL, Vassilev K, Verboven HAF, Verdasca MJ, Verdú JR, Vergara CH, Vergara PM, Verhulst J, Virgilio M, Van Vu L, Waite EM, Walker TR, Wang H-F, Wang Y, Watling JI, Weller B, Wells K, Westphal C, Wiafe ED, Williams CD, Willig MR, Woinarski JCZ, Wolf JHD, Wolters V, Woodcock BA, Wu J, Wunderle Jr JM, Yamaura Y, Yoshikura S, Yu DW, Zaitsev AS, Zeidler J, Zou F, Collen B, Ewers RM, Mace GM, Purves DW, Scharlemann JPW & Purvis A — Ecology and Evolution 7: 145–188   doi> 10.1002/ece3.2579 

The PREDICTS project—Projecting Responses of Ecological Diversity In Changing Terrestrial Systems (—has collated from published studies a large, reasonably representative database of comparable samples of biodiversity from multiple sites that differ in the nature or intensity of human impacts relating to land use. We have used this evidence base to develop global and regional statistical models of how local biodiversity responds to these measures. We describe and make freely available this 2016 release of the database, containing more than 3.2 million records sampled at over 26,000 locations and representing over 47,000 species. We outline how the database can help in answering a range of questions in ecology and conservation biology. To our knowledge, this is the largest and most geographically and taxonomically representative database of spatial comparisons of biodiversity that has been collated to date; it will be useful to researchers and international efforts wishing to model and understand the global status of biodiversity.

2017  Impact assessment of intense sport climbing on limestone cliffs: Response of rock-dwelling land snails — Baur B, Baur A & Schmera D — Ecological Indicators 72: 260–267   doi> 10.1016/j.ecolind.2016.07.003 

• The specialized cliff biota is increasingly disturbed by recreational activities.
• We used land snails as indicator group for assessing the impact of sport climbing.
• Rock climbing reduces the diversity and abundance of land snails living on cliffs.

Exposed limestone cliffs in the Swiss Jura Mountains harbour a diverse gastropod community with some rare species. Sport climbing has recently increased in popularity on these cliffs. We examined the effects of sport climbing and microtopographical features of rock faces on terrestrial gastropods by assessing species diversity and abundance on climbing routes and in unclimbed areas of seven isolated cliffs in the Northern Swiss Jura Mountains. We considered exclusively living individuals resting attached to rock faces. In total, 19 gastropod species were recorded. Six of them were specialized rock-dwelling species, whose individuals spend their entire life on rock faces, feeding on algae and lichens. Plots along climbing routes harboured fewer species of rock-dwelling snails as well as other gastropod species (usually living in the leaf litter layer at the cliffs’ base) than plots in unclimbed control areas. Similarly, both the density of individuals and frequency of occurrence in plots were reduced in both groups of snails on climbing routes. The complexity of the rock surface had little influence on the species richness and abundance of gastropods. Pyramidula pusilla, the species with the smallest shell and a preference to rest underneath overhangs, was less affected by sport climbing than snail species with larger shells and a preference to rest on exposed smooth rock surface. Our findings indicate land snail diversity and abundance are suitable indicators for impact assessment in rocky habitats. Future management plans and actions should therefore not only rely on plants; they ought to consider also gastropods and other invertebrates. Any management plan should include a comprehensive information campaign to show the potential impact of intensive sport climbing on the specialized flora and fauna with the aim of educating the climbers and increasing their compliance with such measures.

Keywords: biodiversity - climbing - disturbance - gastropod - impact assessment

2017  Settlements are a source for the spread of non-native plants into mixed deciduous suburban forests — Gaggini L, Rusterholz H-P & Baur B — Acta Oecologia 79: 18–25   doi> 10.1016/j.actao.2016.12.008 

• We conducted vegetation surveys in forests near to and far from settlements.
• Settlements are a source for the spread of non-native plants into suburban forests.
• Roads and gardens contribute to the establishment of non-native plants in forests.
Urbanization is considered as a major driver for biotic homogenization. Urbanization also promotes the dispersal of non-native species. This study examined the roles of suburban settlements and of the surrounding landscape composition for the spread of non-native plant species into adjacent mixed deciduous forests in Southern and Northwestern Switzerland. The number and abundance of native and non-native vascular plant species in both the ground vegetation and shrub layer were recorded in 15 forest sites situated adjacent to settlements and 15 control sites far from settlements. Various site and landscape characteristics were assessed in the surroundings (100 m radius) of the study sites. In both regions we found a higher number and larger abundance of non-native plant species in forest sites adjacent to settlements than in control forest sites. Furthermore, non-native plants were more frequently recorded close to roads and in sites surrounded by a large percentage cover of garden. All these effects were more pronounced in Southern Switzerland, a region with milder winter climate, than in Northwestern Switzerland. Our study showed that settlements are a source for the spread of non-native plant species into Central European suburban forests, and that the composition of the surrounding landscape matrix (e.g. traffic infrastructure, percentage cover of gardens) also affects the establishment of non-native plants.

Keywords: alien plants - deciduous forests - gardens - landscape matrix - Switzerland - urbanization

2017  Experimental evidence for a delayed response of the above-ground vegetation and the seed bank to the invasion of an annual exotic plant in deciduous forests — Rusterholz H-P, Küng J & Baur B — Basic and Applied Ecology 20: 19–30   doi> 10.1016/j.baae.2017.02.004 

Invasions by alien plants significantly affect native biodiversity and ecosystem functioning. We conducted a 5-year field experiment to investigate potential effects of the annual invasive plant Impatiens glandulifera on both the native above-ground vegetation and the soil seed bank in a deciduous forest in Switzerland. Eight years after the establishment of I. glandulifera, we set up plots in patches invaded by the alien plant, in plots from which the invasive plant had been manually removed and in plots which were not yet colonized by the invasive plant. We examined plant species richness, diversity and plant species composition in the above-ground vegetation and soil seed bank in all plots one year and five years after the initiation of the experiment. The 36 plots (3 plot types × 6 replicates × 2 sites) were equally distributed over two forest sites. Neither the native above-ground vegetation nor the soil seed bank was influenced by the presence of I. glandulifera one year after the start of the field experiment. After five years, however, plant species richness of both the above-ground vegetation and the soil seed bank was reduced by 25% and 30%, respectively, in plots invaded by the alien plant compared to plots from which I. glandulifera had been removed or uninvaded plots. Furthermore, plots invaded by the alien plant had a lower total seedling density (reduction by 60%) and an altered plant species composition in the soil seed bank compared to control plots. Our field experiment indicates that negative effects of the annual invasive plant on the native above-ground vegetation and soil seed bank of deciduous forests become visible with a delay of several years.

Keywords: annual invasive plant species - disturbance - Impatiens glandulifera - temperate deciduous forest - time-dependent

2017  Habitat- and matrix-related differences in species diversity and trait richness of vascular plants, Orthoptera and Lepidoptera in an urban landscape — Melliger RL, Rusterholz H-P & Baur B — Urban Ecosystems 20: 1095–1107   doi> 10.1007/s11252-017-0662-5 

Urban growth is considered to be a major driver of environmental change. Urbanisation can affect urban biodiversity in different ways. So far, most studies focused on the impact of urbanisation on single taxa in one habitat type. In this study, we used data of species inventories and GIS-based landscape elements to examine the effects of habitat size and landscape composition on the species diversity of three taxonomic groups (vascular plants, Orthoptera and Lepidoptera) in meadows and ruderal sites in the urban region of Basel, Switzerland. We also related the responses of three species traits (body size, dispersal ability and food specialisation) to habitat size in Orthoptera and Lepidoptera. We found that species of the different taxonomic groups differed in their response to habitat size and landscape composition both in meadows and ruderal sites depending on the traits examined. The species richness of Orthoptera and Lepidoptera was positively related to meadow size but not to the size of ruderal sites, while the opposite was true for plants. For Lepidoptera in ruderal sites, the percentage cover of ruderal area in the closer surroundings was a better predictor of species richness than habitat size per se. To sustain high levels of urban biodiversity, we recommend that urban planners develop adequate management strategies to satisfy the different requirements of various taxonomic groups and to increase the quality of green sites surrounding the target habitat.

Keywords: urbanisation - species–area relationship - grasshoppers - butterflies - plant functional richness 

2017  Ecosystem functioning in cities: Combined effects of urbanisation and forest size on early-stage leaf litter decomposition of European beech (Fagus sylvatica L.) — Melliger RL, Rusterholz H-P & Baur B — Urban Forestry and Urban Greening 28: 88–96   doi> 10.1016/j.ufug.2017.10.009 

Environmental changes associated with urbanisation can affect the functioning of ecosystem processes. In cities, forests are among the most frequent types of green areas and provide a wide range of ecosystem services including air cleaning, decomposition of leaf litter and recreation. The European beech (Fagus sylvatica) is a frequent and widespread deciduous tree in temperate forests in Central Europe. In this study, we examined the effects of urbanisation on decomposition processes of F. sylvatica leaves in different-sized forests in the urban region of Basel, Switzerland. We used standardised litterbags (mesh size: 2 mm) with F. sylvatica leaves to assess the impact of degree of urbanisation (indicated by the percentage cover of sealed area in the surroundings) and forest size on the early stage of leaf litter decomposition and seasonal microbial activity. We found combined effects of degree of urbanisation and forest size on the decomposition rate of leaf litter (klitter). Large forests showed the highest klitter in areas with sparse settlements and the lowest klitter in densely settled areas, whereas the opposite pattern was recorded for small and medium-sized forests. This indicates that abiotic and biotic forest characteristics of forests of similar size differently influenced klitter depending on the degree of urbanisation. Moisture content of litter was the best predictor of microbial activity, followed by forest size. We assume that factors acting at the landscape scale such as the degree of urbanisation might be too coarse to detect any differences in microbial activity. Our results revealed that even small urban forests contribute to this important ecosystem function. As decomposers are at the bottom of the food chain, management actions that support the biological activity in soil might be also beneficial for species at higher trophic ranks.

Keywords: decomposition rate - forest area - leaf chemical characteristics - microbial activity - plant diversity - temperate deciduous forests

2017  Bridging science and practice in conservation: Deficits and challenges from a research perspective — Farwig N, Ammer C, Annighöfer P, Baur B, Behringer D, Diekötter T, Hotes S, Leyer I, Müller J, Peter F, Riecken U, Bessel A, Thorn S, Werk K & Ziegenhagen B — Basic and Applied Ecology 24: 1–8   doi> 10.1016/j.baae.2017.08.007 

Biodiversity is being lost at alarming rates in spite of efforts to conserve ecosystems, species and genetic diversity. There is broad consensus that biodiversity conservation needs to become more effective, and this requires an analysis of the causes that have prevented previous efforts from reaching their goal. A lack of knowledge exchange and cooperation between science and practice has been identified as a key issue in this context. Scientific knowledge frequently does not find its way into conservation practice, and information requirements by practitioners are often not considered appropriately by scientists. Here, we summarize deficits and challenges in the relationship between science and practice in conservation and outline approaches to achieving more effective knowledge exchange and collaboration at the interface between both. We propose that existing platforms for communication need to be complemented by independent institutions in particular at national and sub-national levels to facilitate successful co-production of knowledge as a prerequisite for effective conservation measures.

Keywords: boundary institution - communication platform - knowledge exchange

2017  Erinnerungen an Pioniere des Schweizerischen Nationalparks — Baur B, Rohner J & Scheurer T (Red) — Nationalpark-Forschung in der Schweiz 107, Haupt Verlag, Bern, 163 Seiten

Die «Erinnerungen an Pioniere des Schweizerischen Nationalparks» sind ein Beitrag zur Geschichte des Schweizerischen Nationalparks, insbesondere zu dessen Forschungsgeschichte. Dem Ansatz der Oral History folgend erinnern sich heute lebende Personen an Persönlichkeiten, welche die Forschung im Nationalpark zum Teil über Jahrzehnte hinweg geprägt haben und deren Forschungsergebnisse auch heute noch wichtige Grundlagen für weitere Projekte bilden. Denn die Langzeitforschung, das Erfassen der natürlichen Veränderungen in einer vom Menschen weitgehend unberührten Landschaft, ist ein zentrales Anliegen der Forschung im Nationalpark.
Die Erinnerungen sind zum Teil sehr persönlich geprägt, deshalb aber nicht weniger wertvoll als rein biografische Fakten. Sie beschreiben die damaligen Rahmenbedingungen, geben Einblicke in die Motivation für die intensive Beschäftigung mit der Natur im Nationalpark und zeigen auf, dass hinter den publizierten Forschungsergebnissen immer auch Individuen stehen – Menschen mit ihrem besonderen Charakter, mit ihren Vorlieben und Abneigungen, mit ihren Ecken und Kanten.

2016  Multi-taxa impacts of urban sprawl on species richness – not only the built-up area matters — Concepción ED, Obrist MK, Moretti M, Altermatt F, Baur B & Nobis MP — Urban Ecosystems 19: 225–242   doi> 10.1007/s11252-015-0474-4 

Urban growth is a major factor of global environmental change and has important impacts on biodiversity, such as changes in species composition and biotic homogenization. Most previous studies have focused on effects of urban area as a general measure of urbanization, and on few or single taxa. Here, we analyzed the impacts of the different components of urban sprawl (i.e., scattered and widespread urban growth) on species richness of a variety of taxonomic groups covering mosses, vascular plants, gastropods, butterflies, and birds at the habitat and landscape scales. Besides urban area, we considered the average age, imperviousness, and dispersion degree of urban area, along with human population density, to disentangle the effects of the different components of urban sprawl on biodiversity. The study was carried out in the Swiss Plateau that has undergone substantial urban sprawl in recent decades.
Vascular plants and birds showed the strongest responses to urban sprawl, especially at the landscape scale, with non-native and ruderal plants proliferating and common generalist birds increasing at the expense of specialist birds as urban sprawl grew. Overall, urban area had the greatest contribution on such impacts, but additional effects of urban dispersion (i.e., increase of non-native plants) and human population density (i.e., increases of ruderal plants and common generalist birds) were found. Our findings support the hypothesis that negative impacts of urban sprawl on biodiversity can be reduced by compacting urban growth while still avoiding the formation of very densely populated areas.

Keywords: built-up area - biotic homogenization – imperviousness - human population density - time-lagged effects - urban dispersion

2016  Diverse effects of a seven-year experimental grassland fragmentation on major invertebrate groups — Braschler B & Baur B — PLOS ONE 11: e0149567   doi> 10.1371/journal.pone.0149567 
Artikel als pdf Datei herunterladen

Habitat fragmentation is a major driver of biodiversity loss, but observed effects vary and may depend on the group examined. Time since fragmentation may explain some differences between taxonomical groups, as some species and thus species composition respond with a delay to changes in their environment. Impacts of drivers of global change may thus be underestimated in short-term studies. In our study we experimentally fragmented nutrient-poor dry calcareous grasslands and studied the response of species richness, individual density and species composition of various groups of invertebrates (gastropods, ants, ground beetles, rove beetles, orthoptera, spiders, woodlice) in 12 small (1.5 m * 1.5 m) and 12 large (4.5 m * 4.5 m) fragments and their corresponding control plots after 7 years. We further examined responses to fragmentation in relation to body size and habitat preferences. Responses to fragmentation varied between taxonomical groups. While spider species richness and individual density were lower in fragments, the opposite was true for an orthopteran species and woodlice. Species composition and ß-diversity differed between fragments and control plots for some groups. However, the interaction treatment*plot size was rarely significant. Species with high occupancy rates in undisturbed control plots responded more negatively to the fragmentation, while species with large body size were relatively more abundant in fragments in some groups. No effect of the fragmentation was found for ants, which may have the longest lag times because of long-lived colonies. However, relationships between abundance and the species’ preferences for environmental factors affected by edge effects indicate that ant diversity too may be affected in the longer-term. Our results show the importance of considering different groups in conservation management in times of widespread fragmentation of landscapes. While species richness may respond slowly, changes in abundance related to habitat preferences or morphology may allow insights into likely long-term changes.

2016  Effects of road type and urbanization on the diversity and abundance of alien species in roadside verges in Western Siberia — Vakhlamova T, Rusterholz H-P, Kanibolotskaya Y & Baur B — Plant Ecology 217: 241–252   doi> 10.1007/s11258-016-0565-1 

The spread of alien plant species by vehicles profoundly affects the roadside vegetation. Roads with high traffic densities in urban regions may facilitate the invasion of alien plants. The present study examined the effects of road type and distance to the city centre on native and alien plant species in both the aboveground vegetation and soil seed bank of road verges in originally dry steppe grasslands in the surroundings of Pavlodar, Western Siberia, Kazakhstan. This region is characterized by a recent change of land use and rapidly expanding urbanization. Vegetation surveys were conducted at 12 sites distributed along roads with different traffic densities (national and local roads) and at two distances to the city centre (city edge and rural surroundings). The seedling-emergence method was used to examine the soil seed bank at each site. We found a larger percentage of alien species along national roads (42 % in the aboveground vegetation, 57 % in the soil seed bank) than along local roads (20 and 44 %, respectively), which can be explained by differences in traffic density, location from which the vehicles come and habitat conditions. More alien species were found in the road verges at the city edge than in the rural surroundings along both road types, probably due to the spread of propagules from residential areas. Our study demonstrates that national roads are important pathways for the introduction of alien species in this Western Siberian region.

Keywords: grassland diversity - plant invasion - plant traits - soil seed bank - species composition - traffic

2016  Disrupting ectomycorrhizal symbiosis: Indirect effects of an annual invasive plant on growth and survival of beech (Fagus sylvatica) saplings — Ruckli R, Rusterholz H-P & Baur B — Perspectives in Plant Ecology, Evolution and Systematics 19: 12–20   doi> 10.1016/j.ppees.2016.01.005 

Understanding how invasive plants modify symbiotic interactions between ectomycorrhizal (EM) fungi and native host trees is a central goal in invasion biology. We examined the effect of the annual invasive plant Impatiens glandulifera on the EM association and performance of Fagus sylvatica saplings in a controlled field experiment at three sites in a deciduous forest in Switzerland. A total of 1188 one-year-old F. sylvatica saplings were planted either in plots invaded by I. glandulifera, in plots from which the invasive plant had been manually removed or in plots which were not yet colonized by the invasive plant. The 54 (3 × 18) plots were equally distributed over three sites. Saplings, including their full root systems were harvested after 3, 6 and 15 months. Exudates of the invasive plant were extracted from resin bags buried in the soil during the seedling, flowering and senescent stage of I. glandulifera. EM colonization on F. sylvatica saplings growing in invaded plot was 33% lower after 3 months and 66% lower after 15 months than saplings growing in plots from which I. glandulifera had been removed and in uninvaded plots. Survival and biomass of saplings were reduced by 16% and 30% after 15 months in plots invaded by I. glandulifera. Analysis of the internal transcribed spacer region of fungal rDNA (ITS) showed that the number of EM species was highly correlated with the number of EM morphotypes, indicating that the latter can be considered as a surrogate for EM species richness on roots of F. sylvatica saplings. EM morphotype richness on saplings was 32% lower after 15 months in invaded plots as compared to control plots. Chemical analysis revealed a high amount of naphthoquinones in plots with I. glandulifera suggesting that this putative allelochemical can be responsible for the reduction in both EM colonization and morphotype richness. Our findings demonstrate the negative impact of an annual invasive plant on the ectomycorrhizal symbiosis and performance of native F. sylvatica saplings.

Keywords: allelopathy - deciduous forest - disturbance - naphthoquinones - plant–soil feedback - resin bag

2016  Breeding system, shell size and age at sexual maturity affect sperm length in stylommatophoran gastropods — Schmera D, Pizá J, Reinartz E, Ursenbacher S & Baur B — BMC Evolutionary Biology 16: 89   doi> 10.1186/s12862-016-0661-9 

Sperm size and quality are key factors for fertilization success. There is increasing empirical evidence demonstrating that sperm form and function are influenced by selective pressures. Theoretical models predict that sperm competition could favour the evolution of longer sperm. In hermaphrodites, self-fertilizing species are expected to have shorter sperm than cross-fertilizing species, which use sperm stored from several mating partners for the fertilization of their eggs and thus are exposed to intense sperm competition. We tested this hypothesis by comparing original data on sperm length in 57 species of simultaneously hermaphroditic stylommatophoran gastropods from Europe and South America with respect to the species’ breeding system. We used 28S rRNA nuclear and COI mitochondrial sequence data to construct a molecular phylogeny. Phylogenetic generalized linear models were applied to examine the potential influence of morphological and life-history characters.
The best-fit model revealed that the breeding system and age at sexual maturity influence sperm length in gastropods. In general, species with predominant cross-fertilization had longer sperm than species with predominant self-fertilization or a mixed breeding system. Across species with shells (snails), sperm length also increased with shell size.
Our study provides evidence that sperm length in stylommatophoran gastropods is influenced by the risk of sperm competition, as well as by age at sexual maturity and shell size. This finding extends present knowledge of sperm evolution to a group of so far poorly studied simultaneous hermaphrodites.

Keywords: comparative approach - gastropods - phylogeny - sexual selection - sperm competition - sperm evolution

2016  King penguins in zoos: relating breeding success to husbandry practices — Schweizer S, Stoll P, von Houwald F & Baur B — Journal of Zoo and Aquarium Research 4: 91–98   doi> 10.19227/jzar.v4i2.163 
Artikel als pdf Datei herunterladen

As global climate change warms the Southern Ocean, wild king penguins (Aptenodytes patagonicus) may face drastic population declines in the future. Moreover, the captive breeding programme in Europe is currently unsustainable and it is thus imperative to determine what is required for the successful breeding of king penguins. A questionnaire was used to assess the husbandry practices and breeding success of 12 American and European zoos. Overall, a positive relationship was found between yearly egg productivity and density of king penguins held in enclosures in different zoos. All zoos examined showed male-biased adult sex ratios. Yearly egg productivity was negatively related to the deviation from an even sex ratio. Mean hatching success was greater in zoos performing outside walks with king penguins than in those that did not. Based on records over 40 years, the population of the sustainably breeding Basel Zoo in Switzerland was modelled using stage-based matrix models to gain an insight into its breeding success. Years of medium colony size (density of 0.25 to 0.38 individuals per m2) displayed a larger growth rate than years with high or low colony size, and years with equal sex ratios showed a higher growth rate than those with male-biased or female-biased sex ratios. The results suggest zoological institutions should focus on increasing density and strive toward equal sex ratios within king penguin populations to maximise breeding success. Where possible, adding outside walks should also be taken into consideration.

Keywords: Aptenodytes patagonicus - captive breeding - density - matrix model - sex ratio

2016  Recreational use of urban and suburban forests affects plant diversity in a Western Siberian city — Vakhlamova T, Rusterholz H-P, Kamkin V & Baur B — Urban Forestry & Urban Greening 17: 97–103   doi> 10.1016/j.ufug.2016.03.009 

The recreational use of urban forests is a highly valued service. However, strong recreational pressure may contribute to the loss of biodiversity in forests. This study assessed the frequency of visitors and their characteristics in 14 urban and 11 suburban forests in the rapidly expanding city of Pavlodar, Kazakhstan, in Western Siberia. Furthermore, the effects of recreation disturbance (trampling, damage to ground vegetation and damage to trees and shrubs) and other human-mediated disturbances (waste deposits, soil disturbance, etc.) on both the vegetation and plant characteristics of urban and suburban forests were quantified. In Pavlodar, urban forests are poorly managed, motivating the people to spend their sparetime in the more distant suburban forests. Urban and suburban forests did not differ in visitor frequency during the summer season (July–September). However, the two forest types differed in the age structure and group size of visitors as well as in the activities of visitors. Urban forests were more frequently visited by younger people for walking, sports, sitting and talking, and playing with children, while suburban forests were often visited by older people for picnicking, fishing and gathering mushrooms. In urban forests, total plant species richness was reduced by recreation disturbance. Urban forests also harboured a large proportion of alien plant species (0.42; in suburban forests 0.24). Neither recreation disturbance nor other human-mediated disturbance affected plant species richness in suburban forests, while both disturbance types enhanced the colonization success of alien species. Alterations in plant life forms can be considered as an indicator of changes in ecosystem function. In suburban forests, recreation disturbance caused a decline of geophytes and an increase of therophytes. We recommended various management actions to improve the recreation value of degraded urban forests in this Western Siberian city.

Keywords: human-mediated disturbance - plant diversity - plant life form - recreational use

2015  Changes in landscape composition of differently irrigated hay meadows in an arid mountain region — Riedener E, Melliger RL, Rusterholz H-P & Baur B — Applied Vegetation Science 18: 242–251   doi> 10.1111/avsc.12141 

Does the recent change from traditional to sprinkler irrigation result in alterations in the surrounding landscape of species-rich hay meadows in an arid Swiss mountain region? Are landscape composition and landscape heterogeneity important determinants of plant diversity in these meadows?

Southwestern Switzerland.

We surveyed vascular plant species in six traditionally and six sprinkler-irrigated hay meadows. Plant species were divided into grassland specialists and generalists. Individual landscape traits were assessed in circular areas with radii of 50 and 100 m around each meadow in a field survey. Aerial photographs were used to measure the percentage area covered by different habitat types in the present and prior to the installation of sprinklers at the same spatial scale as in the field surveys. The potential effects of irrigation technique and present-day landscape features on the plant diversity and species composition of hay meadows were examined with GLM and NMDS.

Landscape composition was more diverse for traditionally than for sprinkler-irrigated meadows, but did not differ prior to the installation of sprinklers. Total plant species richness and the number of specialists were negatively affected by the distance to the closest haystack. Generalists were positively influenced by a variety of different small-scale landscape traits in the surroundings, whereas the percentage area covered by woodland had a negative effect. Finally, hay meadows irrigated with sprinklers had an increased number of generalist plant species.

This study showed that the small-scale surroundings, and to some extent the type of irrigation, are important for the conservation of plant diversity of these meadows. Furthermore, the study suggests that the installation of sprinklers was associated with a homogenization of the landscape, which facilitates land use. Extensive management should be promoted by compensation payments for farmers to prevent intensification.

Keywords: generalists - grassland specialists - landscape traits - land-use change - semi-natural grassland - small-scale landscape - Valais (Switzerland) - water management

2015  Size-dependent shell growth and survival in natural populations of the rock-dwelling land snail Chondrina clienta — Schmera D, Baur A & Baur B — Canadian Journal of Zoology 93: 403–410   doi> 10.1139/cjz-2014-0307 

Rock-dwelling land snails, feeding on algae and lichens that grow on stone surfaces, may influence the structure and function of these ecosystems. Yet, little is known about the life history of rock-dwelling snails. We performed a 30-month mark–release–resight study in four populations of Chondrina clienta (Westerlund, 1883) inhabiting vertical walls of abandoned limestone quarries on the Baltic island of Öland, Sweden, to assess growth rate and survival of juvenile snails and determine age at maturity. We marked 800 individuals ranging in shell height from 1.4 to 4.9 mm, released them in their original habitat, and remeasured their shell height at intervals of 6 months. Shell growth of juvenile C. clienta was affected by the site (quarry wall) and the size of the individual, being highest in medium-sized snails. Shell growth occurred during both summer and winter. Annual apparent survival rates of C. clienta were size-dependent and ranged from 58.6% to 96.3%. Sexual maturity was reached at an age of 5 years, which is later than in most large snail species. Our study extends current knowledge on life history of land snails to a rarely studied group dwelling on rock surfaces.

Keywords: age at maturity - annual survival rate - Chondrina clienta - individual growth - life history - rock-dwelling land snail - terrestrial gastropod

2015  Seasonal effects on egg production and level of paternity in a natural population of a simultaneous hermaphrodite snail — Janssen R & Baur B — Ecology and Evolution 5: 2916–2928   doi> 10.1002/ece3.1560 

In a seasonal environment, the suitable time window for females to reproduce is restricted by both environmental conditions and the availability of males. In simultaneous hermaphrodites, which are female and male at the same time, selection on a trait that is solely beneficial for one sexual function cannot occur independently. Therefore, it is assumed that the optimal time window for reproduction is a compromise between the two sexual functions in simultaneous hermaphrodites, mediated by environmental conditions. We examined seasonal patterns of reproduction and the resulting paternity in a natural population of the simultaneously hermaphroditic land snail Arianta arbustorum. Adult and premature individuals (snails in a short protandric phase) were collected on four occasions over the entire active season. The snails were allowed to deposit eggs after which we assessed the level of paternity in their hatched offspring. Individuals mated throughout the reproductive season, whereas egg production – the major task of the female function – was restricted to the first half of the season. Snails collected in autumn were allowed to hibernate under laboratory conditions. As a result, we found that premature individuals began to mate late in the reproductive season, but did not start to produce eggs before emerging from hibernation. Our results demonstrate a temporal shift of reproductive activities; the egg production and oviposition occur mainly in the first half of the season, while sperm production and mating occur over the entire season. In subadult and adult snails, sperm obtained from several partners in the second part of the reproductive season are stored during hibernation for the fertilization of eggs in the successive years. These results extend our understanding of the influence of both natural and sexual selection on reproductive strategies in hermaphrodites.

Keywords: gastropod - hibernation - male function - multiple paternity - sperm storage

2015  DNA Quantity and Quality in Remnants of Traffic-Killed Specimens of an Endangered Longhorn Beetle: A Comparison of Different Methods — Rusterholz H-P, Ursenbacher S, Coray A, Weibel U & Baur B — Journal of Insect Science 15: 120   doi> 10.1093/jisesa/iev099 

The sampling of living insects should be avoided in highly endangered species when the sampling would further increase the risk of population extinction. Nonlethal sampling (wing clips or leg removals) can be an alternative to obtain DNA of individuals for population genetic studies. However, nonlethal sampling may not be possible for all insect species. We examined whether remnants of traffic-killed specimens of the endangered and protected flighless longhorn beetle Iberodorcadion fuliginator (L., 1758) can be used as a resource for population genetic analyses. Using insect fragments of traffic-killed specimens collected over 15_yr, we determined the most efficient DNA extraction method in relation to the state of the specimens (crushed, fragment, or intact), preservation (dried, airtight, or in ethanol), storage duration, and weight of the sample by assessing the quantity and quality of genomic DNA. A modified cetyltrimethyl ammonium bromide method provided the highest recovery rate of genomic DNA and the largest yield and highest quality of DNA. We further used traffic-killed specimens to evaluate two DNA amplification techniques (quantitative polymerase chain reaction [qPCR] and microsatellites). Both qPCR and microsatellites revealed successful DNA amplification in all degraded specimens or beetle fragments examined. However, relative qPCR concentration and peak height of microsatellites were affected by the state of specimen and storage duration but not by specimen weight. Our investigation demonstrates that degraded remnants of traffic-killed beetle specimens can serve as a source of high-quality genomic DNA, which allows to address conservation genetic issues.

Keywords: CTAB method - DNA quantity and quality - qPCR - microsatellite - Iberodorcadion fuliginator

2015  Wasserfälle: Ökologische und sozio-kulturelle Leistungen eines bedrohten Naturmonumentes — Rodewald R & Baur B (Red) — Bristol-Schriftenreihe Band 47. Haupt-Verlag, Bern, 246 Seiten

Dieses Buch stellt in einem interdisziplinären Ansatz die Bedeutung von Wasserfällen mit ihren ökologischen und soziokulturellen Qualitäten vor. Es zeigt, welche Pflanzen- und Tierarten im Spritzbereich von Wasserfällen vorkommen. Touristische und kunsthistorische Bedeutungen von Wasserfällen werden beschrieben und quantifiziert sowie Aspekte, welche die Gesundheit der Menschen fördern, skizziert. Zudem wird eine neue Methode zur Erfassung der landschaftsästhetischen Qualitäten vorgestellt. Abschließend werden Empfehlungen zur Beurteilung der Erhaltungswürdigkeit von Wasserfällen aufgeführt.
Das Buch präsentiert wertvolle Grundlagen zur Diskussion über die Zukunft der Wasserfälle in der Schweiz.

2014  Bodenschäden durch Freizeitaktivitäten im Wald: Regeneration durch Einzäunen — Rusterholz H-P & Baur B — Schweizerische Zeitschrift für Forstwesen 165: 2–9   doi> 10.3188/szf.2014.0002 

Urban forests are popular recreation areas. Recreational activities, particularly the use of picnic places and playing areas, can cause damages to soil and above-ground vegetation, which in turn negatively affect other forest functions. Forest management plans propose management tools for resolving these conflicts. So far, little is known concerning the restoration success of temporary fencing of heavily impacted forest areas in order to prevent any further recreational use. Here, we report the results of a field experiment designed to examine the effects of fencing and soil scarification upon regeneration of soil and above-ground vegetation in a highly impacted forest in Allschwil, Switzerland. We assessed different soil and vegetation parameters in plots with and without soil scarification in the fenced area in the year before the regeneration experiment was initiated and over the following seven years. In parallel, the same variables were recorded in an undisturbed area and in an area with ongoing recreational use. Our study showed successful regeneration of the formerly degenerated soil and ground vegetation within seven years. In addition, the scarification of the upper soil layer accelerated regeneration of some soil parameters but had no effect on ground vegetation. We conclude that temporary fencing is a useful tool for the restoration of forest soil and vegetation in areas heavily impacted by recreational activities.

2014  Invasion of an annual exotic plant into deciduous forests suppresses arbuscular mycorrhiza symbiosis and reduces performance of sycamore — Ruckli R, Rusterholz H-P & Baur B — Forest Ecology and Management 318: 285–293   doi> 10.1016/j.foreco.2014.01.015 

Invasive plants can disrupt associations between soil organisms and native trees which may result in altered ecosystem functions, both reduced biodiversity and timber production. We examined the effect of the invasive annual plant Impatiens glandulifera on the arbuscular mycorrhiza (AM) symbiosis and performance of Acer pseudoplatanus saplings at three different levels of disturbance in a controlled field experiment in a deciduous forest in Switzerland. A total of 1125 one-year-old A. pseudoplatanus saplings were planted either in plots invaded by I. glandulifera, in plots from which the invasive plant had been manually removed or in plots which were not yet colonised by the invasive plant. The 45 (3 × 15) plots were equally distributed over three forest areas which were differently affected by a wind throw 12 years prior to the experiment. Saplings including their full root systems were harvested after 3, 6 and 15 months. I. glandulifera reduced AM colonisation on A. pseudoplatanus saplings by 30–43%. Reduction in AM colonisation did not differ between harvesting time and was not affected by the level of forest disturbance. Saplings growing in invaded plots also showed a reduced root biomass and survival rate compared to saplings in the other plots. Increases in soil moisture, soil pH, available phosphorus and microbial activity found in plots invaded by I. glandulifera did not affect AM colonisation and performance of saplings. Our findings demonstrate that the spread of the invasive I. glandulifera in mixed deciduous forests negatively affects the symbiotic association between AM fungi and A. pseudoplatanus saplings and thus forest regeneration.

Keywords: Acer pseudoplatanus - disturbance - forest ecosystem - Impatiens glandulifera - plant–soil feedback - survival

2014  Developmental characteristics of the box-tree moth Cydalima perspectalis and its potential distribution in Europe — Nacambo S, Leuthardt FLG, Wan H, Li H, Haye T, Baur B, Weiss RM & Kenis M — Journal of Applied Entomology 138: 14–26   doi> 10.1111/jen.12078 

The box-tree moth Cydalima perspectalis (Walker) is an invasive pest causing severe damage to box trees (Buxus spp.). It is native to Japan, Korea and China, but established populations have been recorded in a number of locations across Europe since 2007 and the spread of the insect continues. The developmental investigations suggest that larvae overwinter mainly in their 3rd instar in Europe and that diapause is induced by a day length of about 13.5h. One and a half to 2months in the cold are necessary to terminate diapause. Threshold temperatures for development and number of degree-days to complete a generation are slightly different from those calculated in previous studies in Japan. A bioclimatic (CLIMEX (R)) model for C.perspectalis in Europe was developed, based on climate, ecological and developmental parameters from the literature and new field and laboratory studies on diapause termination, thermal requirements and phenology. The model was then validated with actual distribution records and phenology data. The current distribution and life history of C.perspectalis in Europe were consistent with the predicted distribution. The climate model suggests that C.perspectalis is likely to continue its spread across Europe, except for Northern Fenno-Scandinavia, Northern Scotland and high mountain regions. The northern distribution of C.perspectalis is expected to be limited by a number of degree-days above the temperature threshold insufficient to complete a generation, whereas its southern range is limited by the absence of a cold period necessary to resume diapause. The model predicts relatively high Ecoclimatic Indices throughout most of Europe, suggesting that the insect has the potential of becoming a pest in most of its predicted range. However, damage is likely to be higher in Southern and Central Europe where the moth is able to complete at least two generations per year.

Keywords: bioclimatic model - CLIMEX - Cydalima perspectalis - diapause - invasive species - temperature requirements

2014  Land-use abandonment owing to irrigation cessation affects the biodiversity of hay meadows in an arid mountain region — Riedener E, Rusterholz H-P & Baur B — Agriculture, Ecosystems & Environment 185: 144–152   doi> 10.1016/j.agee.2013.12.023 

In arid regions, irrigation is required to secure agricultural production including the production of hay. The Valais, a dry inner alpine valley of Switzerland, has a long tradition of meadow irrigation. However, in the 20th century irrigation was stopped on marginal, poorly accessible areas usually accompanied by the entire abandonment of these meadows. The aim of this study was to examine the consequences of land-use abandonment resulting from the cessation of irrigation for the biodiversity of species-rich hay meadows in the Valais. We compared soil characteristics and species richness and composition, habitat specificity and functional traits of plants and gastropods of three serial stages of succession (each five hay meadows, early abandoned meadows and young forests). Soil moisture was lower in young forests than in the other two stages. Soil nitrogen content decreased following abandonment, which was due to the cessation of fertilization. The three successional stages did not differ in plant species richness but harboured distinct plant communities. Gastropod richness increased with progressive succession and species composition of hay meadows differed from those of the two other stages. The proportion of grassland (plants) and open-land (gastropods) species decreased following abandonment. Furthermore, meadow abandonment led to an increase in the height of non-woody plant species, a later start of seed shedding, a change in the type of plant reproduction and an increase in the shell size of gastropods. In conclusion, this study showed that extensive land-use, which is strongly linked to irrigation, is required for the characteristic species-rich hay meadows of this arid mountain region.

Keywords: land-use change - grassland succession - plants - gastropods - soil characteristics - Valais (Switzerland)

2014  Terrestrial gastropod diversity in an alpine region: Disentangling effects of elevation, area, geometric constraints, habitat type and land-use intensity — Baur B, Meier T, Baur A & Schmera D — Ecography 37: 390–401   doi> 10.1111/j.1600-0587.2013.00312.x 

Elevational gradients have proven to be useful to examine key factors shaping species diversity patterns. This study examines the effects of elevation, area, geometric constraints, habitat type, environmental factors and land-use intensity on terrestrial gastropod diversity patterns in Val Müstair, an alpine region influenced by different types of agricultural land use in the eastern Alps, Switzerland. Gastropods were sampled using a standardized method in 180 sites spanning an elevational range from 1215 to 2770 m and covering 11 different habitat types. A total of 11 102 specimens representing 70 species were recorded. Observed species richness, statistically estimated true richness (Chao) and geographically interpolated observed richness were used as measures of local species richness. The comparison of three alternative models (environmental, geometric constraints and gastropod abundance models) revealed that the environmental model explained most of the variation in all measures of local diversity. The best model combining the predictors of all three models showed that elevation, soil pH and habitat type affected all measures of local species richness. Similar analyses conducted at the level of 150-m elevational bands showed that elevation was again the best predictor of species richness, while the area of the elevational band did not have any influence. However, in one out of the two measures of band species richness, the best model indicated that geometric constraints may also contribute to the observed pattern. At both spatial scales, all measures of species richness decreased with increasing elevation. An analysis of species-specific life-history traits showed that adult shell size of land snails decreased with increasing elevation. Most species with large shells were confined to lower elevations. The results indicate that environmental factors might be most important in shaping the observed patterns.

2014  Vielfalt der Landschnecken in der Val Müstair — Baur B, Meier T, Schmera D, Baur M & Baur A — Nationalpark-Forschung in der Schweiz 102, Haupt Verlag, Bern, 212 Seiten

Landschnecken spielen als Zersetzer von totem Pflanzenmaterial eine wichtige Rolle im Stoffkreislauf der Natur. Sie werden aber kaum wahrgenommen, weil viele von ihnen ein Gehäuse von nur wenigen Millimetern Grösse haben. Die Autorinnen und Autoren untersuchten anhand umfangreicher Feldaufnahmen die Vielfalt der Landschnecken in den unterschiedlichsten Lebensräumen der Biosfera Val Müstair. Als Ergebnis wird nicht nur eine Zustandsbeschreibung präsentiert, sondern es werden auch natürliche Faktoren und menschliche Einflüsse vorgestellt, welche die Vielfalt und Artzusammensetzung dieser Tiergruppe beeinflussen. Schnecken gelten als ausgezeichnete Zeigerorganismen und erlauben Rückschlüsse auf den Zustand der Lebensräume in der Biosfera Val Müstair.

2014  Wissen schaffen - 100 Jahre Forschung im Schweizerischen Nationalpark — Baur B & Scheurer T (Red) — Nationalpark-Forschung in der Schweiz 100, Haupt Verlag, Bern, 391 Seiten

100 Jahre Schweizerischer Nationalpark. Die Schweizerische Akademie der Naturwissenschaften war massgeblich an der Gründung des Schweizerischen Nationalparks 1914 beteiligt. Unter Ausschluss des Menschen sollte hier ein großartiges Freiluftlaboratorium zum Studium der ungestörten Naturentwicklung entstehen. Was wissen wir heute über die Entwicklung des Parks? Welche Erkenntnisse hat die Wissenschaft hervorgebracht? Welche Lehren können aus dem Experiment Nationalpark gezogen werden? «Wissen schaffen» zeigt die Vielfalt der Forschung seit 1914 und fasst herausragende Ergebnisse zusammen.

2014  Random mating with respect to mating status in the simultaneously hermaphroditic land snail Arianta arbustorum — Häussler EM, Schmera D, Baur A & Baur B — Invertebrate Reproduction and Development: 58: 115–123   doi> 10.1080/07924259.2013.855267 

In promiscuous species with sperm storage, males are expected to show a preference for mating with virgin and young females to reduce the risk of sperm competition. In the simultaneous hermaphrodite land snail Arianta arbustorum, sperm production precedes egg production by 2–4 weeks, resulting in a short period of protandric hermaphroditism before shell growth is completed. In natural populations, copulating pairs involving individuals which have not yet completed shell growth (virgins) have been observed. We ran a series of mate-choice experiments to examine whether virgin and nonvirgin (experienced) individuals of A. arbustorum discriminate between virgin and nonvirgin mating partners. We also assessed the number of sperm delivered to partners with different mating status. Neither virgin nor nonvirgin snails showed any preference for mating with a virgin partner. In all test situations mating was random and the number of sperm delivered was not adjusted to the mating status of the partner. Mating success was mainly determined by the activity of the individual. The random mating pattern does not imply random fertilization of eggs because the presence of a sperm-digesting organ and the morphology of the sperm storage organ allow a selective storage and use of sperm in A. arbustorum.

Keywords: mate choice - mate recognition - mating behavior - preference - sexual selection

2014  Inhibitory potential of naphthoquinones leached from leaves and exuded from roots of the invasive plant Impatiens glandulifera — Ruckli R, Hesse K, Glauser G, Rusterholz H-P & Baur B — Journal of Chemical Ecology 40: 371–378   doi> 10.1007/s10886-014-0421-5 

Exploring the effects of allelopathic plant chemicals on the growth of native vegetation is essential to understand their ecological roles and importance in exotic plant invasion. Naphthoquinones have been identified as potential growth inhibitors produced by Impatiens glandulifera, an exotic annual plant that recently invaded temperate forests in Europe. However, naphthoquinone release and inhibitory potential have not been examined. We quantified the naphthoquinone content in cotyledons, leaves, stems, and roots from plants of different ages of both the invasive I. glandulifera and native Impatiens noli-tangere as well as in soil extracts and rainwater rinsed from leaves of either plant species by using ultra-high pressure liquid chromatography-mass spectrometry (UHPLC-MS). We identified the compound 2-methoxy-1,4-naphthoquinone (2-MNQ) exclusively in plant organs of I. glandulifera, in resin bags buried into the soil of patches invaded by I. glandulifera, and in rainwater rinsed from its leaves. This indicates that 2-MNQ is released from the roots of I. glandulifera and leached from its leaves by rain. Specific bioassays using aqueous shoot and root extracts revealed a strong inhibitory effect on the germination of two native forest herbs and on the mycelium growth of three ectomycorrhiza fungi. These findings suggest that the release of 2-MNQ may contribute to the invasion success of I. glandulifera and support the novel weapons hypothesis.

Keywords: Impatiens glandulifera - chemical defence - 2-methoxy-1,4-naphthoquinone - ectomycorrhiza - invasion

2014  Do different irrigation techniques affect the small-scale patterns of plant diversity and soil characteristics in mountain hay meadows? — Melliger RL, Riedener E, Rusterholz H-P & Baur B — Plant Ecology 215: 1037–1046   doi> 10.1007/s11258-014-0360-9 

Traditional management practices are suggested to maintain species-rich grasslands. In the Valais, an arid region of Switzerland, hay meadows are traditionally irrigated using open water channels. However, in the past decades this irrigation technique has been increasingly replaced by sprinkler irrigation, which is assumed to result in a more homogeneous water distribution than open water channels. This study examined whether the change in irrigation technique affected the small-scale distribution of plants and soil characteristics in hay meadows in the Valais. Three plots consisting of 13 subplots of increasing size (0.1 × 0.1 to 6.4 × 6.4 m) were installed in six traditionally and six sprinkler-irrigated meadows. In all subplots, plant species richness and soil characteristics [moisture, pH, total organic nitrogen, organic matter content (SOM), total and plant available phosphorus] were recorded. The type of irrigation technique did not affect the shape of the plant species–area relationship. In none of the meadows did the species area–curves reach the asymptote within the range of plot sizes examined. Mantel r statistics showed that spatial autocorrelation in the soil characteristics examined was low and their small-scale distributions were not influenced by the irrigation technique except for soil pH and SOM. Our results indicate a pronounced small-scale heterogeneity in the distribution of plant species and soil characteristics for both types of irrigation technique. This can partly be explained by the fact that sprinklers distribute the water less homogeneously than commonly assumed. As applied in the Valais, sprinkler irrigation does not reduce the spatial heterogeneity and hence biodiversity of hay meadows.

Keywords: semi-natural grassland - water management - land use change - species–area relationship - spatial autocorrelation - Valais (Switzerland)

2014  Dispersal-limited species – A challenge for ecological restoration — Baur B — Basic and Applied Ecology 15: 559–564   doi> 10.1016/j.baae.2014.06.004 

In recent years, increasing efforts have been directed to the restoration of natural communities affected by human activities. However, restoration success is often reduced because of the lack of dispersal-limited species in the restored site. Numerous rare species are dispersal-limited, having low probabilities to re-colonize restored sites and to establish viable populations. A high species richness enhances the ability of ecosystems to maintain multiple functions. It has been shown that in highly diverse ecosystems such as alpine meadows, tropical forests and coral reefs, the most distinct combinations of functions are supported predominantly by rare species. Thus, more emphasis should be given to support rare species in restoration actions. I suggest that well-known techniques for increasing plant diversity in restoration projects should be complemented with techniques to re-introduce dispersal-limited animals. Re-establishing ecological connectivity might be of benefit for certain species in the long term. However, for the majority of dispersal-limited animal species, translocations of founder individuals might be the only tool to re-establish populations in restored sites.

Keywords: biodiversity - dispersal - ecosystem function - extinction - rare species - translocation

2014  Parasitic mites influence intra- and interpopulational variation in sperm length in a simultaneous hermaphrodite land snail (Gastropoda: Helicidae) — Häussler EM, Schmera D & Baur B — Biological Journal of the Linnean Society 113: 1036–1046   doi> 10.1111/bij.12377 

Sperm morphology can be highly variable among species, but less is known about patterns of population differentiation within species. Sperm morphology is under strong sexual selection, may evolve rapidly, and often co-varies with other reproductive traits that differ between populations. We investigated variation in sperm morphology in the simultaneous hermaphrodite land snail Arianta arbustorum in relation to parasitic mite infection. Variation in total sperm length and sperm head length was assessed in 23 populations sampled across the distributional range of the species in Central and Northern Europe. We found a pronounced variation in total sperm length among the populations studied, with a difference of 11.0% of total sperm length between the shortest and longest population means. Differences among populations explained 62.9% of the variance in total sperm length, differences among individual snails within population 23.4% and differences within individual snail 13.7%. Mantel tests showed that interpopulation differences in total sperm length increased significantly with geographical distance between populations. A minimal adequate model revealed that parasitic infection had a positive effect and longitude a negative effect on total sperm length. Thus, independent of the population examined, mite-infected individuals of A._arbustorum produced larger sperm than uninfected snails and total sperm length decreased from west to east. Sperm head length also varied among populations, but it was not influenced by any of the factors examined. In a subsample of 12 populations restricted to the mountains of Switzerland (elevational range 440–2485_m_a.s.l.), total sperm length decreased with increasing elevation. Our results suggest that selection pressures acting among populations may differ from those acting within. Stabilizing selection might be a possible mechanism for producing the reduced variation observed in sperm length within a population.

Keywords: Arianta arbustorum - elevation - geographical variation - parasite - sperm length

2014  Gastropod communities in alpine grasslands are characterized by high beta diversity — Schmera D & Baur B — Community Ecology 15: 246–255   doi> 10.1556/ComEc.15.2014.2.13 

Alpine grasslands harbour species-rich communities of plants and invertebrates. We examined how environmental variables and anthropogenic impact shape species richness and community structure of terrestrial gastropods in alpine grasslands in the Val Müstair (Eastern Alps, Switzerland). Gastropods were sampled using a standardised method at 76 sites spanning an elevation range from 1430 m to 2770 m. A total of 4763 specimens representing 52 species were recorded. Correspondence analysis based on presence/absence data revealed that the grassland gastropod community was structured in a complex way with elevation, wetness, grazing intensity and inclination of the sites as key factors, while abundance-based analysis identified the importance of the elevation and wetness of sites. Generalized linear model showed that species richness decreased with increasing elevation and increased with increasing soil pH. The grassland gastropod communities were characterized by a high beta diversity, as indicated by the SDR-simplex analysis. Species-specific traits of gastropods showed sensitivity to the environmental characters of the sites, as shown by a fourth-corner analysis.

Keywords: community assembly - grassland management - grazing intensity - SDR-simplex analysis - species richness - species traits

2014  Effects of the annual invasive plant Impatiens glandulifera on the Collembola and Acari communities in a deciduous forest — Rusterholz H-P, Salamon J-A, Ruckli R & Baur B — Pedobiologia 57: 285–291   doi> 10.1016/j.pedobi.2014.07.001 

Invasive plants can disturb interactions between soil organisms and native plants and thereby alter ecosystem functions and/or reduce local biodiversity. Collembola and Acari are the most abundant microarthropods in the leaf litter and soil playing a key role in the decomposition of organic material and nutrient cycling. We designed a field experiment to examine the potential effects of the annual invasive plant Impatiens glandulifera on species diversity, abundance and community composition of Collembola and Acari in leaf litter and soil in a deciduous forest in Switzerland. Leaf litter and soil samples were obtained from plots invaded by I. glandulifera since 6 years, from plots in which the invasive plant had been removed for 4 years and from plots which were not yet colonized by the invasive plant. The 45 leaf litter and soil samples were equally distributed over three forest areas, which were differently affected by a wind throw 12 years prior to sampling representing a natural gradient of disturbance. Collembola species richness and abundance in the leaf litter and soil samples were not affected by the presence of the invasive plant. However, the species composition of Collembola was altered in plots with I. glandulifera. The abundance of leaf-litter dwelling Acari was increased in invaded plots compared to the two other plot types. Furthermore, the presence of the invasive plant shifted the composition of Acari individuals belonging to different groups. Our field experiment demonstrates that an annual invasive plant can affect microarthropods which are important for nutrient cycling in various ecosystems.

Keywords: alien plant - beech forests - microarthropods - soil characteristics

2014  Changes in plant diversity along an urban–rural gradient in an expanding city in Kazakhstan, Western Siberia — Vakhlamova T, Rusterholz H-P, Kanibolotskay Y & Baur B — Landscape and Urban Planning 132: 111–120   doi> 10.1016/j.landurbplan.2014.08.014 

Plant communities respond sensitively to urban expansion and therefore serve as indicators for human land use. An urban–rural gradient approach was used to examine changes in plant species composition and abundance related to human-altered habitats in the Western Siberian city of Pavlodar (Kazakhstan). This region is characterized by harsh continental environmental conditions and recent anthropogenic degradation of the original steppe grasslands as a result of enforced land-use changes (Virgin Land Campaign) and rapidly expanding urbanization. Plant diversity and abundance as well as the percentage of alien species were recorded in plots on four 20-km long transect lines running from the city centre to the rural surroundings. Various habitat and landscape characteristics were assessed along the transect lines to describe the urban–rural gradient. Based on the results of a principal component analysis considering these landscape characteristics the variable “distance to the city centre” was used as proxy for the urban–rural gradient. Plant diversity increased with increasing distance to the city centre and was also influenced by the type of land use (ornamentally managed, agricultural or unmanaged land) and the percentage cover of built-up area within a 500 m radius. The percentage of alien species decreased from 45% in the city centre to 23% in the rural surroundings. The percentage of species belonging to different plant life forms and to different evolutionary strategies were affected by different landscape characteristics. The study showed that the combined effects of expanding urbanization and agricultural land-use changes altered the plant species composition.

Keywords: alien species - plant life form - plant evolutionary strategy - steppe grassland - urbanization

2013  Oviposition preference and larval development of the invasive moth Cydalima perspectalis on five European box-tree varieties — Leuthardt FLG & Baur B — Journal of Applied Entomology 137: 437–444   doi> 10.1111/jen.12013 

The box-tree pyralid Cydalima perspectalis (Walker 1859) (Lepidoptera: Pyralidae), native to Eastern Asia, is a newly introduced species causing severe damage to box-trees (Buxus sp.) in private and public gardens as well as in semi-natural box-tree forests in Central Europe. It is so far not known whether different box-tree subspecies (or varieties) are similarly affected by this invasive moth. In a choice experiment offering branches of five different box-tree varieties as oviposition sites, we found a preference of female moths for laying their egg clusters on the variety ‘Rotundifolia’, while other varieties were less frequently considered. The preference for ‘Rotundifolia’, the variety with the largest leaves in the tests, remained when intervariety differences in foliar area (mean leaf size × number of leaves) were taken into account. Feeding larvae on leaves of either of the five box-tree varieties revealed a significant effect of the seasonal generation of C. perspectalis on the growth rate of individuals but no influence of the box-tree variety. Larvae from the spring generation show the highest growth rate, those from the summer generation a moderate and those from the autumn generation the lowest growth rate. The moths used in the experiments may belong to the 10th to 12th generation present in Europe. The time elapsed since their introduction may be too short for an optimal adaptation to the partly novel diet encountered by the invasive moth.

Keywords: Buxus - Cydalima perspectalis - invasive species - larval development - oviposition preference

2013  Invasion of Impatiens glandulifera affects terrestrial gastropods by altering microclimate — Ruckli R, Rusterholz H-P & Baur B — Acta Oecologica 47: 16–23   doi> 10.1016/j.actao.2012.10.011 

Invasive species can have far-reaching impacts on ecosystems. Invasive plants may be able to change habitat structure and quality. We conducted a field experiment to examine whether the invasive plant Impatiens glandulifera affects native terrestrial gastropods. We also evaluated whether the invasive plant alters forest soil characteristics and microclimate which in turn may influence gastropod abundance. We sampled gastropods in plots installed in patches of I. glandulifera, in plots in which I. glandulifera was regularly removed by hand, and in control plots which were not yet colonized by the invasive plant. The three types of plots were equally distributed over three mixed deciduous forest areas that were slightly, moderately or heavily affected by a wind throw 11 years ago. A total of 33 gastropod species were recorded. Gastropod species richness was not affected by delayed effects of the wind throw, but it was significantly higher in invaded plots than in uninvaded plots. Similarly, gastropod abundance was higher in invaded plots than in the two types of control plots. Canonical correspondence analysis revealed marginally significant shifts of gastropod communities between the three types of plots and indicated that soil moisture, presence of I. glandulifera and cover of woody debris affected gastropod species composition. Field measurements showed that soil moisture was higher and daily soil temperature was more damped in patches of I. glandulifera than in the native ground vegetation. The changed microclimatic conditions may favour certain gastropod species. In particular, ubiquitous species and species with a high inundation tolerance increased in abundance in plots invaded by I. glandulifera. Our field experiment demonstrated that an invasive plant can indirectly affect native organisms by changing soil characteristics and microclimate.

Keywords: biodiversity - deciduous forests - ecosystem change - exotic plant - disturbance - gastropod community

2013  Effects of different irrigation systems on the biodiversity of species-rich hay meadows — Riedener E, Rusterholz H-P & Baur B — Agriculture, Ecosystems & Environment 164: 62–69   doi> 10.1016/j.agee.2012.09.020 

The maintenance of traditional management practices is essential for the conservation of the biodiversity of semi-natural grasslands including species-rich hay meadows. In the canton Valais (Switzerland), hay meadows are traditionally irrigated using open water channels. However, since the 1980s, this labour intensive irrigation technique has been increasingly replaced by sprinkler irrigation. This study examined whether the different irrigation techniques (traditional vs. sprinkler) influence the local biodiversity of species-rich hay meadows. In particular, the diversity and composition of plant and gastropod species of eight traditionally irrigated meadows were compared with those of eight sprinkler-irrigated meadows. It was also assessed whether the species of either meadow type differed in functional traits. A high plant species richness was found in the meadows investigated. The study showed that the diversity and composition of plant and gastropod species of hay meadows were not affected by the change in irrigation technique 8–18 years ago. However, a lower grass/forb-ratio was observed in traditionally than in sprinkler-irrigated meadows. Furthermore, irrigation technique affected the leaf distribution and the onset of seed shedding in plants. Thus, the change in the irrigation technique altered only some aspects of biodiversity. Therefore, irrigation system alone does not represent the major factor affecting the biodiversity of hay meadows investigated.

Keywords: semi-natural grassland - water management - land-use change - functional traits - plants - gastropods

2013  Composition of alkaloids in different box tree varieties and their uptake by the box tree moth Cydalima perspectalis — Leuthardt FLG, Glauser G & Baur B — Chemoecology 23: 203–212   doi> 10.1007/s00049-013-0134-1 

Larvae of the moth Cydalima perspectalis are specialized on box trees (Buxus spp.). Native to eastern Asia, the moth has been introduced to Europe in 2007 and is nowadays causing severe damage to box trees in private and public gardens, as well as in semi-natural box tree forests. Box trees contain highly toxic triterpenoid alkaloids which may be sequestered by specialized herbivores such as C. perspectalis. We determined the alkaloid composition in leaves of the five most common box tree varieties in Europe belonging to two Buxus species using liquid chromatography–mass spectrometry (LC–MS) metabolite profiling. We also examined whether larvae and moths of C. perspectalis accumulate alkaloids from the different box tree varieties. The differences in alkaloid composition observed between the box tree species Buxus sempervirens and Buxus microphylla were mirrored in the tissue of C. perspectalis larvae fed on either of the different box tree species, indicating uptake of alkaloids. The larvae stored large amounts of dibasic alkaloids in their body, while monobasic alkaloids were metabolized and/or excreted. Newly emerged adult moths contained no traces of alkaloids.

Keywords: Buxus - Lepidoptera - chemical defence - triterpenoid alkaloids - plant–insect interactions - UHPLC–QTOFMS

2013  Die Ringelnatter im Schweizer Landwirtschaftsgebiet – Einfluss unterschiedlich genutzter Landschaften auf die genetische Populationsstruktur — Meister B & Baur B — Bristol-Schriftenreihe Band 37, Haupt Verlag, Bern, 112 Seiten

Der Bestand der Barrenringelnatter ist in der Schweiz im 20. Jahrhundert stark zurückgegangen, insbesondere im Mittelland. Deshalb wird die Barrenringelnatter auf der Roten Liste der gefährdeten Arten als «verletzlich» geführt. Als Folge der veränderten Landnutzung und der Entwässerung von Feuchtgebieten hat die Fläche ihrer Lebensräume abgenommen.
Zudem führt die zunehmende Zersiedelung zu einer Fragmentierung der Lebensräume. Fehlender Genfluss zwischen Teilpopulationen kann zur genetischen Verarmung führen, die ein erhöhtes Aussterberisiko für die betroffenen Populationen bedeutet.
Im vorliegenden Band wird die genetische Populationsstruktur der Ringelnatter mithilfe molekulargenetischer Methoden in drei Gebieten untersucht: in einem intensiv genutzten Landwirtschaftsgebiet, in einer ehemaligen Auenlandschaft und in einem ländlichen Tal in den Berner Alpen. Die Ergebnisse werden auf einer lokalen und einer regionalen Ebene diskutiert. Der Einfluss des Paarungsmusters der Schlangen auf die Populationsstruktur wird ebenfalls behandelt. Zudem wird eine mögliche genetische Vermischung der einheimischen Ringelnattern mit eingeführten, standortfremden Schlangen untersucht. Aufgrund der Ergebnisse werden allgemeine Schlussfolgerungen sowie Empfehlungen für den praktischen Naturschutz abgeleitet

2013  Habitat quality and geometry affect patch occupancy of two Orthopteran species — Pasinelli G, Meichty-Stier K, Birrer SB & Duss M — PLOS ONE 8: e65850   doi> 10.1371/journal.pone.0065850 

Impacts of habitat loss and fragmentation on distribution and population size of many taxa are well established. In contrast, less is known about the role of within-patch habitat quality for the spatial dynamics of species, even though within-patch habitat quality may substantially influence the dynamics of population networks. We studied occurrence patterns of two Orthopteran species in relation to size, isolation and quality of habitat patches in an intensively managed agricultural landscape (16.65 km²) in the Swiss lowland. Occurrence of field crickets (Gryllus campestris) was positively related to patch size and negatively to the distance to the nearest occupied patch, two measures of patch geometry. Moreover, field crickets were more likely to occur in extensively managed meadows, meadows used at low intensity and meadows dominated by Poa pratensis, three measures of patch quality. Occurrence of the large gold grasshopper (Chrysochraon dispar) was negatively related to two measures of patch geometry, distance to the nearest occupied patch and perimeter index (ratio of perimeter length to patch area). Further, large gold grasshoppers were more likely to occupy patches close to water and patches with vegetation left uncut over winter, two measures of patch quality. Finally, examination of patch occupancy dynamics of field crickets revealed that patches colonized in 2009 and patches occupied in both 2005 and 2009 were larger, better connected and of other quality than patches remaining unoccupied and patches from which the species disappeared. The strong relationships between Orthopteran occurrence and aspects of patch geometry found in this study support the "area-and-isolation paradigm". Additionally, our study reveals the importance of patch quality for occurrence patterns of both species, and for patch occupancy dynamics in the field cricket. An increased understanding of patch occupancy patterns may be gained if inference is based on variables related to both habitat geometry and quality.

2013  Heritability of sperm length and shell size in the land snail Arianta arbustorum — Minoretti N, Stoll P & Baur B — Journal of Molluscan Studies 79: 218–224   doi> 10.1093/mollus/eyt012 

Sperm length varies considerably, both between and within species, but the evolutionary implications of this variation are poorly understood. Sexual selection on sperm length requires a significant additive genetic variance, but few studies have actually measured this. Stylommatophoran gastropods have extraordinarily long sperm. However, the extent of intraspecific variation has rarely been examined. Here we present the first estimates of heritability of sperm length in the land snail Arianta arbustorum using two complementary approaches (one-parent–offspring regression and full-sibling split design). We also examined whether sperm length is influenced by the shell size of the snail and estimated heritability of shell size. Sperm delivered by the same individuals in 2–4 matings over two reproductive seasons did not differ in length, indicating a high repeatability of this trait. Offspring of 10 families were kept at three temperatures (11, 15 and 20°C) to examine the influence of different environmental conditions on sperm length and adult shell breadth. Independent of shell breadth, sperm length was affected by temperature but not by family of origin (the variance component associated with family was not significantly different from zero), while adult shell breadth was influenced by temperature and family of origin. Higher temperatures resulted in shorter sperm, but larger shells. The heritability of sperm length derived from the two different approaches (one-parent–offspring regression: h2 ± SE = 0.52 ± 0.55; full-sibling split design: H2 ± SE = _0.19 ± 0.28) suggests relatively little genetic variation in this trait in the studied population. In contrast, the heritability of adult shell breadth indicates a strong genetic effect (mother–offspring regression, h2 ± SE = 0.90 ± 0.33). The heritability (h2 ± SE) of adult shell breadth obtained from the father–offspring regression was 0.18 ± 0.42, i.e. five times smaller than that of the mother–offspring regression, suggesting a maternal effect on shell size.

2013  Snails keep the pace: shift in upper elevational limit on mountain slopes as a response to climate warming — Baur B & Baur A — Canadian Journal of Zoology 91: 596–599   doi> 10.1139/cjz-2013-0036 

Predicted biological responses to climate warming are changes in phenology and poleward shifts or upslope displacements of the distribution of species. We investigated changes in the upper elevational limit of the land snail Arianta arbustorum (L., 1758) by repeating historical records from 1916 to 1917 on nine mountain slopes in the Swiss National Park in 2011–2012. We found that the upper elevational limit for snail populations has risen, on average, by 164 m in 95 years, accompanying a 1.6 °C rise in mean annual temperature in the investigation area. The higher temperature results in an upslope shift of the vegetation and in a prolonged activity period of the snails. Upslope extension of snail distribution was not influenced by the inclination of the slope, but it was larger on south-exposed slopes (mean: 233 m) than on north to northeast exposed slopes (122 m). On some slopes we found that the snails have already reached natural barriers (vertical rock walls with no soil), preventing any farther upward dispersal. To our knowledge, this is the first evidence for an invertebrate species with low dispersal capacity ascending to higher elevations in a mountain area in response to climate warming.

2013  The 50 most important questions relating to the maintenance and restoration of an ecological continuum in the European Alps — Walzer C, Kowalczyk C, Alexander JM, Baur B, Bogliani G, Brun J-J, Füreder L, Guth M-O, Haller R, Holderegger R, Kohler Y, Kueffer C, Righetti A, Spaar R, Sutherland WJ, Ullrich-Schneider A, Vanpeene-Bruhier SN & Scheurer T — PLOS ONE 8: e153139   doi> 10.1371/journal.pone.0053139 

The European Alps harbour a unique and species-rich biodiversity, which is increasingly impacted by habitat fragmentation through land-use changes, urbanization and expanding transport infrastructure. In this study, we identified the 50 most important questions relating to the maintenance and restoration of an ecological continuum – the connectedness of ecological processes across many scales including trophic relationship and disturbance processes and hydro-ecological flows in the European Alps. We initiated and implemented a trans-national priority setting exercise, inviting 48 institutions including researchers, conservation practitioners, NGOs, policymakers and administrators from the Alpine region. The exercise was composed of an initial call for pertinent questions, a first online evaluation of the received questions and a final discussion and selection process during a joint workshop. The participating institutions generated 484 initial questions, which were condensed to the 50 most important questions by 16 workshop participants. We suggest new approaches in tackling the issue of an ecological continuum in the Alps by analysing and classifying the characteristics of the resulting questions in a non-prioritized form as well as in a visual conceptualisation of the inter-dependencies among these questions. This priority setting exercise will support research and funding institutions in channelling their capacities and resources towards questions that need to be urgently addressed in order to facilitate significant progress in biodiversity conservation in the European Alps.

2013  An immunolabelling technique to track sperm from different mates in the female reproductive organs of terrestrial gastropods — Kupfernagel S, Beier K, Janssen R, Rusterholz H-P, Baur A & Baur B — Malacologia 56: 253–266

The mechanisms of sperm transfer, storage, utilization and digestion are crucial for understanding processes of postcopulatory sexual selection. Previous studies analysing postcopulatory processes have generally focused only on the ultimate outcome of the interactions between male and female sexual selection (paternity patterns). For a mechanistic understanding of the fate of received sperm and the involved patterns of postcopulatory sexual selection new techniques are required. Here we present an improved immunolabelling technique to track the fate of 5-bromo-2'-deoxyuridine (BrdU)-labelled sperm in the female reproductive organs of gastropods. The technique was tested in individuals of the simultaneously hermaphroditic land snail Arianta arbustorum (Linnaeus, 1758). We determined the percentage of labelled sperm in spermatophores delivered and assessed the reliability of detecting labelled sperm in the spermatheca (sperm storage organ) and bursa copulatrix (sperm digestion organ) of the recipients. In our tests, the proportion of sperm labelled among the sperm produced by an individual averaged 99.3%. Furthermore, labelled sperm could be consistently visualized in both the sperm storage and sperm digestion organ of all recipients examined. Combined with a traditional sperm staining technique, we showed that the BrdU-labelling technique allows us to distinguish between sperm from two males in the female reproductive tract of double-mated snails. In a controlled growth experiment, we found that repeated BrdU-application slightly retarded shell growth of juvenile snails, but did not influence their adult size, survival, number of sperm delivered and mating frequency. The technique presented could be adjusted to other gastropod species providing insight into mechanisms of sperm competition and cryptic female choice.

Keywords: Arianta arbustorum - female reproductive organs - Gastropoda - immunolabelling - postcopulatory sexual selection - spermatheca - sperm digesting organ - sperm storage

2012  Separate introductions but lack of genetic variability in the invasive clam Corbicula spp. in Swiss lakes — Schmidlin S, Schmera D, Ursenbacher S & Baur B — Aquatic Invasions 7: 73–80   doi> 10.3391/ai.2012.7.1.008 
Artikel als pdf Datei herunterladen

This study documents the spread of the invasive clam Corbicula spp. in Switzerland since its first record in the River Rhine in 1995. Clams were newly recorded in several Swiss lowland lakes whose interconnecting rivers have not yet been colonized. We present evidence for separate introductions of an identical haplotype of Corbicula fluminea into five lakes in Switzerland in the years 2003–2010 based on the mitochondrial DNA-sequence of the COI in specimens sampled. This suggests passive dispersal of the clam by human activities and/or waterfowl. All but one of the 72 genetically analysed individuals were assigned to a single haplotype FW5 and to the species name C. fluminea. Recent records of specimens, which were not genetically analysed, displayed all the shell morphology of C. fluminea, confirming the dominance of this clam in Swiss rivers and lakes.

Keywords: alien species - DNA sequencing - COI - invasive species - range expansion - Corbicula - Switzerland

2012  Alien molluscs affect the composition and diversity of native macroinvertebrates in a sandy flat of Lake Neuchâtel, Switzerland — Schmidlin S, Schmera D & Baur B — Hydrobiologia 679: 233–249   doi> 10.1007/s10750-011-0889-8 

The spread of alien molluscs is a serious threat to native biodiversity in fresh waters. Alien freshwater molluscs may deplete the resources of native species and alter the physical structure of the habitat through their shell mass. These changes might have both positive and negative effects on native community members. We investigated the native macroinvertebrate community in relation to the densities of four alien mollusc species (Corbicula fluminea, Dreissena polymorpha, Potamopyrgus antipodarum and Lithoglyphus naticoides) in a sandy flat of Lake Neuchâtel, Switzerland. The habitat examined was dominated by these alien mollusc species. The abundance of the alien molluscs did not directly impact the native community assembly. However, C. fluminea and D. polymorpha influenced the composition and diversity of native macroinvertebrates by transforming the sandy substratum into a partly hard substratum habitat. Substantial differences in community composition between shallow (<3.5 m) and (≥5 m) deep sites were recorded. At shallow sites, the abundance of D. polymorpha was significantly reduced as a result of depth-selective feeding of ducks. A controlled shell decay study revealed that shells of alien molluscs (C. fluminea, D. polymorpha) persist for a longer period in the sediment than those of native molluscs. Consequently, shells of alien molluscs have a long-lasting impact by modifying the sandy habitat. This form of ecosystem engineering favours the occurrence of several native taxa, but is disadvantageous for other taxa with specific habitat requirements, and thus can be regarded as an indirect impact of competition.

Keywords: alien species - lake littoral - macroinvertebrates - Corbicula fluminea - Dreissena polymorpha - ecosystem engineer - SCUBA-diving

2012  Frequency of multiple paternity in the grass snake (Natrix natrix) — Meister B, Ursenbacher S & Baur B — Amphibia-Reptilia 33: 308–312   doi> 10.1163/156853812X634053 

Males can enhance their reproductive success through mating with multiple females. For females, however, one mating is usually sufficient to inseminate all of their ova. Females may benefit from multiple mating by producing genetically more diverse offspring, and by having the opportunity to choose sperm of the genetically most compatible male. We used five microsatellite loci to investigate the occurrence and frequency of multiple paternity in 11 clutches of the grass snake (Natrix natrix) in Switzerland. Using a very conservative estimate (program GERUD), two or more fathers were found in 27% of the clutches. However, based on the maximum likelihood estimate (program COLONY), multiple paternity occurred in 91% of the clutches with 2-5 contributing males per female. This is the first investigation demonstrating multiple paternity in a European natricine, with a frequency similar to those found in new world natricines.

Keywords: COLONY - GERUD - microsatellite DNA - Natricinae - paternity analysis

2012  Grass snake population differentiation over different geographic scales — Meister B, Ursenbacher S & Baur B — Herpetologica 68: 134–145   doi> 10.1655/HERPETOLOGICA-D-11-00036.1 

The loss and fragmentation of pristine habitat restrict specialized species to remnants of original habitat patches in a less suitable landscape. This may lead to a genetic differentiation of the subpopulations and to a decline in biodiversity. We used seven microsatellite markers to examine the genetic population structure of the grass snake, Natrix natrix (Linnaeus, 1758), sampled in remnants of pristine habitat in a former wetland in the Swiss lowlands and in a rural valley in the Alps. On a regional level, the population structures of N. natrix in these two areas were compared with that of grass snakes living in an intensively used agricultural area. The three study areas were 30–100 km apart, but were interconnected by the river Aare. At the local scale, no genetic differentiation was found in either of the N. natrix populations inhabiting the rural alpine valley or the intensively used agricultural area. However, two subpopulations in the former wetland area were genetically differentiated with a low but significant FST. This slight genetic differentiation can be explained by isolation by distance. At the regional scale, we found significant genetic differentiation between N. natrix populations inhabiting areas separated by 30–100 km. The genetic structure was highly related to isolation by distance with 85% of the among-populations genetic variance explained by the geographical distance between subpopulations. Euclidian distance explained genetic differentiation of grass snake populations better than the distance following watercourses. Our findings indicate regular gene flow between N. natrix subpopulations and show that this species also moves across intensively used terrestrial habitat. The genetic structure of grass snakes is mainly affected by geographic distance, while human activity and habitat alteration do not seem to reduce the snakes' movements. Our results suggest that conservation actions in human-altered landscapes should focus on the maintenance of a habitat mosaic with anuran breeding ponds and adequate oviposition sites.

Keywords: grass snake - isolation by distance - microsatellite DNA - Natrix natrix - population structure

2012  Garden waste deposits as a source for invasive plants in mixed-deciduous forests in Switzerland — Rusterholz H-P, Wirz D & Baur B — Applied Vegetation Science 15: 329–337   doi> 10.1111/j.1654-109X.2011.01175.x 

Question: Is illegal garden waste dumping in mixed deciduous forests a source for establishment of non-native plants in deciduous forests?
Location: Northwestern Switzerland.
Methods: We quantified the amount of illegally dumped garden waste at 20 sites over 1 yr and compared the soil conditions, species richness and abundance of plants in the ground vegetation at disposal sites with those at 20 control sites in urban deciduous forests.
Results: We found that illegal garden waste dumping frequently occurs in urban forests. At single sites, 0.1–12.5 m3 (mean: 2.6 m3) garden waste was dumped per month, resulting in a total annual amount of 2.2–35.8 m3 (mean: 17.8 m3) waste deposited. Thirty-seven of the 163 plant species recorded were not native to Switzerland. All 37 non-native species were recorded in waste disposal sites, but only three of them in control sites. Thus, garden waste dumping sites harboured a larger number of non-native species than control sites, but the two groups of sites did not differ in number of native species. The species composition also differed between disposal and control sites: larger proportions of species typical of disturbed habitats, more therophytes and species with autochorous seed dispersal were recorded in disposal sites than in control sites.
Conclusions: We provide evidence that numerous non-native horticultural plant species escape from dumping sites and colonize forests. There is an urgent need to increase awareness of garden owners concerning problems associated with illegal garden waste dumping.

2012  Population structure and genetic diversity of relict populations of Alyssum montanum on limestone cliffs in the Northern Swiss Jura mountains — Rusterholz H-P, Aydin D & Baur B — Alpine Botany 122: 109–117   doi> 10.1007/s00035-012-0105-0 

Exposed cliffs in the Northern Swiss Jura mountains harbour a highly diverse flora with numerous rare and relict plant species. The genetic structure of cliff populations is of particular interest because in a variety of plant species the populations are small, isolated and separated from their main distribution area in the Alps and the Mediterranean. We examined possible relationships between population size and size structure, sexual reproduction and genetic diversity of Alyssum montanum, a relict plant species occurring on limestone cliffs in the Northern Swiss Jura mountains. The population size of A. montanum ranged from 8 to 248 plant individuals on the 12 cliffs examined. Most populations contained a high proportion of small-sized (=young) plants indicating a successful establishment of seedlings. Fitness-related traits of A. montanum (percentage of reproductive individuals, number of fruits, fruit weight) varied widely between cliffs and were neither related to the size of the populations nor to the percentage of vegetation cover on the cliffs. RAPD-PCR analysis revealed that A. montanum populations exhibit a remarkably high genetic diversity. However, genetic diversity decreased with decreasing population size. Moreover, the positive relationship found between genetic variability and fitness-related traits indicates that population size is a key factor for the persistence of A. montanum on limestone cliffs.

Keywords: population size - RAPD-PCR - relict plant - sexual reproduction

2012  Response of plant and gastropod species to knotweed invasion — Stoll P, Gatzsch K, Rusterholz H-P & Baur B — Basic and Applied Ecology 13: 232–240   doi> 10.1016/j.baae.2012.03.004 

Invasive species of the knotweed complex (Fallopia sp.) have repeatedly been shown to decrease diversity of native local biota. While effects on plant species richness are well established, effects on invertebrate and in particular gastropod species richness are less well understood. We recorded cover of plant species and diversity and abundance of gastropodspecies in four plots (1 m × 1 m) with Fallopia japonica and compared these to paired control plots without F. japonica at 15 sites along the river Birs (Switzerland) in early summer (June) and autumn (September). Knotweed and control plots did not differ in site characteristics and soil parameters.
Average plant species richness in F. japonica plots was 50% lower compared to control plots. This reduction was significant for woody species as well as for herbaceous species. However, species richness of early flowering annuals did not differ significantly. Among the species most affected by knotweed were hop (Humulus lupulus) and European spindle tree (Euonymus europaeus) but also stand-forming species such as nettle (Urtica dioica) or ground elder (Aegopodium podagraria).
Average snail species richness was significantly reduced in F. japonica plots. The reduction was pronounced in large (≥5 mm shell size) and long-lived (>2 years) snail species but not in slugs or small and short-lived snails. For example, large snails such as the Roman snail (Helix pomatia, -85%) or the red-listed speciesBradybaena fruticum (-93%), showed reduced abundances in F. japonica compared to control plots. In contrast, the red-listed but small Vertigo pusilla (+92%) had higher abundances in F. japoinca plots. Principal component analyses revealed little overlap in plant communities or community composition of large snail species between F. japonica and control plots. Taken together, knotweedinvasion decreased the cover of most plantspecies and abundance of large and long-lived gastropods.

Keywords: biodiversity - exotic - Fallopia - invasive - Reynoutria - riparian habitat

2012  Vernetzte Oekoflächen fördern Heuschrecken — Duss M, Meichtry-Stier KS, Pasinelli G, Baur B & Birrer S — Agrarforschung Schweiz 3: 4–11

Keywords: ecological compensation area - habitat connectivity - grasshoppers - field cricket - large gold grasshopper

2012  Intensity of parasitic mite infection decreases with hibernation duration of the host snail — Häussler EM, Piza J, Schmera D & Baur B — Parasitology 139: 1038–1044   doi> 10.1017/S0031182012000327 

Temperature can be a limiting factor on parasite development. Riccardoella limacum, a haematophagous mite, lives in the mantle cavity of helicid land snails. The prevalence of infection by R. limacum in populations of the land snail Arianta arbustorum is highly variable (0-78%) in Switzerland. However, parasitic mites do not occur in host populations at altitudes of 1290 m or higher. It has been hypothesized that the host's hibernation period might be too long at high elevations for mites and their eggs to survive. To test this hypothesis, we experimentally infected snails and allowed them to hibernate at 4°C for periods of 4-7 months. Winter survival of host snails was negatively affected by R. limacum. The intensity of mite infection decreased with increasing hibernation duration. Another experiment with shorter recording intervals revealed that mites do not leave the host when it buries in the soil at the beginning of hibernation. The number of mites decreased after 24 days of hibernation, whereas the number of eggs attached to the lung tissue remained constant throughout hibernation. Thus, R. limacum survives the winter in the egg stage in the host. Low temperature at high altitudes may limit the occurrence of R. limacum.

2012  Does functional redundancy of communities provide insurance against human disturbances? An analysis using regional-scale stream invertebrate data — Schmera D, Baur B & Erős T — Hydrobiologia 693: 183–194   doi> 10.1007/s10750-012-1107-z 

Human-induced reductions in species richness might alter the quality of ecosystem services when the remaining species are not able to substitute the functions provided by extirpated species. We examined how human disturbances (nutrient enrichment, land use intensification, instream habitat degradation and the presence of alien species) influence the species richness of stream invertebrates. Stream invertebrates (425 native species) were collected by kick and sweep sampling technique at 274 stream sites covering the entire area of Hungary. We measured the species richness, functional richness (i.e. number of unique functional roles provided by community members) and functional redundancy (i.e. the functional insurance of the community) using information on the feeding habits of each species. To remove the effect of natural variability, we tested the effect of stressors on the residuals of models relating species richness, functional richness and functional redundancy with natural environmental gradients. Our results showed that species richness was negatively influenced by instream habitat degradation and nutrient enrichment. Independent of the way of quantifying functional richness and functional redundancy, we found that functional richness is more sensitive to human impact than functional redundancy of stream invertebrates. The finding that a reduction of species richness is associated with a loss of unique functional roles (functional richness) is important for conservation issues, because the number of unique functional roles is usually regarded as driver of ecosystem functioning.

2011  Effects of long-term trampling on the above-ground forest vegetation and soil seed bank at the base of limestone cliffs — Rusterholz H-P, Verhoustraeten C & Baur B — Environmental Management 48: 1024–1032   doi> 10.1007/s00267-011-9727-z 

Exposed limestone cliffs in central Europe harbor a highly divers flora with many rare and endangered species. During the past few decades, there has been increasing recreational use of these cliffs, which has caused local environmental disturbances. Successful restoration strategies hinge on identifying critical limitations. We examined the composition of aboveground forest vegetation and density and species composition of seeds in the soil seed bank at the base of four limestone cliffs in mixed deciduous forests that are intensively disturbed by human trampling and at four undisturbed cliffs in the Jura Mountains in northwestern Switzerland. We found that long-term human trampling reduced total aboveground vegetation cover at the base of cliffs and caused a significant shift in the plant-species composition. Compared with undisturbed cliffs, total seed density was lower in disturbed cliffs. Human trampling also altered the species composition of seeds in the soil seed bank. Seeds of unintentionally introduced, stress-tolerant, and ruderal species dominated the soil seed bank at the base of disturbed cliffs. Our findings indicate that a restoration of degraded cliff bases from the existing soil seed bank would result in a substantial change of the original unique plant composition. Active seed transfer, or seed flux from adjacent undisturbed forest areas, is essential for restoration success.

Keywords: deciduous forest - recreational disturbance - restoration - species composition - sport climbing

2011  Basel Zoo and its native biodiversity between the enclosures: a new strategy of cooperation with academic institutions — Baur B — International Zoo Yearbook 45: 48–54   doi> 10.1111/j.1748-1090.2010.00118.x 

In many zoos, the area separating the enclosures of zoo animals harbours highly diverse communities of freeliving animals and plants. These organisms have received little attention so far. Using an all-taxa-biodiversity inventory approach, a team of 46 zoologists and botanists carried out a 3 year study to assess the free-living organisms (plants, fungi, animals) occurring in the areas between the enclosures of zoo animals at Basel Zoo. A total of 3110 free-living species could be documented in this relatively small city zoo. However, not all taxonomical groups could be considered, mainly owing to the lack of experts. It was estimated that the actual richness of free-living species in Basel Zoo may exceed 5500. Thus, the number of free-living species is approximately eight to ten times higher than the 646 species of zoo animals maintained at Basel. The findings are important for preserving both the valuable remnants of natural and semi-natural habitats and threatened free living species at the Zoo. The project combines research and outreach, which can improve the understanding of native biodiversity while simultaneously raising the awareness of the threats to it. The success of sustainable garden management in protecting native biodiversity may motivate the public to aspire to their own 'wildlife friendly' gardening activities.

Keywords: all-taxa-biodiversity-inventory - botanists - conservation - ecosystems - habitat conservation - native species - volunteer - zoologists

2011  Snail herbivory decreases cyanobacterial abundance and lichen diversity along cracks of limestone pavements — Fröberg L, Stoll P, Baur A & Baur B — Ecosphere 2: art38   doi> 10.1890/ES10-00197.1 
Artikel als pdf Datei herunterladen

Herbivores are known to decrease plant species diversity in ecosystems with low productivity. Limestone pavements are low-productive habitats harboring specialized communities of cyanobacteria, and endo- and epilithic lichens exposed to extreme temperature and humidity fluctuations. Pavements of the Great Alvar (Öland, Sweden) are covered by free-living cyanobacteria giving the rock surface a dark color. Based on cyanobacterial abundance along the edges, two types of cracks intersecting the pavements have been described: Type one with abundant cyanobacteria and type two without cyanobacteria resulting in light-colored edges. Erosion and different lengths of inundation by melt water have been suggested to cause the conspicuous differences in community composition and hence color between cracks. We hypothesized that this pattern results from the grazing activity of the cyanobacteria- and lichen-feeding snail Chondrina clienta, which reduces cyanobacterial cover along light-colored cracks and facilitates endolithic lichens. Three dark and three light-colored cracks were investigated at each of three localities. Crack characteristics (i.e., aspect, width, depth and erosion) and snail density were assessed at the crack level. Cyanobacterial cover and lichen diversity were recorded in 1-cm sections, sampled every 5 cm along eight 160-cm-long transects per crack. Model selection was applied to estimate effects of snail density and distance from crack edges on cyanobacterial abundance and lichen diversity. Crack characteristics explained no differences in cyanobacterial cover or lichen diversity. However, cyanobacterial cover decreased towards the edges of cracks with high snail densities. A transplant experiment supported the correlational evidence. The abundant cyanobacterial cover on pieces of stone placed close to cracks with high snail densities was completely grazed within 19 months. By contrast, cyanobacteria recolonized initially completely grazed pieces of stone when fixed near cracks without snails. Abundance and diversity of endolithic lichens increased along cracks with high compared to low snail densities but decreased in epilithic lichens and lichens with cyanobacterial symbionts. However, the presence of the gastropod herbivore decreased overall lichen diversity. Comparing presence-absence matrices with null models revealed that species co-occurred less frequently than expected. Taken together, we provide evidence that herbivory indirectly released endolithic lichens from competition for light by reducing cyanobacterial cover.

Keywords: bioweathering - cyanobacteria - epilithic lichen - herbivory - spatial pattern

2011  Testing a typology system of running waters for conservation planning in Hungary — Schmera D & Baur B — Hydrobiologia 665: 183–194   doi> 10.1007/s10750-011-0621-8 

Landscape and site classifications are increasingly being used in conservation planning and biodiversity management. We examined the utility of a simple typology system for predicting the conservation value of running-water sites in Hungary using aquatic invertebrates. Aquatic invertebrates (444 species) were collected by kick and sweep sampling technique, in a few cases also with a net, at 317 running-water sites covering the entire area of Hungary. On the basis of three criteria (naturalness, altitude and size of catchment area) we obtained a typology scheme distinguishing five running-water types: artificial lowland stream, natural highland river, natural highland stream, natural lowland river and natural lowland stream. We expressed the conservation value of each site using the numbers of native species, unique native species, red-list species, protected species and alien species. Furthermore, the conservation value of each river type was expressed by a measure of beta diversity. Our results show that any interpretation of the effect of a single criterion might be misleading. Consequently, the use of the whole typology system is recommended. The study revealed that all stream types are valuable to a certain extent because they maintain distinct biological communities. We found that the conservation value of artificial watercourses is comparable to that of natural running-water sites. We identified that natural lowland rivers and artificial lowland streams are the ones mostly exposed to species invasions. These findings are essential in maintaining and protecting conservation values of any freshwater ecosystem, and may contribute to management decisions on running waters in Hungary.

Keywords: alien species - aquatic invertebrates - artificial habitat - biodiversity assessment - conservation value - running waters - typology

2011  Partial precopulatory isolation between two geographically distant populations of the land snail Arianta arbustorum (L.) — Kupfernagel S & Baur B — Journal of Molluscan Studies 77: 87–94   doi> 10.1093/mollus/eyq041 

Different mechanisms of reproductive isolation were examined in the simultaneously hermaphroditic land snail Arianta arbustorum. Snails from two geographically isolated populations in the Swiss Alps were allowed to copulate with both a homotypic (individual from the same population) and a heterotypic (individual from the other population) partner (in half of the pairs in reversed order). Control snails mated twice with a homotypic partner. In the first mating, successful copulations occurred in a lower frequency in heterotypic pairs (55.6%) than in homotypic pairs (82.9%). Heterotypic pairs that eventually copulated showed more breaks during courtship than homotypic pairs. However, neither the number of eggs produced nor their hatching success was influenced by the type of mating partner. In the second mating, the sequence of different partners had an effect on the proportion of successful copulations in snails from one geographical population. Snails that copulated first with a homotypic partner remated more frequently with a homotypic partner than snails that copulated first with a heterotypic partner. Paternity analyses of progeny of snails that mated twice indicate no influence of the origin of the mating partner. The proportion of hatchlings sired by the second mate (P2) averaged 0.39, indicating a slight first-mate advantage. However, highly skewed paternity patterns were found in the progeny of 44.4% of the double-mated snails. Genetic analyses also revealed a low frequency of self-fertilization (3.7%). These findings indicate the presence of partial precopulatory isolation between two distant snail populations, although reproductive compatibility is still maintained.

2011  Survival of the invasive clam Corbicula fluminea (Müller) in response to winter water temperature — Müller O & Baur B — Malacologia 53: 367–371

Water temperature plays a crucial role in determining the distribution of aquatic organisms because most are ectothermic. The further spread of the invasive Asian clam Corbicula fluminea, a species causing enormous damage to water intake pipes and electric power plant cooling systems, has been assumed to be limited due to intolerance of very cold water, with a lower lethal temperature of about 2 degrees C. In recent years, however, C. fluminea invaded most of the major rivers in Europe, including sections where the water temperature falls below 2 degrees C for short periods during winter. Here we quantify the cold tolerance of C. fluminea in a controlled laboratory experiment. We show that C. fluminea has a greater cold tolerance than previously assumed. In water of 0 degrees C, clam survival decreased from 100% to 17.5% with increasing exposure from 4 to 9 weeks. Considering actual water temperatures of rivers during winter and ongoing stream warming, we conclude that this invasive clam will establish in a wider range of waterbodies in Europe than previously predicted.

Keywords: species distribution - cold tolerance - species survival - ectothermic - winter water temperature

2011  Citizen science reveals unexpected continental-scale evolutionary change in a model organism — Silvertown J, Cook L, Cameron R, Dodd M, McConway K, Worthington J, Skelton P, Anton C, Bossdorf O, Baur B, Schilthuizen M, Fontaine B, Sattmann H, Bertorelle G, Correia M, Oliveira C, Pokryszko B, Ozgo M, Stalazas A, Gill E, Rammul U, Solymos P, Feher Z & Juan X — PLoS ONE 6: e18927   doi> 10.1371/journal.pone.0018927 

Organisms provide some of the most sensitive indicators of climate change and evolutionary responses are becoming apparent in species with short generation times. Large datasets on genetic polymorphism that can provide an historical benchmark against which to test for recent evolutionary responses are very rare, but an exception is found in the brown-lipped banded snail (Cepaea nemoralis). This species is sensitive to its thermal environment and exhibits several polymorphisms of shell colour and banding pattern affecting shell albedo in the majority of populations within its native range in Europe. We tested for evolutionary changes in shell albedo that might have been driven by the warming of the climate in Europe over the last half century by compiling an historical dataset for 6,515 native populations of C. nemoralis and comparing this with new data on nearly 3,000 populations. The new data were sampled mainly in 2009 through the Evolution MegaLab, a citizen science project that engaged thousands of volunteers in 15 countries throughout Europe in the biggest such exercise ever undertaken. A known geographic cline in the frequency of the colour phenotype with the highest albedo (yellow) was shown to have persisted and a difference in colour frequency between woodland and more open habitats was confirmed, but there was no general increase in the frequency of yellow shells. This may have been because snails adapted to a warming climate through behavioural thermoregulation. By contrast, we detected an unexpected decrease in the frequency of Unbanded shells and an increase in the Mid-banded morph. Neither of these evolutionary changes appears to be a direct response to climate change, indicating that the influence of other selective agents, possibly related to changing predation pressure and habitat change with effects on micro-climate.

2011  Genetic differences between the two remaining wild populations of the endangered Indian rhinoceros (Rhinoceros unicornis) — Zschokke S, Armbruster GFJ, Ursenbacher S & Baur B — Biological Conservation 144: 2702–2709   doi> 10.1016/j.biocon.2011.07.031 

The management of rare and endangered species in the wild and in captivity requires an understanding of the characterization of the genetic units within each species and their relationships to each other. The Indian rhinoceros (Rhinoceros unicornis) is an endangered species with a current population size of c. 2800 individuals. We analyzed 26 individuals of known origin kept in captivity and 21 wild ranging individuals of the two remnant large wild populations in Assam (India) and Nepal employing mitochondrial and microsatellite markers to determine whether the two geographically isolated populations show distinct patterns of genetic diversity, and whether the genetic diversity of the populations is influenced by past demographic bottlenecks. We identified 10 different mitochondrial D-loop haplotypes, of which 4 were specific to the Assam population (10 sequences examined) and 6 specific to the Nepal population (19 sequences). Similarly, the microsatellite analysis demonstrated a strong genetic differentiation between the Assam and Nepal populations and allowed to assign each individual to its origin with high confidence. Furthermore, our analyses revealed the occurrence of a bottleneck in the Assam population long before the reported bottleneck in 1908, and it revealed that the Nepal population is a recent (probably post-glacial) colonization. In summary, the extent of genetic divergence between the two remnant R. unicornis populations suggests separate conservation programs (even for captive individuals) as long as the persistence of the entire species is not severely threatened. The microsatellite markers can also be used to determine the origin of confiscated material such as horns.

Keywords: bottleneck - microsatellite markers - mitochondrial D-loop - population genetics - population management

Microsatellite genotypes of the analysed individuals

2011  Determinants of female and male reproductive success in a simultaneous hermaphrodite land snail — Minoretti N, Schmera D, Kupfernagel S, Zschokke S, Armbruster GFJ, Beese K, Baur A & Baur B — Animal Behaviour 82: 707–715   doi> 10.1016/j.anbehav.2011.06.026 

Classical sexual selection theory assumes that the reproductive success of females is limited by the resources available for egg production, while the reproductive success of males is determined by the number of mates (Bateman's principle). It has been suggested that the optimal mating rates should also diverge between gender functions within individuals of simultaneous hermaphrodites. We assessed determinants of mating success and female and male reproductive success in individuals of the simultaneous hermaphrodite land snail Arianta arbustorum. We videorecorded the behaviour of individually tagged snails kept in groups of six animals over one reproductive period (58 days) and assigned the genotyped hatchlings to the female and male function of individual parents. We found considerable interindividual variation in the activity of snails, which is a combined measure of time spent crawling, feeding and digging. The snails mated between zero and three times. Mating success, which is equal to the female and male function in simultaneous hermaphrodites with reciprocal copulation, was mainly determined by the activity of an individual. We found that female reproductive success (number of hatchlings emerging from the eggs laid by the focal snail) was positively correlated with male reproductive success (number of hatchlings sired by the focal snail) and that both were determined by the individual's activity. Furthermore, both female and male reproductive success of an individual were influenced positively by the snail's degree of genetic heterozygosity and negatively by shell size. Our results challenge the trade-off assumption of sex allocation theory in simultaneous hermaphrodites.

Keywords: Arianta arbustorum - gastropod - mating success - multiple mating - paternity - reproductive success - sex allocation - simultaneous hermaphrodite

2011  Biodiversität in der Schweiz: Wandel, Zustand, Handlungsbedarf — Baur B, Duelli P, di Giulio M, Gonseth Y, Klaus G, Lachat T, Lambelet C, Nentwig W, Pauli D, Pearson S, Peter A, Scheidegger C, Vittoz P, Walter T & Wiedmer E — Forum Biodiversität Schweiz, Akademien der Wissenschaften, Bern, 27 Seiten
Artikel als pdf Datei herunterladen

Drei Jahre lang haben 82 Wissenschaftlerinnen und Wissenschaftler, Fachexpertinnen und Fachexperten Daten zum Wandel der Biodiversität in der Schweiz seit 1900 zusammengetragen und analysiert. Die Ergebnisse der Studie wurden im Internationalen Jahr der Biodiversität 2010 als Buch veröffentlicht. Die vorliegende Broschüre fasst die wichtigsten Resultate und Kernbotschaften zusammen.

2011  Sperm utilization in subadult and adult simultaneous hermaphrodite snails mating in the wild — Kupfernagel S & Baur B — Canadian Journal of Zoology 89: 1041–1049   doi> 10.1139/Z11-080 

In species with multiple mating and long-term sperm storage, males are expected to show a preference for mating with virgin and young females to reduce the risk of sperm competition. In various simultaneous hermaphrodite land snail species, sperm production precedes egg production by 2-4 weeks, resulting in a short period of protandric hermaphroditism before shell growth is completed. In a natural population, we collected copulating pairs of the simultaneous hermaphrodite land snail Arianta arbustorum (L., 1758) consisting either of two adults, of two subadults, or of one adult and one subadult snail, and determined the paternity of their hatchlings that emerged from subsequently deposited eggs. Adult snails used sperm received from subadult mating partners for egg fertilization in the same frequency as sperm from adults, indicating that subadult and adult snails do not differ in male function. Furthermore, an unfinished shell is not a reliable indicator for virginity, because 35% of the subadult individuals had already sperm stored from previous mating(s). Compared with adults, young individuals exhibited a lower risk of sperm competition, indicated by a higher last mate sperm precedence. However, subadult snails produced fewer eggs than adult snails, counteracting the evolutionary advantage of preferring a young partner with low sperm competition risk.

2010  High population differentiation in the rock-dwelling land snail (Trochulus caelatus) endemic to the Swiss Jura mountains — Ursenbacher S, Alvarez C, Armbruster GFJ & Baur B — Conservation Genetics 11: 1265–1271   doi> 10.1007/s10592-009-9956-3 

Understanding patterns of genetic structure is fundamental for developing successful management programmes for isolated populations of threatened species. Trochulus caelatus is a small terrestrial snail endemic to calcareous rock cliffs in the Northwestern Swiss Jura Mountains. Eight microsatellite loci were used to assess the effect of habitat isolation on genetic population structure and gene flow among nine populations occurring on distinct cliffs. We found a high genetic differentiation among populations (mean F ST = 0.254) indicating that the populations are strongly isolated. Both allelic richness and effective population size were positively correlated with the size of the cliffs. Our findings support the hypothesis that T. caelatus survived on ice-free cliffs during the Pleistocene glacier advancements from the Alps. Due to the establishment of beech and pine forest under recent, temperate climate conditions, dispersal between cliffs is no longer possible for rock-dwelling snails such as T. caelatus. Our results provide basic data for developing a conservation action plan for this endangered gastropod species

Keywords: Helicoidea - Land snails - microsatellites - population genetic structure Trochulus caelatus

2010  Variation in multiple paternity and sperm utilization patterns in natural populations of a simultaneous hermaphrodite land snail — Kupfernagel S, Rusterholz H-P & Baur B — Biological Journal of the Linnean Society 99: 350–361   doi> 10.1111/j.1095-8312.2009.01361.x 

Mating frequency has important implications for patterns of sexual selection and sexual conflict, and hence for issues such as the maintenance of genetic diversity and speciation. We assessed the level of multiple paternity and sperm utilization patterns in four natural populations of the simultaneous hermaphrodite land snail Arianta arbustorum using four polymorphic microsatellite loci. A total of 1088 offspring from 26 wild-caught snails were genotyped to determine the number of fathers siring each brood and paternity skew in succeeding clutches. Multiple paternity was detected in the offspring of all 26 mother snails examined with the contribution of two to six fathers. The four populations examined differed in the level of multiple paternity. Snails in the population with the highest density of adults showed the highest level of multiple paternity, whereas snails in the population with the lowest density exhibited the lowest value of multiple paternity. Highly skewed paternity patterns were found in the progeny of 15 (57.7%) of the 26 mother snails. The number and identity of fathers siring the offspring of single mothers also varied among successive clutches. Furthermore, genetic analyses indicate a low level of self-fertilization in one of the four populations.

Keywords: Arianta arbustorum - Gastropoda - mating frequency - paternity analysis - population density - self-fertilization

2010  Delayed response in a plant-pollinator system to experimental grassland fragmentation — Rusterholz H-P & Baur B — Oecologia 163: 141–152   doi> 10.1007/s00442-010-1567-7 

The fragmentation of natural habitat is considered to be a major threat to biodiversity. Decreasing habitat quality and quantity caused by fragmentation may lead to a disruption of plant-pollinator interactions and to a reduction in sexual reproduction in plant species. We conducted a 6-year field experiment to investigate the effects of small-scale fragmentation on plant-pollinator interactions and genetic diversity in the self-compatible Betonica officinalis. We examined the abundance and composition of pollinators, the foraging behaviour of bumblebees and the performance, outcrossing rate and genetic diversity of B. officinalis after 2 and 6 years in experimentally fragmented nutrient-poor, calcareous grassland in the northern Swiss Jura mountains. Fragments of different size (2.25 and 20.25 m²) were isolated by a 5-m-wide strip of frequently mown vegetation. Control plots of corresponding size were situated in adjacent undisturbed grassland. Experimental grassland fragmentation altered the composition of B. officinalis pollinators and reduced their flower visitation rate. Furthermore, the foraging behaviour of bumblebees was changed in the fragments. After 6 years of fragmentation seed weight was higher in fragments than in control plots. However, the densities of B. officinalis rosettes and inflorescences, plant height and inflorescence length were not affected by fragmentation. The outcrossing frequency of B. officinalis growing in fragments was reduced by 15% after 2 years and by 33% after 6 years of experimental fragmentation. This resulted in a significant reduction of the genetic diversity in seedlings emerging in fragments after 6 years. Our study shows that small-scale habitat fragmentation can disturb the interaction between B. officinalis and pollinators resulting in a reduced outcrossing frequency and genetic diversity in plants growing in fragments. However, the response to fragmentation was considerably delayed. This finding strengthens the claim for long-term field experiments with proper replications and controls to assess delayed effects of habitat fragmentation.

Keywords: Betonica officinalis - genetic diversity - pollinator foraging behaviour - outcrossing frequency - self-compatibility

2010  Contact-based transmission models in terrestrial gastropod populations infected with parasitic mites — Schüpbach HU & Baur B — International Journal for Parasitology 40: 1045–1050   doi> 10.1016/j.ijpara.2010.02.012 

Parasite transmission fundamentally affects the epidemiology of host–parasite systems, and is considered to be a key element in the epidemiological modelling of infectious diseases. Recent research has stressed the importance of detailed disease-specific variables involved in the transmission process. Riccardoella limacum is a hematophagous mite living in the mantle cavity of terrestrial gastropods. In this study, we experimentally examined whether the transmission success of R. limacum is affected by the contact frequency, parasite load and/or behaviour of the land snail Arianta arbustorum, a common host of R. limacum. In the experiment the transmission success was mainly affected by physical contacts among snails and slightly influenced by parasite intensity of the infected snail. Using these results we developed two different transmission models based on contact frequencies and transmission probability among host snails. As parameters for the models we used life-history data from three natural A. arbustorum populations with different population densities. Data on contact frequencies of video-recorded snail groups were used to fit the density response of the contact function, assuming either a linear relationship (model 1) or a second-degree polynomial relationship based on the ideal gas model of animal encounter (model 2). We calculated transmission coefficients (β), basic reproductive ratios (R0) and host threshold population densities for parasite persistence in the three A. arbustorum populations. We found higher transmission coefficients (β) and larger R0-values in model 1 than in model 2. Furthermore, the host population with the highest density showed larger R0-values (16.47–22.59) compared to populations with intermediate (2.71–7.45) or low population density (0.75–4.10). Host threshold population density for parasite persistence ranged from 0.35 to 2.72 snails per m2. Our results show that the integration of the disease-relevant biology of the organisms concerned may improve models of host–parasite dynamics.

Keywords: parasite transmission - epidemiology - basic reproductive ratio -transmission model - Riccardoella limacum - Arianta arbustorum

2010  Spatial genetic analysis of the grass snake, Natrix natrix (Squamata: Colubridae), in an intensively used agricultural landscape — Meister B, Hofer U, Ursenbacher S & Baur B — Biological Journal of the Linnean Society 101: 51–58   doi> 10.1111/j.1095-8312.2010.01474.x 

Both the conversion of natural habitats to farmland and efforts at increasing the yield of existing crops contribute to a decline in biodiversity. As a consequence of land conversion, specialised species are restricted to remnants of original habitat patches, which are frequently isolated. This may lead to a genetic differentiation of the subpopulations. We used seven microsatellite markers to examine the genetic population structure of the grass snake, Natrix natrix (Linnaeus, 1758), sampled in remnants of pristine habitat embedded in an intensively used agricultural landscape in north-western Switzerland. The study area, a former wetland, has been drained and gradually converted into an agricultural plain in the last century, reducing the pristine habitat to approximately 1% of the entire area. The grass snake feeds almost entirely on amphibians, and is therefore associated with wetlands. In Central Europe, the species shows severe decline, most probably as a result of wetland drainage and decrease of amphibian populations. We found no genetically distinct grass snake populations in the study area covering 90 km². This implies that there is an exchange of individuals between small remnants of original habitat. Thus, gene flow may prevent any genetic differentiation of subpopulations distributed over a relatively large area. Our results show that a specialized snake species can persist in an intensively used agricultural landscape, provided that suitable habitat patches are interconnected.

Keywords: fragmentation - intensive agriculture - Natrix natrix - population genetic structure

2010  Biodiversität — Baur B — UTB Profile. Haupt Verlag, Bern, 127 Seiten

Was bedeutet Biodiversität und warum ist sie wichtig für die Menschen? Bruno Baur erklärt grundlegende Aspekte der Biodiversität und erläutert Prozesse, die zu Veränderungen in der Vielfalt des Lebens auf unserem Planeten führen. Ein verständlicher Einstieg für Studierende der Biologie, Ökologie, Geografie, Raumplanung, Umwelt-, Agrar- und Forstwissenschaften, Ressourcenmanagement, Ökonomie, Politologie und Ethik.

ISBN 978-3-8252-3325-9

2010  Within- and among-family variation in parasite load and parasite-induced mortality in the land snail Arianta arbustorum, a host of parasitic mites — Schüpbach HU & Baur B — Journal of Parasitology 96: 830–832   doi> 10.1645/GE-2315.1 

Variation in host susceptibility and parasite-induced mortality are preconditions for parasite-related selection on host populations. In terrestrial gastropods, variation in resistance against ectoparasite infection is poorly understood. We examined the within- and among-family variation in parasite load in full-siblings of the land snail Arianta arbustorum experimentally infected with Riccardoella limacum, a mite living in the mantle cavity of helicid land snails. We also quantified the influence of family origin and host size on parasite load and calculated its heritability (h2). Furthermore, we examined the influence of parasite load, snail size and family origin on host winter mortality, an important life-history trait of A. arbustorum. Parasite load was heritable (h2 = 0.63). In infected snails, parasite load was affected by family origin and increased with increasing shell size. Host mortality during hibernation increased with increasing parasite load and differed among families, but was not affected by snail size. Our results show high among-family variation both in resistance against ectoparasite infection and in host winter mortality. Furthermore, we show that parasite load is linked to snail size, which suggests that the proliferation of R. limacum is limited by resources provided by A. arbustorum

2010  Native and alien macroinvertebrate richness in a remnant of the former river Rhine: a source for recolonisation of restored habitats? — Wirth A, Schmera D & Baur B — Hydrobiologia 652: 89–100   doi> 10.1007/s10750-010-0321-9 

Rivers are among the most endangered ecosystems of the world with dramatically decreasing biodiversity. Rehabilitation programmes aiming at restoration of riverine ecosystems rely on the recolonisation of native macroinvertebrates from refuges. We examined whether a relatively natural remnant of the former river Rhine (Altrhein) harbours a higher richness of benthic macroinvertebrates than two sites of the modified Rhine with artificial and semi-natural embankments near Basel. All three sites were bimonthly sampled between May 2007 and May 2008 using three techniques: Kick and Sweep, drifting animals collected from pieces of stone turned by hand, and animals collected from stone surfaces. Taxa richness was higher in the Altrhein than in the two sampling sites in the river Rhine, but it was mainly a result of the large number of individuals sampled at this site. Despite 17% of taxa recorded were alien, the three sampling sites differed neither in the number of alien taxa nor in their abundances. However, lower percentages of both alien taxa and individuals were recorded in the Altrhein than at the other two sites in the Rhine. Indicator value analysis showed that the macroinvertebrate community of the Altrhein maintains several native and specific taxa. Multivariate analyses supported the separation of the communities collected at different sampling sites and also the uniqueness of the community in the Altrhein. The observed patterns, however, strongly depended on the sampling method applied, thereby calling the attention to the application of standard sampling methods and also to the restriction of result comparisons on projects using identical sampling methodology. Our study shows that the remnant of the former river Rhine serves as a refuge for macroinvertebrates which may facilitate future restoration of the river embankment.

Keywords: alien taxa - richness - conservation value - macroinvertebrates - river Rhine

2010  Ausbreitung des Buchsbaumzünslers Diaphania perspectalis (Lepidoptera, Pyralidae) in der Region Basel - eine für die Schweiz neue Schädlingsart — Leuthardt FLG, Billen W & Baur B — Entomo Helvetica 3: 51–57
Artikel als pdf Datei herunterladen

The spread of D. perspectalis has been examined in the region of Basel over a period of six months. First results suggest the occurrence of three generations per year. Due to its rapid spread, D. perspectalis might colonize all suitable habitats in Switzerland within a few years.

Keywords: Diaphania perspectalis - Pyralidae - Buxus - Basel

2009  Effects of soil type and adult size on mating propensity and reproductive output in two populations of the land snail Arianta arbustorum (Linnaeus) — Baur A, Minoretti N & Baur B — Malacologia 51: 1–11

Life-history traits in terrestrial gastropods may be influenced by both abiotic and biotic factors. This study examines the effects of soil type and adult size (shell volume) on mating propensity and female and male reproductive output (number and mass of eggs, number of sperm delivered and spermatophore mass) in individuals of the simultaneous hermaphrodite land snail Arianta arbustorum from two populations kept both on calcium-(Ca-)rich and Ca-poor soil. Snails from the two populations differed in adult size, relative shell growth, mating propensity and egg size. Furthermore, in both populations the number of egg batches deposited, egg size and spermatophore size scaled allometrically with shell volume, but not the total number of eggs produced and number of sperm delivered. Independent of population and shell size, the type of soil on which the snails were maintained influenced mating propensity, the total number of eggs produced and the mass of the albumen gland (another measure of female reproductive output). The mating propensity was higher and the total number of eggs produced was larger in snails kept on Ca-poor soil than in individuals reared on Ca-rich soil. This surprising finding could be explained by the fact that the Ca-poor soil used in the experiment still contained enough Ca to allow reproduction, and that the snails ingested Ca through the food consumed (lettuce grown on Ca-rich soil was available ad libitum). Moreover, the Ca-rich soil could contain minerals or (unknown) substances which discourage reproduction in A. arbustorum. Our study highlights the complexities faced when interpreting differences in the life history of gastropods. Explaining interpopulational differences in life-history patterns requires not only the understanding of the influence of snail origin, but also an understanding of the effects of shell size, substratum type (soil type), food and local climate.

Keywords: Arianta arbustorum - calcium availability - egg size - reproductive allocation - simultaneous hermaphrodite - sperm number

2009  Evolution of female sperm storage organs in the carrefour of sylommatophoran gastropods — Beese K, Armbruster GFJ, Beier K & Baur B — Journal of Zoological Systematics and Evolutionary Research 47: 49–60   doi> 10.1111/j.1439-0469.2008.00491.x 

The presence of specialized female sperm-storage organs has been recognized as an important factor influencing postcopulatory sexual selection via sperm competition and cryptic female choice in internally fertilizing species. We morphologically examined the complexity of sperm-storage organs in the carrefour (spermatheca and fertilization pouch) in 47 species of stylommatophoran gastropods. We used partial 28S rDNA sequences to construct a molecular phylogeny, and applied maximum likelihood (ML) and Bayesian methods to investigate the history of spermatheca diversification and to test different hypotheses of sperm-storage organ evolution. The phylogenetic reconstruction supported several gains and losses of spermathecae. Moreover, a complex spermatheca was associated with the occurrence of love darts or other kinds of auxiliary copulatory organs, the presence of a long penial flagellum, and cross-fertilization as the predominant mating system. However, our results also suggest associations of carrefour complexity with body size, reproductive strategy (semelparity versus iteroparity), reproductive mode (oviparity versus ovoviviparity), and habitat type. Carrefour length in 17 snail species possessing a spermatheca was positively correlated with sperm length. Our results indicate that postcopulatory sexual selection as well as life history and habitat specificity may have influenced the evolution of female sperm-storage organs in hermaphroditic gastropods.

Keywords: comparative phylogenetic analysis - dart shooting - habitat - hermaphrodite - life history - mating system - postcopulatory sexual selection

2009  Effects of fire place use on forest vegetation and amount of woody debris in suburban forests in northwestern Switzerland — Hegetschweiler KT, van Loon N, Ryser A, Rusterholz H-P & Baur B — Environmental Management 43: 299–310   doi> 10.1007/s00267-008-9194-3 

Urban forests are popular recreation areas in Europe. Several of these temperate broad-leaved forests also have a high conservation value due to sustainable management over many centuries. Recreational activities, particularly the use of fireplaces, can cause extensive damage to soil, ground vegetation, shrubs, and trees. Firewood collection depletes woody debris, leading to a loss of habitat for specialized organisms. We examined the effects of fireplace use on forest vegetation and the amount of woody debris by comparing disturbed and control plots in suburban forests in northwestern Switzerland. At frequently used fireplaces, we found reduced species densities in the ground vegetation and shrub layer and changes in plant species composition due to human trampling within an area of 150–200 m². Picnicking and grilling also reduced the height and changed the age structure of shrubs and young trees. The amount of woody debris was lower in disturbed plots than in control plots. Pieces of wood with a diameter of 0.6–7.6 cm were preferentially collected by fireplace users. The reduction in woody debris volume extended up to a distance of 16 m from the fire ring, covering an area of 800 m² at each picnic site. In order to preserve the ecological integrity of urban forests and to maintain their attractiveness as important recreation areas, we suggest depositing logging residues to be used as firewood and to restrict visitor movements near picnic sites.

Keywords: picnicking - grilling - outdoor recreation - firewood collection - human trampling - nature conservation - sustainable forest management

2009  Disturbances by human trampling alter the performance, sexual reproduction and genetic diversity in a clonal woodland herb — Rusterholz H-P, Kissling M & Baur B — Perspectives in Plant Ecology Evolution and Systematics 11: 17–29   doi> 10.1016/j.ppees.2008.09.002 

Disturbances play a major role in structuring the community composition in a variety of ecosystems. The potential impact of disturbances on sexual reproduction and genetic diversity of plants has so far received little attention. We examined the effects of disturbance by human trampling on the performance, sexual reproduction and clonal diversity in the woodland herb Anemone nemorosa in six sites disturbed by intensive recreational activities and in six undisturbed sites in suburban forests in Switzerland. Disturbance by human trampling decreased shoot height of A. nemorosa and altered the size-dependent flowering probability function. Furthermore, in disturbed sites an increased percentage of aborted seeds was found, resulting in a reduced sexual reproductive potential of A. nemorosa populations. Both clonal and genetic diversity of A. nemorosa were reduced in disturbed sites. Our study shows for the first time that disturbance by human trampling can decrease the genetic diversity in a clonal woodland plant. This suggests that genetic aspects of woodland plants should be considered in restoring degenerated forest sites.

Keywords: Anemone nemorosa - clonal diversity - deciduous forests - disturbance - RAPD-PCR - recreation

2009  Novel microsatellite loci in the grass snake (Natrix natrix) and cross-amplification in the dice snake (Natrix tessellata) — Meister B, Armbruster GFJ, Frauenfelder N & Baur B — Molecular Ecology Resources 9: 604–606   doi> 10.1111/j.1755-0998.2008.02460.x 

Six novel polymorphic microsatellite loci are presented for the grass snake (Natrix natrix), a species with declining populations in many regions. The number of alleles per locus ranged from two to seven. Four dice snake (Natrix tessellata) microsatellites were polymorphic in the grass snake with three to four alleles. At two loci, the expected heterozygosity differed significantly from observed heterozygosity. Cross-amplification of the grass snake markers in the dice snake showed two polymorphic microsatellites with two and four alleles.

Keywords: conservation - dice snake - grass snake - microsatellites - Natrix natrix - Natrix tessellata

2009  Population dynamics of six land snail species in experimentally fragmented grassland — Stoll P, Oggier P & Baur B — Journal of Animal Ecology 78: 236–246   doi> 10.1111/j.1365-2656.2008.01478.x 

1. The fragmentation of natural habitats is generally considered to be a major threat to biodiversity. Different species may respond differently to habitat fragmentation, depending on species-specific traits such as body size, dispersal ability, mating system, and habitat requirement. 2. The population sizes and extinction and re-colonization frequencies of six naturally occurring land snail species (Cochlicopa lubrica, Vertigo pygmaea, Pupilla muscorum, Punctum pygmaeum, Helicella itala, and Trichia plebeia) were examined over 3 years in an experimentally fragmented nutrient-poor, calcareous grassland in the northern Swiss Jura mountains using a mark-recapture technique. Fragments of different size (0.25 m², 2.25 m², and 20.25 m²) were isolated by a 5-m wide strip of frequently mown vegetation. Control plots of corresponding size were situated in adjacent undisturbed grassland. 3. Experimental grassland fragmentation influenced the population size in all snail species except H. itala, which is the species with the biggest shell and it is also active under mild conditions in winter. However, fragmentation affected different species to a different extent. 4. Extinction (= disappearance from a plot) frequency increased with time, decreasing population size and decreasing plot size in all species. Large populations had a lower extinction probability than small populations. Fragmentation increased the probability of extinction, which also differed among snail species. The effect of plot size on extinction probability was still significant even after the effect of population size had been taken into account. 5. Fragments and control plots did not differ in re-colonization frequencies when all six species were considered. However, fragmentation influenced re-colonization frequency when the two species with large shells (H. itala and T. plebeia) were excluded from the analysis. 6. Our study shows that small-scale grassland fragmentation affects different land snail species to a different extent. This finding strengthens the claim for multi-species approaches to obtain general predictions of fragmentation impact.

Keywords: extinction - Gastropoda - multi-species approach - mark-recapture - re-colonization

2009  Intensive recreational activities in suburban forests: A method to quantify the reduction in timber value — Rusterholz H-P, Bilecen E, Kleiber O, Hegetschweiler KT & Baur B — Urban Forestry and Urban Greening 8: 109–116   doi> 10.1016/j.ufug.2009.02.002 

Central European forests are generally multifunctional; the same forest areas are used for timber production and recreation. In frequently visited areas damage to trees can be observed. We developed a method to estimate the actual reduction in timber value due to recreation-induced damage. The method was tested in two suburban (oak-hornbeam and beech) forests sustainably maintained by a selective management system and with free access in northwestern Switzerland. Considering the total forest areas, 9.4% of oak trees and 23.0% of beech trees were damaged by recreational activities. The resulting reduction in timber value averaged 19 and 53 (sic) ha(-1) a(-1) in the two forests. The annual reduction in timber value due to recreation-induced damage can account for up to 16% of the total proceeds. The monetary benefits of forest recreation in these areas, however, by far exceed the damage to trees.

Keywords: forest recreation - multifunctionality - tree damage - spatial distribution of damage

2009  Effects of small-scale grassland fragmentation and frequent mowing on population density and species diversity of orthopterans: a long-term study — Braschler B, Marini L, Thommen GH & Baur B — Ecological Entomology 34: 321–329   doi> 10.1111/j.1365-2311.2008.01080.x 

1. Habitat fragmentation is considered one of the major threats to invertebrate diversity in semi-natural grassland. However, the effects of habitat fragmentation through mowing on the rich insect fauna of these grasslands have not been sufficiently investigated and experiments are especially rare. 2. We studied the impact of small-scale grassland fragmentation on orthopterans over 7 years in an experiment which allowed us to additionally investigate the effect of frequent mowing on Orthoptera communities. 3. Overall, Orthoptera density and species richness increased over time. This was likely a result of increased small-scale habitat heterogeneity and the provision of a short-turf habitat suitable for xerophilous species. The fragmentation affected orthopteran density and species composition but not species richness whose response lagged behind the changes in abundance. 4. Responses differed between suborders. Ensifera density was higher in fragment than in control plots. Caelifera density did not differ between fragment and control plots. The mown matrix was an unsuitable habitat for most of the species, particularly within the Ensifera. 5. Our experiment shows that even small-scale fragmentation can affect Orthopteran communities and that the effects became more pronounced over time. As the mown matrix was unsuitable for many Ensifera species, they may go locally extinct when large areas are mown simultaneously.

Keywords: bush crickets - calcareous grasslands - crickets - disturbance - grasshoppers - habitat fragmentation - isolation - Jura mountains

2009  Short-term and long-term effects of human trampling on above-ground vegetation, soil density, soil organic matter and soil microbial processes in suburban beech forests — Kissling M, Hegetschweiler KT, Rusterholz H-P & Baur B — Applied Soil Ecology 42: 303–314   doi> 10.1016/j.apsoil.2009.05.008 

Understanding the effects of disturbance by human trampling on ecosystem processes is essential for themanagement of recreational areas. Discussions on recreational impacts are based either on data from trampling experiments or on field survey data from sites subjected to long-term recreational use, but rarely on a combination of both. We examined whether results from a short-term trampling experiment reflect the impact of long-term trampling around frequently used fire places. We compared short- and long-term effects of human trampling on above-ground forest vegetation and soil physical, chemical and microbial characteristics.We found both similarities and differences in short- and long-term trampling effects. Both short- and long-term trampling reduced plant cover, plant height and species density, though long-term effects were more pronounced than short-term effects. In both approaches, leaf litter biomass decreased, whereas soil density increased with trampling intensity. Other soil characteristics including soil moisture, total soil organic matter content and total organic nitrogen content were not or only marginally affected by short- and long-term trampling. Furthermore, soil microbial biomass and the activity of dehydrogenase did not change in both approaches. In contrast, the activity of b-glucosidase was only reduced by short-term trampling, whereas activity of phosphomonoesterase was reduced only by long-term trampling. Soil compaction was one factor reducing microbial activities at low and medium trampling intensities in our experiment and in the highly compacted area around the fire rings. We conclude that it could be problematic to use the results of short-term trampling experiments to predict general long-term trampling effects. Our results imply also that the restoration of degraded sites might be hampered by the low nutrient turnover resulting from the reduced litter layer and changes in enzyme activities, mitigating a successful re-establishment and growth of plants.

Keywords: fire places - long-term effects - outdoor recreation - short-term effects - soil enzyme activities - urban forest

2008  Past pasture management affects the land snail diversity in nutrient-poor calcareous grasslands — Boschi C & Baur B — Basic and Applied Ecology 9: 752–761   doi> 10.1016/j.baae.2007.09.006 

Changes in agriculture (intensification or abandonment) have resulted in a dramatical reduction of semi-natural grasslands in Central Europe in the 20th century. Recent management actions aim to restore overgrown and formerly fertilized nutrient-poor grasslands. Former land use is known to influence the present-day vegetation. Similar information is not available for animals with low dispersal ability. We investigated the effect of pasture management history over a period of 55 years on the present-day land snail diversity in 20 dry, nutrient-poor grasslands in the Swiss Jura mountains. Snails were recorded in pastures left unmanaged for 10-40 years but recently cleared from overgrowing shrubs, in pastures fertilized for 15-25 years but recently managed extensively (no fertilizer), and in pastures which have been extensively managed throughout (=control). Past shrub cover had a negative effect on the total number of snail species and the number of red-listed individuals. Former use of fertilizer reduced red-listed species and individuals and changed the snail community. Three species (Vitrina pellucida, Helicella itala and Abida secale) were found less frequently in formerly fertilized pastures than in extensive pastures. Our results show that changes in pasture use for a period of 10-40 years caused long-term alterations of the land snail fauna.

Keywords: land-use history - shrub cover - management intensity - fertilization - gastropods - biodiversity

2008  Parasitic mites influence fitness components of their host, the land snail Arianta arbustorum — Schüpbach HU & Baur B — Invertebrate Biology 127: 350–356   doi> 10.1111/j.1744-7410.2008.00138.x 

Parasites can influence the population dynamics of their hosts by affecting life-history strategies and behavior. The hematophageous mite Riccardoella limacum lives in the lung cavity of terrestrial gastropods. We used correlational and experimental approaches to investigate the influence of parasite infection on the behavior and life-history traits of the simultaneously hermaphroditic land snail Arianta arbustorum, a common host of R. limacum. Naturally infected individuals of A. arbustorum, collected in the wild, showed a decreased activity compared with uninfected snails. The reproductive output, expressed as the number of eggs deposited in a reproductive season, was reduced in mite-infected hosts. However, the hatching success of the eggs laid by parasitized snails was slightly higher than that of uninfected individuals. We also examined winter survival in 361 adults of A. arbustorum collected from four natural populations. The prevalence of mite infection ranged from 44.8% to 70.1% in three populations (snails in the fourth population were not infected). Winter survival was reduced in infected snails in two out of three populations. Furthermore, experimentally infected snails from an uninfected population showed a reduced winter survival compared with control snails. Our results indicate that parasite pressure imposed by members of R. limacum may influence life history in A. arbustorum.

Keywords: terrestrial gastropod - reproduction - survival - life history

2008  Effects of construction noise on behaviour of and exhibit use by Snow leopoards Uncia uncia at Basel zoo — Sulser CE, Steck BL & Baur B — International Zoo Yearbook 42: 199–205   doi> 10.1111/j.1748-1090.2007.00040.x 

Noise caused by human activities can cause stress in animals. We examined whether noise from construction sites affects the behaviour of and exhibit use by three Snow leopards Uncia uncia at Basel zoo. The behaviour and location of the animals were recorded at 1†minute intervals, using the instantaneous scan sampling method over a period of 216†hours (104†hours on noisy days and 112†hours on quiet days). The animals differed individually in their responses to the construction noise. On noisy days, the Snow leopards generally spent less time in locomotion and more time resting, but even on quiet days, resting was the predominant behaviour performed. Under noisy conditions, they increased social resting and decreased resting alone. Walking and social walking were also reduced on noisy days. Furthermore, the Snow leopards spent considerably more time in the remote off-exhibit enclosure under noisy conditions. Independent of background noise, they stayed more than half of the time in the caves and the forecourts of the outdoor enclosure. On quiet days, the Snow leopards used more sectors of their exhibit than on noisy days. The results indicate that the Snow leopards responded to construction noise by increasing the amount of time spent resting and by withdrawing to the remote parts of their exhibit.

Keywords: behaviour - caves - construction noise - exhibit use - resting - snow leopards

2008  Experimental evidence for a new transmission route in a parasitic mite and its mucus-dependent orientation towards the host snail — Schüpbach HU & Baur B — Parasitology 135: 1679–1684   doi> 10.1017/S0031182008005039 

The route of transmission and host finding behaviour are fundamental components of a parasite's fitness. Riccardoella limacum, a haematophagous mite, lives in the mantle cavity of helicid land snails. To date it has been assumed that this parasitic mite is transmitted during courtship and mating of the host. Here we present experimental evidence for a new transmission route in the host snail Arianta arbustorum. Parasite-free snails were kept on soil on which previously infected host snails had been maintained for 6 weeks. R. limacum was successfully transmitted via soil without physical contact among hosts in 10 out of 22 (45.5%) cases. In a series of experiments we also examined the off-host locomotion of R. limacum on snail mucus and control substrates using an automated camera system. Parasitic mites showed a preference to move on fresh mucus. Our results support the hypothesis that R. limacum uses mucus trails to locate new hosts. These findings should be considered in commercial snail farming and when examining the epidemiology of wild populations.

Keywords: parasite transmission - host-finding - snail mucus - Arianta arbustorum - Riccardoella limacum

2007  Fire place preferences of forest visitors in northwestern Switzerland: Implications for the management of picnic sites — Hegetschweiler KT, Rusterholz H-P & Baur B — Urban Forestry and Urban Greening 6: 73–81   doi> 10.1016/j.ufug.2007.03.001 

Some recreational activities in urban forests can cause extensive damage to soil and vegetation. In Switzerland, forest visitors frequently build fires outside picnic sites for barbecuing. This indicates that the existing picnic sites are either not attractive enough for these visitors, or that there are not enough sites for all the visitors during peak days. We used an on-site survey to assess the requirements of picnickers in two forest areas in the vicinity of Basle. Results showed that the existing picnic sites do not meet the requirements of some visitor groups, causing the respective visitors to make their own fires in locations that suit them better. There was a preference for sites near streams, away from forest roads and close to open spaces. Furthermore, while some visitors highly appreciated the well-equipped official sites, others preferred more natural infrastructure with pieces of stones forming a fire ring rather than concrete rims, and logs to sit on instead of benches. Picnic sites that are closer to the requirements of visitors who normally steer away from official sites might reduce the number of self-made fire rings. The study shows that understanding visitor behaviour is a prerequisite for the implementation of measures to reduce ecological impacts.

Keywords: day use - picnicking - recreational infrastructure - survey - urban forest - visitor monitoring

2007  Die Bedeutung der Erholungsnutzung des Waldes am Beispiel von Picknicken und Grillieren: Ergebnisse einer gesamtschweizerischen Umfrage bei Forstfachleuten und Waldeigentümern [The relevance of forest recreation exemplified by picnicking and grilling: Results of a nationwide survey aimed at forestry experts and public forest owners in Switzerland] — Hegetschweiler KT, Skorupinski A, Rusterholz H-P & Baur B — Schweizerische Zeitschrift für Forstwesen 158: 39–49
Artikel als pdf Datei herunterladen
(© Schweizerische Zeitung für das Forstwesen)

The recreational function of forests is highly relevant in urban areas. Picnicking and grilling are two of the most popular recreational activities in Swiss forests. While the density of official picnic sites with barbecue pits (number per ha) is similar in forests near large and small urban areas and in rural areas, the density of fire rings outside official picnic sites is especially high in forests that surround large urban areas. According to experts, the low concentration of barbecue pits and available firewood coupled with forest visitors seeking adventure and romanticism often lead to the creation of ´wildª fire rings. Recreational activities in the forest often lead to conflicts.Conflicts between recreation and hunting, in particular, seem to be pronounced in all areas of Switzerland. The disturbance of wildlife by recreationists is regarded as a major problem.In many places, direct and indirect management actions are implemented in order to reduce these conflicts.

Keywords: survey - forestry experts - outdoor recreation - picnicking - grilling -Switzerland

2007  Distribution and substrate preference of the invasive clam Corbicula fluminea in the river Rhine in the Region of Basel (Switzerland, Germany, France) — Schmidlin S & Baur B — Aquatic Sciences 69: 153–161   doi> 10.1007/s00027-006-0865-y 

The Asiatic clam Corbicula fluminea invaded the river Rhine in the Netherlands and Germany in the 1990s. It was first recorded in Switzerland (Basel) in 1995. We examined the distribution of the clam at 76 sites along the bank of the river Rhine, in three first order tributaries (Wiese, Birs, Ergolz) and in the Canal de Huningue in the region of Basel (Switzerland, Germany and France) in 2003. C. fluminea was found in the river Rhine and in the Canal de Huningue, which obtains water from the river Rhine. C. fluminea was recorded 22 km upstream of Basel, but not any further. This indicates a mean upstream spread of 2.4 km per year. It had not yet colonized any of the first order tributaries examined. The clam was most abundant on finegrained substrates (sand) with slowly flowing, shallow water. This finding was confirmed by a substrate choice experiment in the river Rhine. Our results show that the spread of C. fluminea in the river Rhine does not stop where cargo shipping ends. Passive dispersal by waterfowl and recreational boating may facilitate further upstream spread. C. fluminea might be less successful in colonizing rivers with rapid current such as first order tributaries. These are assumed to serve as refuges for native molluscs.

Keywords: asiatic clam - invasive species - range expansion - substrate choice

2007  Effect of cliff connectivity on the genetic population structure of a rock-dwelling land snail species with frequent self-fertilization — Armbruster GFJ, Hofer M & Baur B — Biochemical Systematics and Ecology 35: 325–333   doi> 10.1016/j.bse.2006.12.005 

To examine the effect of habitat connectivity on the genetic differentiation in the frequently selling gastropod Chondrina avenacea we assessed RAPD profiles in 12 subpopulations from continuous cliffs and in 12 subpopulations from small, naturally fragmented cliffs in the Swiss Jura mountains. Subpopulations of C. avenacea on continuous cliffs showed a smaller number of polymorphic RAPD loci and a lower gene diversity (Nei's h = 0.049) than subpopulations on fragmented cliffs (h = 0.078). Genetic distance was not correlated with geographical distance between subpopulations. GST analysis indicated strong isolation effects. Neither the number of polymorphic loci nor Nei's h was correlated with local population density. Our analysis indicates that the local population structure of C. avenacea is a combined result of frequent self-fertilization, genetic drift and low dispersal. Similar findings have been reported in studies on spatial population structure of plants. We suggest that future management actions (selective tree cutting, and controlled access of sport climbers) should also consider small, isolated limestone cliffs to preserve the genetic diversity of C. avenacea.

Keywords: habitat connectivity - fragmentation - limestone cliffs - gastropods - RAPD

2007  Effects of management intensity on land snails in Swiss nutrient-poor pastures — Boschi C & Baur B — Agriculture, Ecosystems & Environment 120: 243–249   doi> 10.1016/j.agee.2006.09.008 

The influence of management intensity on the richness, abundance and composition of land snail species was examined in 21 calcareous, nutrient-poor cattle pastures in the northwestern Jura mountains, Switzerland. Grazing intensity was positively correlated with the extent of fertilization of the pastures. Pastures without fertilizer application and with low grazing intensity harboured more snail species and more threatened snails than pastures with annual addition of manure or pastures with manure and nitrogen fertilizer and higher grazing intensity. Fewer snail individuals, open-land species and open-land individuals were found on pastures with high than on pastures with low management intensity. To preserve the threatened snail species in dry, nutrient-poor grasslands, a network of pastures should be managed without fertilization and grazing intensity should not exceed 180 LU.ha-1.d (product of livestock units per hectare and grazing days).

Keywords: pasture - fertilization - grazing intensity - gastropods - biodiversity

2007  The effect of horse, cattle and sheep grazing on the diversity and abundance of land snails in nutrient-poor calcareous grasslands — Boschi C & Baur B — Basic and Applied Ecology 8: 55–65   doi> 10.1016/j.baae.2006.02.003 

Livestock grazing is a common management practise in semi-natural grasslands in Central Europe. Different types of livestock (horses, cattle, sheep) and grazing intensity are known to affect the richness and composition of plant species. However, knowledge of grazing-dependent effects on invertebrates is limited. We examined the influence of horse, cattle and sheep grazing on the richness, abundance and composition of land snail species in 21 calcareous nutrient-poor grassland areas in the northwestern Jura Mountains, Switzerland. Grazing by different livestock species did not affect the species richness, abundance and species composition of land snails. Furthermore, the number of open-land species and the ratio of large- to small-sized snail species or individuals did not differ among the three pasture types. However, independent of livestock species, grazing intensity negatively influenced the snail fauna. Snail species richness, abundance and number of Red list species decreased with increasing grazing intensity. Grazing intensity also affected the occurrence of individual snail species (Truncatellina cylindrica, Cecilioides acicula, Candidula unifasciata and Trichia plebeia). To preserve the snail fauna in nutrient-poor grasslands, pastures can be stocked with horses, cattle or sheep. However, both maximum stocking rate (number of livestock units per hectare) and grazing duration (number of grazing days per year) must be carefully defined for the proper management of the pastures.

Keywords: pasture management - livestock species - grazing intensity - gastropods - Biodiversity

2007  Hafen- und Gewerbegebiete als Schwerpunkte pflanzlicher Diversität innerhalb urban-industrieller Ökosysteme – Botanische Bestandesaufnahme des Rheinhafengeländes Birsfelden, Schweiz — Lenzin H, Meier-Küpfer H, Schwegler S & Baur B — Naturschutz und Landschaftsplanung 39: 86–93

Auf seinen unterschiedlich genutzten Kies- und ungenutzten Lagerflächen beherbergt der 54 ha grosse Birsfelder Rheinhafen (Schweiz) insgesamt 230 Pflanzenarten, davon auch Populationen von 64 (28 %) regional oder national gefährdeten Spezies. Auf denselben Flächen wurden lediglich 36 (15,6 %) Neophyten festgestellt. Anhand der Untersuchungen im Birsfelder Hafen werden habitatspezifische Besonderheiten und deren Naturschutzproblematik diskutiert. Die Ergebnisse belegen die herausragende Bedeutung von extensiv und divers genutzten Hafen- und Gewerbegebieten innerhalb der ohnehin als artenreich geltenden urban-industriellen Ökosysteme und zeigen, dass diese schützenswerte Biodiversitäts-Hotspots darstellen können.

2007  Intensified grazing affects endemic plant and gastropod diversity in alpine grasslands of the Southern Carpathian mountains (Romania) — Baur B, Cremene C, Groza C, Schileyko AA, Baur A & Erhardt A — Biologia 62: 438–445   doi> 10.2478/s11756-007-0086-4 

Alpine grasslands in the Southern Carpathian Mts, Romania, harbour an extraordinarily high diversity of plants and invertebrates, including Carpathic endemics. In the past decades, intensive sheep grazing has caused a dramatic decrease in biodiversity and even led to eroded soils at many places in the Carpathians. Because of limited food resources, sheep are increasingly forced to graze on steep slopes, which were formerly not grazed by livestock and are considered as local biodiversity hotspots. We examined species richness, abundance and number of endemic vascular plants and terrestrial gastropods on steep slopes that were either grazed by sheep or ungrazed by livestock in two areas of the Southern Carpathians. On calcareous soils in the Bucegi Mts, a total of 177 vascular plant and 19 gastropod species were recorded. Twelve plant species (6.8%) and three gastropod species (15.8%) were endemic to the Carpathians. Grazed sites had lower plant and gastropod species richness than ungrazed sites. Furthermore, grazed sites harboured fewer gastropod species endemic to the Carpathians than ungrazed sites. On acid soils in the Fagaras Mts, a total of 96 vascular plant and nine gastropod species were found. In this mountain area, however, grazed and ungrazed sites did not differ in species richness, abundance and number of endemic plant and gastropod species. Our findings confirm the high biodiversity of grasslands on steep slopes in the Southern Carpathian Mts and caution against increasing grazing pressure in these refuges for relic plants and gastropods as well as for other invertebrates.

Keywords: Alpine grassland - biodiversity - Bucegi Mts - Gastropoda - grazing - Fagaras Mts - vascular plants

2007  Polymorphic microsatellite DNA markers in the endangered land snail, Trichia caelata (Gastropoda, Stylommatophora) — Armbruster GFJ, Alvarez C, Pesaro M & Baur B — Molecular Ecology Notes 7: 1123–1124   doi> 10.1111/j.1471-8286.2007.01801.x 

Eight novel polymorphic microsatellite loci are presented for the endangered land snail Trichia caelata, a rare species endemic to the Northwestern Jura mountains, Switzerland. The number of alleles per locus ranged from six to 17. At seven loci, the expected heterozygosity differed significantly from observed heterozygosity. No evidence for linkage disequilibrium was detected between locus pairs. We are currently using these markers to investigate the genetic population structure of T. caelata in its restricted distribution area.

Keywords: Helicidae - Jura mountains - microsatellites - terrestrial gastropod -Trichia

2007  Effect of rock climbing on the calcicolous lichen community of limestone cliffs in the northern Swiss Jura Mountains — Baur B, Fröberg L & Müller SW — Nova Hedwigia 85: 429–444   doi> 10.1127/0029-5035/2007/0085-0429 

Exposed limestone cliffs in the Swiss Jura Mountains harbour a diverse lichen community with some rare species. Sport climbing has recently increased in popularity on these cliffs. We examined the effect of sport climbing on calcicolous lichens by assessing species diversity and cover of lichens in climbed and unclimbed areas of 10 isolated cliffs in the northern Swiss Jura Mountains. We also investigated possible associations between lichens and lichen-feeding land snails on these cliffs. A total of 38 calcicolous lichen species, three bryophytes and one alga were found on the rock faces of 10 cliffs. Twenty lichen species (52.6%) were epilithic, 16(42.1%) endolithic and two (5.3%) foliose. Overall, the epilithic lichen species covered 8.3% of the rock surface, endolithic species 10.2%, and foliose species 0.03%. Climbed and unclimbed rock areas did not differ in total number of lichen species, species density (number of species per 100 cm ²) or total lichen cover. However, the frequency of occurrence of epilithic lichens was lower along climbing routes than in unclimbed areas. A multi-response permutation test showed that the lichen community composition of climbed areas differed from that of unclimbed areas. The dissimilarity of lichen communities between climbed and unclimbed areas increased with increasing climbing intensity on the focal route in climbed areas, but not with the age of the climbing route. Five of the 11 snail species recorded on the cliff faces were specialized lichen feeders. Plots along climbing routes harboured fewer snail species than plots in unclimbed areas. Total snail abundance was positively correlated with lichen species richness, but no correlation between snail species richness and lichen species richness was found. Our results indicate that frequent rock climbing can change the lichen community and reduce the snail community of limestone cliffs. A climbing-related reduction of snail abundance may also alter the lichen-herbivore interaction and indirectly change competitive interactions among lichen species.

Keywords: disturbance - Jura mountains - lichen - gastropod - rock climbing; - limestone cliff

2006  Among- and within-population variation in sperm quality in the simultaneously hermaphroditic land snail Arianta arbustorum — Minoretti N & Baur B — Behavioral Ecology and Sociobiology 60: 270–280   doi> 10.1007/s00265-006-0165-5 

Sperm competition models on the evolution of sperm size assume associations with another sperm quality trait, sperm longevity. Sperm length can also provide an indication of possible mechanisms affecting motility and thus fertilization success. Despite their importance, however, detailed mechanisms of sperm competition at the gamete level are poorly understood. In simultaneously hermaphroditic land snails, sperm traits and cryptic female choice are assumed to be crucial in determining fertilization success. We examined the variation in sperm length and number among individuals from four natural populations of the land snail Arianta arbustorum, a species with multiple mating and long-term sperm storage. We also assessed variation in velocity, motility and longevity of sperm in snails from two of the four populations. Independent of shell size, sperm length differed among populations and, to a minor extent, even among individuals within populations. Mean sperm length of a snail was not correlated with the number of sperm delivered in a spermatophore. The mean sperm velocity (=VCL) did not differ between snails from two populations. However, VCL varied among snails. Percentage motility and longevity of sperm differed between snails from the two populations. No correlations were found between length, velocity, percentage motility and longevity of sperm. To conclude, individual snails differed in sperm quality, and this variation may partly explain the differential fertilization success between A. arbustorum snails. Moreover, our findings did not support the positive association between sperm length and longevity assumed by sperm competition models for internally fertilizing species.

Keywords: sperm length - sperm longevity - sperm velocity - sperm number - sperm competition

2006  Bursa tract diverticulum in the hermaphroditic land snail Arianta arbustorum (Stylommatophora: Helicidae): Morphology, function, and evolutionary implications — Beese K, Beier K & Baur B — Journal of Morphology 267: 940–953   doi> 10.1002/jmor.10451 

A bursa tract diverticulum is widespread in the female part of the hermaphroditic reproductive system of stylommatophoran pulmonates. However, the ultrastructure of the diverticulum is unknown and there is only anecdotal evidence for a spermatophore-dissolving function for this organ. In the present study, we examined the ultrastructure of the diverticulum and investigated histological, histochemical and morphometric changes at different time intervals after mating in the simultaneously hermaphroditic land snail Arianta arbustorum. The diverticulum in this species of snail is a prominent organ, consisting of a luminal columnar epithelium surrounded by a thick layer of connective tissue. During mating, the diverticulum functions as the site of spermatophore uptake. Within the lumen of the diverticulum, the spermatophore wall is dissolved or at least partly broken down. The digested material is taken up by epithelial cells and accumulated in molluscan-specific cells of the connective tissue, the so-called rhogocytes. Subsequent to copulation, the total diameter of the diverticulum increases markedly, reaching a maximum size 12 hours after mating, while at the same time the thicknesses of the diverticulum wall and diverticulum epithelium decrease. The length of the diverticulum shows a positive allometry and a high phenotypic variation compared to snail size, which suggests that the diverticulum is under directional sexual selection. We propose that the diverticulum in A. arbustorum has evolved in response to selection pressures imposed by divergent evolutionary interests between male and female function.

Keywords: diverticulum - sexual conflict - sexual selection - sperm digestion - spermatophore

2006  Coevolution of male and female reproductive traits in a simultaneously hermaphroditic land snail — Beese K, Beier K & Baur B — Journal of Evolutionary Biology 19: 410–418   doi> 10.1111/j.1420-9101.2005.01022.x 

Inter- and intraspecific studies in gonochoristic animals reveal a covariation between sperm characteristics and the size of the female reproductive tract, indicating a rapid evolutionary divergence, which is consistent with the theory of post-copulatory sexual selection. Simultaneous hermaphrodites differ from species with separate sexes (gonochorists) in that they possess both functional male and female reproductive organs at the same time. We investigated whether in hermaphroditic animals intraspecific variation in reproductive traits results from divergent coevolution, by quantifying the variation in male and female traits among six natural populations of the snail Arianta arbustorum and examining the covariation in interacting traits. There was a significant among-population variation in spermatophore volume, number of sperm transferred and sperm length, as well as in volume of the sperm storage organ (spermatheca) and number of tubules, but not in spermatheca length. We found a positive association between sperm number transferred and spermatheca volume. This result suggests that the same post-copulatory mechanisms as in gonochorists drive the correlated evolution of reproductive characters in hermaphrodites.

Keywords: cryptic female choice - genital divergence - sexual conflict - simultaneous hermaphrodite - sperm competition - sperm storage organ

2006  Effects of abandonment of subalpine hay meadows on plant and invertebrate diversity in Transylvania, Romania — Baur B, Cremene C, Groza G, Rakosy L, Schileyko AA, Baur A, Stoll P & Erhardt A — Biological Conservation 132: 261–273   doi> 10.1016/j.biocon.2006.04.018 

Recent changes in agriculture (intensification or abandonment) have resulted in a critical reduction of semi-natural grasslands in Eastern Europe. Subalpine semi-natural grasslands in Transylvania, Romania, harbour a high diversity of plants and invertebrates, including endemics, and are considered refugia for numerous threatened open-land species. We investigated effects of land abandonment by examining species richness, species abundance, proportion of open-land, endemic and threatened vascular plants, gastropods, and diurnal and nocturnal Lepidoptera in extensive hay meadows (initial stage), and three seral stages of succession (early stage of abandoned hay meadow, naturally growing birch forest, and mature forest) in the mountainous region of Baisoara in Transylvania. A total of 626 species (225 vascular plants, 16 gastropods, 68 diurnal and 317 nocturnal Lepidoptera) were found in the 16 study sites (four replicates per successional stage). The four taxonomic groups differed in their response to the abandonment of hay meadows. Each stage of succession harboured the maximum species richness for one taxonomic group: extensive hay meadows for vascular plants, abandoned hay meadows for diurnal Lepidoptera, birch forests for nocturnal Lepidoptera, and mature forests for gastropods. In all four taxonomic groups the complementarity of species composition increased with successional age, whereas the number of characteristic open-land species decreased with successional age. The four successional stages did not differ in proportion of red-listed plant and diurnal Lepidoptera species. In nocturnal Lepidoptera, however, the proportion of red-listed species increased with successional age. Furthermore, successional stages did not differ in number of plant species endemic to the Carpathians and Eastern Europe. Our results indicate the high conservation value of all stages of subalpine grassland succession for the indigenous biodiversity of Transylvania. To prevent losses of characteristic species, we suggest a rotational grassland management program that maintains different successional stages.

Keywords: land use change - grassland succession - Carpathic endemic - Eastern Europe

2006  Effects of forestry practices on relict plant species on limestone cliffs in the northern Swiss Jura mountains — Müller SW, Rusterholz H-P & Baur B — Forest Ecology and Management 237: 227–236   doi> 10.1016/j.foreco.2006.09.048 

Limestone cliffs in the forests of the Swiss Jura mountains harbour a highly diverse plant community including glacial relict species. This unique cliff vegetation is increasingly threatened by overgrowing forest and recreational activities (sport climbing and picnicking). Management objectives of the surrounding forest focus on the conservation of the cliff vegetation. The most suitable forestry practice to achieve this goal is, however, still unknown. We examined the effects of two different forestry practices (clear-cutting and shelter tree cutting) on the species richness and abundance of vascular plants on the face, at the base and on the talus of three cliffs. As controls we considered areas with no management in the past 80 years (forest reserves) at the same cliffs. Plant species density (number of species/m²) and vegetation cover were higher in shelter cut areas than in the forest reserves both on the talus and at the cliff base. Clear-cut areas had a higher vegetation cover than forest reserves on the talus. Shelter cut areas showed a larger proportion of plants with high light demand and a higher mean light score of plants than clear-cut areas and forest reserves. We conclude that selective cutting of trees (shelter tree cutting) is the best forestry practice for the conservation of a high biodiversity and a multitude of relict plant species on limestone cliffs in the Jura mountains. However, this forestry practice is time-consuming and thus expensive. To preserve the specialised cliff flora, sponsorship for this forestry practice is needed from governmental and non-governmental organisations.

Keywords: cliff ecology - light conditions - beech forests - plant conservation

2006  Expandable spermatheca influences sperm storage in the simultaneously hermaphroditic snail Arianta arbustorum — Beese K & Baur B — Invertebrate Reproduction and Development 49: 93–101
Artikel als pdf Datei herunterladen

In many simultaneously hermaphroditic land snail species the sperm storage organ (spermatheca) is highly structured, suggesting that the female function might be able to influence offspring paternity. Physical properties of the sperm storage organ, including its initial size and sperm storage capacity may also affect fertilization patterns in multiply mated snails. We examined the structure, volume and tubule length of empty spermathecae in the land snail Arianta arbustorum and assessed differences in spermatheca size following a single copulation. The number of spermathecal tubules ranged from 2-7, but was not correlated with the volume of empty spermathecae. The volume of sperm stored in the spermatheca after a copulation was correlated with neither the number of spermathecal tubules nor copulation duration. Mean spermathecal volume more than doubled between two and thirty six hours after sperm uptake, but the length of spermathecal tubules did not change. Interestingly, the volume of sperm stored in the spermatheca seems not to be related to the size of the spermatophore and thus not to the number of sperm received (= allosperm). The amount of allosperm digested in the bursa copulatrix was highly variable and no significant relationship with the size of the spermatophore received was found. These findings suggest that numerical aspects of sperm transfer are less important in influencing fertilization success of sperm in A. arbustorum than properties of the female reproductive tract of the sperm receiver.

Keywords: Arianta arbustorum - sexual selection - simultaneous hermaphrodite - sperm storage - spermathecal morphology

2006  Experimental habitat fragmentation and invertebrate grazing in a herbaceous grassland species — Stoll P, Dolt C, Goverde M & Baur B — Basic and Applied Ecology 7: 307–319   doi> 10.1016/j.baae.2005.09.001 

A field experiment was conducted to examine the effects of habitat fragmentation on herbivore damage to individually tagged leaves of Betonica officinalis rosettes. Fragments of different size and corresponding control plots were established at three study sites in nutrient-poor calcareous grasslands in the northern Swiss Jura mountains. Leaf damage was recorded three times over the growing season (late spring, summer and early autumn). Five years after the initiation of the fragmentation, the density of rosettes did not differ between fragments and control plots. The number of leaves per rosette was higher in fragments than in control plots in summer but not in late spring and early autumn. The extent of leaf damage, expressed as proportion of leaf area removed by invertebrate herbivores, increased over the vegetation period. Leaf damage was greater in fragments than in control plots at two study sites, whereas the opposite (less strongly expressed) was found at the third site. Number of species and density (individuals per m²) of potential herbivores (gastropods and grasshoppers) were recorded in all fragments and control plots. Effects of fragmentation on the number of species and densities depended on plot size and differed between gastropods and grasshoppers. Leaf damage in fragments increased with increasing density of gastropods if the third site, which had lowest leaf damage, was excluded. Such a positive relationship was neither found in control plots nor for grasshopper densities. Thus, movement of gastropods in fragments was probably restricted which resulted in increased feeding pressure at least in two sites. However, even if our fragmentation experiment was well designed and replicated, the interpretation of these experimental results remains difficult because there was large site-to-site and seasonal variation.

Keywords: Betonica officinalis - gastropods - grasshoppers - herbivory - invertebrates

2006  Field study on the regenerative capacity of three calcicolous lichen species damaged by snail grazing — Fröberg L, Baur A & Baur B — Lichenologist 38: 491–493   doi> 10.1017/S0024282906005469 

Lichen growth and regeneration depend on the net photosynthetic production, the lateral allocation of products, on abiotic factors, competition and herbivory, and may therefore vary both in space and time (Hill 1981). Herbivores cause different damage to lichens in response to different thallus structure (surface toughness) and growth form, presence/absence of secondary compounds, and due to herbivore-specific differences in feeding (Lawrey 1984; Fröberg et al. 1993; Baur et al. 1994; Hesbacher et al. 1995). Regeneration of artificially damaged lichen tissue has been investigated in detail, for example in Xanthoria parietina (L.) Th. Fr. (Honegger 1996; Honegger et al. 1996). However, quantitative assessments of the regenerative capacity of thalli damaged by herbivores are so far lacking. Damage to lichens by grazing gastropods is made by highly specialized radulae and can therefore not be imitated by any mechanical treatment (Baur et al. 2000). Herbivory by snails also involves the production of saliva and mucus, which both could affect lichen regeneration.

2006  Small-scale experimental habitat fragmentation reduces colonization rates in species-rich grasslands — Joshi J, Stoll P, Rusterholz H-P, Schmid B, Dolt C & Baur B — Oecologia 148: 144–152   doi> 10.1007/s00442-005-0341-8 

Habitat fragmentation is one of the most important threats to biodiversity. Decreasing patch size may lead to a reduction in the size of populations and to an increased extinction risk of remnant populations. Furthermore, colonization rates may be reduced in isolated patches. To investigate the effects of isolation and patch size on extinction and colonization rates of plant species, calcareous grasslands at three sites in the Swiss Jura Mountains were experimentally fragmented into patches of 0.25, 2.25, and 20.25 m² by frequent mowing of the surrounding area from 1993 to 1999. Species richness in the fragment plots and adjacent control plots of the same sizes was recorded during these 7 years. In agreement with the theory of island biogeography, colonization rate was reduced by 30% in fragments versus non-isolated controls, and extinction increased in small versus large plots. Habitat specialists, in contrast to generalists, were less likely to invade fragments. In the last 4 years of the experiment, extinction rates tended to be higher in fragment than in control plots at two of the three sites. Despite reduced colonization rates and a tendency of increased extinction rates in fragments, fragmented plots had only marginally fewer species than control plots after 7 years. Hence, rates were a more sensitive measure for community change than changes in species richness per se. From a conservation point of view, the detected reduced colonization rates are particularly problematic in small fragments, which are more likely to suffer from high extinction rates in the long run.

Keywords: extinction - fragment size - generalists/specialists - interaction stochasticity - species turnover

2005  Alterations of steppe-like grasslands in Eastern Europe: a threat to regional biodiversity hotspots — Cremene C, Groza G, Rakosy L, Schileyko AA, Baur A, Erhardt A & Baur B — Conservation Biology 19: 1606–1618   doi> 10.1111/j.1523-1739.2005.00084.x 

Recent changes in agriculture (intensification or abandonment) have resulted in a critical reduction of steppe-like grasslands in Eastern Europe. These grasslands harbor an extraordinarily high diversity of plants and invertebrates, including endemics, and are considered refugia for numerous threatened open-land species. We examined species richness, and abundance, proportion of open-land, endemic and threatened vascular plants, gastropods, and diurnal and nocturnal Lepidoptera in six different vegetation types all originating from steppe-like grasslands in Transylvania, Romania. Vegetation types included extensively grazed pastures (initial stage), three seral stages of succession (early stage of abandoned grassland, abandoned grassland with shrubs, and mature forest), and two human-made grassland alterations, namely abandoned vineyards and Pinus plantations. A total of 852 species (291 vascular plants, 24 gastropods, 129 diurnal and 408 nocturnal Lepidoptera) were found in the 22 study sites. The four taxonomic groups differed in their response to the abandonment of steppe-like grassland, except that species richness of plants and diurnal Lepidoptera were positively correlated. The complementarity of species composition increased with successional age in all taxonomic groups examined. The number of characteristic open-land species decreased with successional age in plants and gastropods. All investigated vegetation types harbored threatened (red-listed) species. Endemic species were found in all vegetation types except mature forests and Pinus plantations. All Transylvanian endemics and the majority of threatened species found were open-land species. Extensively cultivated vineyards, which have been abandoned for two to three decades, also maintained high plant and invertebrate diversities, comparable to those of the corresponding stages of grassland succession. In contrast, Pinus plantations (a recent grassland alteration) have changed habitat quality and will have a devastating effect on the unique, indigenous diversity of these steppe-like grasslands as soon as the canopy closes. To prevent losses of characteristic species, we suggest a rotational grassland management program that maintains different seral stages. Succession to mature forest and additional Pinus plantations should be prevented.

Keywords: diurnal Lepidoptera - nocturnal Lepidoptera - endemic species - extinction - gastropods - habitat alteration - red-data species - succession - vascular plants

2005  Dispersal of the endangered flightless beetle Dorcadion fuliginator (Coleoptera: Cerambycidae) in spatially realistic landscapes — Baur B, Coray A, Minoretti N & Zschokke S — Biological Conservation 124: 49–61   doi> 10.1016/j.biocon.2004.12.011 

Habitat destruction and degradation are the major causes for the decline of the endangered grass-feeding beetle Dorcadion fuliginator in Central Europe. In the southern part of the Upper Rhine valley (border region of Switzerland, Germany and France) the habitat suitable for this flightless beetle has been reduced to small remnants of extensively managed dry grassland, usually surrounded by intensively cultivated agricultural fields or settlements. Using a mark-release-resight technique we examined movement patterns in three D. fuliginator populations to obtain basic information on the dispersal ability and longevity of this beetle. Estimated daily survival rates ranged from 88.8 to 90.8% in the populations examined. This corresponds to a mean life span of 10.5 days. Distances moved by D. fuliginator differed among populations. The beetles walked the largest distances in the verges of a field track. Several beetles moved distances of 20-100 m along the track, with a maximum distance of 218 m (a male in 12 days). The shortest displacements were recorded in the bank of the river Rhine, a narrow habitat surrounded by tarmac roads. We also assessed the spatial arrangement of 12 patches with D. fuliginator populations in two regions and estimated the size of each population over 4 years. Data on dispersal, daily survival, population size and spatial arrangement of patches were used to simulate patch-specific migration rates. The simulations suggested that in both areas the beetles regularly moved between neighbouring patches separated by distances shorter than 100 m, whereas patches separated by distances exceeding 500 m are isolated.

Keywords: connectivity - extinction - habitat degradation - isolation - management plan - spatially explicit dispersal model

2005  Disturbance of suburban Fagus forests by recreational activities: Effects on soil characteristics, above-ground vegetation and seed bank — Amrein D, Rusterholz H-P & Baur B — Applied Vegetation Science 8: 175–182   doi> 10.1658/1402-2001(2005)008[0175:DOSFFB]2.0.CO;2 

Questions: How does recreational disturbance (human trampling) affect soil characteristics, the performance of the understorey vegetation, and the density and species composition of the soil seed bank in Fagus sylvatica forests?
Location: Suburban forests near Basel, northwestern Switzerland.
Methods: We compared various soil characteristics and the performance of the understorey vegetation in six beech forest areas frequently disturbed by recreational activities with those in six undisturbed control areas, in spring 2003. In the same forest areas, the soil seed bank was investigated using the seedling emergence method. Samples were obtained from soil cores in January 2003.
Results: We found substantial changes in soil compaction, above-ground vegetation and in the soil seed bank due to recreational activities. In frequently visited areas, soil compaction was enhanced which caused a decrease in cover, height and species richness of both herb and shrub layers. Compared with control areas, the number of trampling-tolerant species of the seed bank was significantly higher in disturbed areas, and total species richness tended to be higher in disturbed than in control areas. Furthermore, the similarity in species composition between the above-ground vegetation and seed bank was significant lower in disturbed than in control areas.
Conclusions: The intensive use of suburban forests for recreational activities, mainly picnicking, affects the vegetation of natural beech forests. Our study indicates that a restoration of degraded forest areas from the soil seed bank would result in a substantial change of the vegetation composition.

Keywords: deciduous forest - human trampling - picnic site - restoration - soil compaction - species composition

2005  Effects of experimental small-scale habitat fragmentation on above-and below-ground plant biomass in calcareous grasslands — Dolt C, Goverde M & Baur B — Acta Oecologica 27: 49–56   doi> 10.1016/j.actao.2004.09.002 

The effect of small-scale fragmentation on the above-ground plant biomass was examined in nutrient-poor calcareous grasslands in the northern Swiss Jura mountains in three successive years. In the same field experiment, the fragmentation effect on the below-ground plant biomass was evaluated in 1 year. Additionally, species richness and abundance of plants were recorded. The experimental set-up consisted of 12 blocks with 48 fragments (24 small, 12 medium and 12 large) and 48 corresponding control plots distributed over three study sites. Fragmentation was maintained by frequently mowing the area between the fragments. Three to 5 years after the beginning of the experiment, plant biomass was harvested in all fragments and control plots in late autumn every year. In general, fragments contained more above- and below-ground plant biomass than control plots. The increase in above-ground plant biomass was partly due to an increased density of plants, and partly due to a change in species composition in fragments. In particular, a competitive shift of dominance towards tall grasses and forbs at the expense of smaller forbs was observed. Beside the main fragmentation effect on above-ground plant biomass, interactive effects with year of investigation, study site and plot size were found. This indicates that the observed fragmentation effect is a combined result of various factors acting to a different extent at different sites and plot sizes. The fragmentation-related increase in plant productivity could affect higher trophic levels such as herbivore and predator communities.

Keywords: above ground plant part - biological productivity - biodiversity - calcareous soils - grassland - biomass - below ground plant part - fragmentation - habitat - experimental study

2005  Experimental small-scale grassland fragmentation alters competitive interactions among ant species — Braschler B & Baur B — Oecologia 143: 291–300   doi> 10.1007/s00442-004-1778-x 

Different species may respond differently to habitat fragmentation. Theory predicts that abundant generalist species should be less affected by fragmentation than specialist species. In ant communities, the most abundant species is often behaviourally dominant. Thus, habitat fragmentation could alter competitive interactions between the dominant ant species and the other species. We tested this hypothesis in a long-term grassland fragmentation experiment. Fragments of different size (20.25 and 2.25 m²) were isolated by a 5-m wide strip of frequently mown vegetation. Control plots were situated in adjacent undisturbed grassland. Ant density and species composition were assessed 3 and 6 years after initiation of the experimental fragmentation. The effect of the dominant ant species on the resource use of the other species was examined at natural sugar resources (aphids and extrafloral nectaries) and at artificial sugar baits. Lasius paralienus was the most abundant ant species (72% of nests) in the grasslands examined. Species richness and forager density in the other species decreased with increasing density of L. paralienus in fragments but not in control plots. The overall forager density of the other species was positively related to their habitat niche overlap with L. paralienus. The density of foragers of the other species at sugar resources was not affected by L. paralienus forager density. The experimental fragmentation resulted in an increase in natural sugar resources in fragments. This may have reduced the intensity of interspecific competition for sugar resources. Our study shows that the grassland fragmentation altered interactions between the dominant L. paralienus and the other ant species.

Keywords: community composition - dominance - Euphorbia cyparissias - Formicidae - nest density

2005  Foot mucus and periostracum fraction as non-destructive source of DNA in the land snail Arianta arbustorum, and the development of new microsatellite loci — Armbruster GFJ, Koller B & Baur B — Conservation Genetics 6: 313–316   doi> 10.1007/s10592-004-7823-9 

Feathers, hair, egg membranes, bones, urine and faeces have all been utilized as non-invasive sources of DNA in vertebrate studies. In insects, exuviae and caterpillar frass can serve as non-destructive DNA source. Similar non-invasive sources of DNA are not yet available for endangered and rare molluscs. In this note, we report on two novel, nondestructive methods of DNA isolation in the land snail Arianta arbustorum (L.), and present nine novel microsatellite loci since previously published loci yielded a complete lack of heterozygosity.

Keywords: DNA isolation - fingerprinting - gastropods - non-invasive genetics

2005  Interpopulation variation in the prevalence and intensity of parasitic mite infection in the land snail Arianta arbustorum — Baur A & Baur B — Invertebrate Biology 124: 194–201   doi> 10.1111/j.1744-7410.2005.00019.x 

The parasitic mite Riccardoella limacum sucks blood in the lung of its host, the land snail Arianta arbustorum. The infection of various host populations was examined in Switzerland. In a lowland snail population, prevalence of infection did not vary among seasons. However, intensity of mite infection in dissected individuals of A. arbustorum was high in autumn, but low in winter and spring when <= 100 mite eggs were found attached to the lung epithelium. A novel, non-invasive parasite screening method was used to estimate the number of mites on living host snails. An analysis of repeatability revealed that 92.9% of the snails were correctly classified as infected or non-infected with this non-invasive method. Prevalence of mite infection was examined in 997 adults of A. arbustorum from 11 natural populations distributed over an altitudinal gradient ranging 335-2360 m. No infected snails were found in 7 populations, while in the remaining 4 populations the prevalence of mite infection ranged 45.8-77.8%. Intensity of infection also differed among the 4 host populations. No geographic pattern in prevalence of infection was found. However, parasitic mites did not occur in snail populations situated at elevations of 1290 m or higher. A possible explanation for this finding could be that the host's hibernation period may be too long at high elevations for mites and their eggs to survive. At low elevations, other factors may affect the presence of R. limacum in the lung of A. arbustorum.

Keywords: terrestrial gastropod - mite - lung parasite - geographic variation - seasonal variation

2004  Effects of protein and calcium concentrations of artificial diets on the growth and survival of the land snail Arianta arbustorum — Wacker A & Baur B — Invertebrate Reproduction and Development 46: 47–53

Animals depend on a large set of essential compounds in their food. However, not all units of food are equal from a nutritional point of view. A reduced supply of protein and calcium might be critical for the growth, reproduction and survival of herbivorous gastropods. We experimentally examined the effects of different protein and calcium supplies on the growth and survival of the land snail Arianta arbustorum. Groups of snails were reared on agar-based diets with each of three levels of protein and calcium (nine treatments). Snails fed a high-protein diet grew faster and reached adulthood earlier and at a larger adult size than snails fed intermediate and low-protein diets. Surprisingly, the calcium concentration did not affect shell growth and adult size. Snails reared on intermediate- and low-calcium diets increased their consumption rates, but, despite this compensatory feeding, these snails were unable to take up the amount of calcium required for metabolism and shell growth and had a higher mortality. The calcium deficiency could partly be mitigated by the snails' internal calcium storage and reallocation capacity. A depletion of internal calcium reserves adversely affects the entire nutrient metabolism and was the probable cause for the high mortality rates associated with the intermediate- and low calcium diets observed in the present study.

Keywords: calcium deficiency - food quality - gastropod - optimal diet - protein deficiency

2004  Effects of rock climbing on plant communities on exposed limestone cliffs in the Swiss Jura mountains — Rusterholz H-P, Müller SW & Baur B — Applied Vegetation Science 7: 35–40   doi> 10.1658/1402-2001(2004)007[0035:EORCOP]2.0.CO;2 

Exposed cliffs of the Swiss Jura mountains harbour a highly diverse flora with many rare and endangered plant species. Many cliffs are frequently visited by rock climbers. We examined the impact of rock climbing on vascular plants in the lower part of four cliffs of the Gerstelflue (NW Switzerland) by comparing the vegetation of climbed and unclimbed areas. In climbed areas plant cover and species density were reduced. Similarly, the density of forbs and shrubs decreased, whereas the density of ferns tended to increase. In addition, rock climbing caused a significant shift in plant species composition and altered the proportions of different plant life forms. Rock climbing can be a threat to sensitive plants of the limestone cliff community.

Keywords: disturbance - Switzerland - vascular plants

2004  Grain-dependent relationships between plant productivity and invertebrate species richness and biomass — Braschler B, Zschokke S, Dolt C, Thommen GH, Oggier P & Baur B — Basic and Applied Ecology 5: 15–24   doi> 10.1078/1439-1791-00184 

The relationships among productivity, species richness and consumer biomass are of fundamental importance for understanding determinants of biodiversity. These relationships may depend on grain size. We examined the relationships between productivity (above-ground phytomass) and plant species richness and between productivity and species richness and biomass of gastropods and grasshoppers using sampling units of different sizes (0.5, 2.75 and 23 m²) in nutrient-poor, calcareous grasslands in north-western Switzerland in two successive years. Species richness of forbs had a unimodal relationship with productivity in sampling units of 0.5 m² and was negatively correlated with productivity at the other two plot sizes in one year. In the other year, forb species richness tended to decrease with productivity in sampling units of 23 m². No similar relationship was found for grasses. Gastropod biomass had a unimodal relationship with productivity at 0.5 m² in the first year. Grasshopper species richness was correlated with forb species richness at plot sizes of 2.75 and 23 m². This study demonstrates that patterns detected between productivity and diversity and between productivity and biomass of consumers depend on the grain size used in the investigation and vary among years.

Keywords: biodiversity - grasshoppers - terrestrial gastropods - above-ground plant biomass - Swiss Jura mountains

2004  Rock climbing alters the vegetation of limestone cliffs in the northern Swiss Jura Mountains — Müller SW, Rusterholz H-P & Baur B — Canandian Journal of Botany 82: 862–870   doi> 10.1139/b04-058 

Exposed cliffs in the northern Swiss Jura Mountains harbour a highly diverse flora with numerous endangered and relic plant species. On these cliffs, sport climbing is enjoying increasing popularity. We examined the ecological effects of sport climbing on vascular plants at the cliff base and on the cliff face by assessing plant cover and species density at various distances from frequently used climbing routes. Plant cover was significantly reduced at the base of climbing routes. Furthermore, species density (number of species per square metre) at the cliff base, as well as plant cover and species density at the cliff face, tended to increase with distance from the route. We also compared the vegetation of five frequently climbed cliffs with that of seven unclimbed cliffs. Climbing significantly altered the plant composition. Specialized rock species occurred less frequently on climbed cliffs than on unclimbed cliffs. Management plans and conservation actions are needed to preserve the threatened plant species on frequently climbed cliffs. Such plans should include the establishment of climbing-free protection areas on cliffs with a high number of specialized, relic plants and the protection of entire cliffs that are not yet climbed.

Keywords: disturbance - vegetation - Jura Mountains - rock climbing - limestone cliff

2003  Effects of experimental small-scale grassland fragmentation on spatial distribution, density and persistence of ant nests — Braschler B & Baur B — Ecological Entomology 28: 651–658   doi> 10.1111/j.1365-2311.2003.00549.x 

1. Grassland fragmentation is expected to influence the abundance of different invertebrate species to a different extent. Fragmentation-related effects are of particular importance in species that interact with many other species.
2. The density and spatial distribution of nests of 15 ant species in experimentally fragmented calcareous grasslands at three sites in the Northern Swiss Jura mountains were examined. Fragments of different size (0.25 m²), 2.25 m²), and 20.25 m²) were isolated by a 5-m wide strip of frequently mown vegetation. Control plots of corresponding size were situated in adjacent undisturbed grassland.
3. Three years after initiation of the experiment, ant nest density did not differ between fragments and control plots. Six years after initiation of the experiment, however, ant nest density and forager abundance were higher in large fragments than in large control plots. Ant nests tended to occur more frequently along the edge of fragments than in the core area. Persistence time of nests of the most abundant species, Lasius paralienus, tended to be shorter in fragments than in control plots. Furthermore, persistence time was longer in nests situated close to the fragment edge than in nests in the core area.
4. Effects on nest density, edge effects on the spatial distribution of nests, and the relationships between nest density and environmental factors were more pronounced when only nests of L. paralienus were considered. The implications of these findings for plant and other invertebrate species are discussed.

Keywords: abiotic factors - ants (Hymenoptera: Formicidae) - calcareous grasslands - density - habitat fragmentation - nest dispersion - nest persistence

2003  Experimental small-scale grassland fragmentation alters aphid population dynamics — Braschler B, Lampel G & Baur B — Oikos 100: 581–591   doi> 10.1034/j.1600-0706.2003.12220.x 
Artikel als pdf Datei herunterladen

Theory predicts that at higher trophic levels species are especially vulnerable to habitat fragmentation due to small population size and dependence on particular prey species. Using aphids as model organism, we tested the hypothesis that herbivore abundance increases in fragmented habitats is a result of reduced predator and parasitoid densities. In a 3 year-study, we examined the population dynamics of aphids with respect to host plant abundance and ant nest density in experimentally fragmented calcareous grasslands at two sites in the northern Jura mountains. Fragments of different size (area: 20.25 m², 2.25 m² and 0.25 m²) were isolated by a 5 in wide strip of frequently mown vegetation and corresponding control plots were situated in the adjacent undisturbed grassland. Aphid density was higher in fragments than in control plots. This was a combined result of a higher frequency of aphid-infested plants and larger aphid colonies in fragments than in control plots. Furthermore, a larger proportion of aphid colonies was ant-attended in fragments than in control plots. Aphid colonies were also more frequently visited by ants in fragments than in control plots in one of the 3 years. Parasitoid pressure on aphids was not influenced by the experimental fragmentation. Neither were aphid species richness and diversity affected by the fragmentation. Our study shows that even small-scale habitat fragmentation can have profound effects on the abundance of herbivorous insects. The effect on aphid density was consistent over 3 years and two sites with slightly different aphid communities.

Keywords: habitat fragmentation - extrafloral nectaries - goldenrod aphids - plant-quality - species loss - ants - association - competition - subdivision - mutualists

2003  Forest perception and knowledge of hikers and mountain bikers in two different areas in Northwestern Switzerland — Heer C, Rusterholz H-P & Baur B — Environmental Management 31: 709–723   doi> 10.1007/s00267-003-3002-x 

Recreational activities can have major impacts on vegetation and wildlife in frequently visited forests. We assessed forest perception and knowledge (state, functions, and species diversity) among hikers and mountain bikers in a frequently visited, seminatural suburban recreation forest (Muttenz) and in a more distantly situated, naturally grown excursion forest (Wasserfallen) in northwestern Switzerland. In all, 239 hikers and 126 mountain bikers were interviewed. Mountain bikers in both forests and hikers in the more intensely used recreation forest at Muttenz assessed the state of the forest less optimistically and showed a higher awareness of the negative impact of recreational activities on the flora and fauna than hikers at Wasserfallen. Furthermore, mountain bikers seemed aware of the social conflicts caused by their activity, since they appreciated neutral or positive encounters with other forest visitors. In contrast, 57% of hikers at Muttenz reported on negative experiences with other forest visitors, particularly with mountain bikers. In general, the interviewees' ecological and biological forest knowledge (forest type and function, species diversity) was rather high. A large proportion was aware of the pros and cons of different forest conditions for plants and animals, and could name or recognize at least some plant and/or animal species typical for the visited forest. The forest knowledge was neither influenced by the type of recreational activity carried out nor by any aspect of forest visit behavior (frequency and duration of forest visits, means of transportation and travel distance to forest). However, the interviewees' forest knowledge was influenced by their age and educational level.

Keywords: forest recreation - forest visitor groups - forest conditions - recreation impact - social conflicts - visitor survey

2003  Mitochondrial differentiation in a polymorphic land snail: evidence for Pleistocene survival within the boundaries of permafrost — Haase M, Misof B, Wirth T, Baminger H & Baur B — Journal of Evolutionary Biology 16: 415–428   doi> 10.1046/j.1420-9101.2003.00542.x 

The genetic differentiation of populations having colonized formerly unsuitable habitats after the Pleistocene glaciations depends to a great extent on the speed of expansion. Slow dispersers maintain their refugial diversity whereas fast dispersal leads to a reduction of diversity in the newly colonized areas. During the Pleistocene, almost the entire current range of the land snail Arianta arbustorum has repeatedly been covered with ice or been subjected to permafrost. Owing to the low potential for dispersal of land snails, slow (re)colonization of the wide range from southern refugia can be excluded. Alternatively, fast, passive dispersal from southern refugia or survival in and expansion from multiple refugia within the area subjected to permafrost may account for the current distribution. To distinguish between these scenarios we reconstructed a phylogeography based on the sequences of a fragment of the cytochrome oxidase I from 133 individuals collected at 45 localities and analysed the molecular variance. Seventy-five haplotypes were found that diverged on average at 7.52% of positions. This high degree of diversity suggests that A. arbustorum is an old species in which the population structure, isolation and the hermaphroditic nature have reduced the probability of lineage extinction. The genetic structure was highly significant with the highest variance partition found among regions. Geographic distance and mitochondrial differentiation were not congruent. Lineages had overlapping ranges. The clear genetic differentiation and the patchy pattern of haplotype distribution suggest that colonization of formerly unsuitable habitats was mainly achieved from multiple populations from within the permafrost area.

Keywords: AMOVA - Arianta arbustorum - dispersal - mitochondrial DNA - phylogeography - Pleistocene - polymorphism - refugia

2003  Polymorphic microsatellite loci in the endangered Indian rhinoceros, Rhinoceros unicornis — Zschokke S, Gautschi B & Baur B — Molecular Ecology Notes 3: 233–235   doi> 10.1046/j.1471-8286.2003.00400.x 

Eleven novel polymorphic microsatellite loci are presented for the highly endangered Indian (or greater one horned) rhinoceros Rhinoceros unicornis (Mammalia: Rhinocerotidae). These will be used to analyse the genetic variability within and between the two remaining large populations of the Indian rhinoceros and to manage captive breeding.

Keywords: captive breeding - microsatellite - population genetics - Rhinoceros unicornis

Genbank accession numbers: AJ508894 - AJ508904

2002  Small-scale habitat fragmentation effects on pollinator behaviour: experimental evidence from the bumblebee Bombus veteranus on calcareous grasslands — Goverde M, Schweizer K, Baur B & Erhardt A — Biological Conservation 104: 293–299   doi> 10.1016/S0006-3207(01)00194-X 

We examined visiting patterns of pollinators of Betonica officinalis L. (Lamiaceae) in experimentally fragmented calcareous grasslands and corresponding control plots at two study sites (Movelier and Nenzlingen) in the north-western Swiss Jura mountains. Fragments (1.5x1.5 m) were isolated by a 5-m wide strip of frequently mown vegetation while the control plots were situated in the adjacent undisturbed vegetation. The most common pollinator, the bumblebee Bombus veteranus (Apidae), visited fragments 53.7% less frequently than control plots. Furthermore, a change in foraging behaviour of Bombus veteranus was observed. In fragments the bumblebees visited more inflorescences, flew longer total visiting distances and the visiting time per patch tended to be higher than in control plots. The distribution of angles between arrival and departure direction (turning angles) differed from a uniform distribution in fragments but not in control plots. The increased directionality of bumblebee flight might be due to a decrease in floral rewards. Our results show that small-scale habitat fragmentation can affect plant pollination at two levels both relevant for plant fitness. First, lower visitation rates indicate a limitation of pollinators which might result in reduced seed set of the pollinated plant. Second, changes in pollinator behaviour might reduce pollen dispersal among flowers, increase inbreeding and hence reduce genetic variability in populations of this bumblebee pollinated plant.

Keywords: Betonica officinalis - Bombus veteranus - bumblebee - gene flow - plant-pollination interaction

2002  Changes in gastropod assemblages in freshwater habitats in the vicinity of Basel (Switzerland) over 87 years — Baur B & Ringeis B — Hydrobiologia 479: 1–10   doi> 10.1023/A:1021008010386 

The gastropod fauna in 18 freshwater habitats (streams, rivers and ponds) in the vicinity of Basel, first surveyed in 1906/1907, was re-examined in 1994. The freshwater snail fauna changed considerably over 87 years. One species (Aplexa hypnorum) recorded in 1906/1907 was not found in 1994, most probably it had become extinct in the period between the two surveys. Ten species were found in 1994, but not in 1906/1907. Two of them could not have been recorded in the first survey: the recently invading Potamopyrgus antipodarum and Ferrissia wautieri, a species first described in 1960. In contrast to these changes a part of the gastropod species appear to have a rather constant occurrence. All ten gastropod species found in both surveys showed similar percentage of occurrence (constancy) over 87 years. Species that were rare in 1906/1907 were also rare in 1994, and species common in the first survey were also common 87 years later. Interestingly, species considered as threatened throughout Switzerland towards the end of the 20th century (Red List species) were already rare at the beginning of the century in the habitats examined in the present study. The 1994 survey provides a baseline for monitoring future changes in snail species richness and abundance as riparian restoration actions are under-way or planned at several sites in the region of Basel.

Keywords: Gastropoda - species richness - species assemblage - conservation - Red List species - river Rhine

2002  Disturbance of forest by trampling: Effects on mycorrhizal roots of seedlings and mature trees of Fagus sylvatica — Waltert B, Wiemken V, Rusterholz H-P, Boller T & Baur B — Plant and Soil 243: 143–154   doi> 10.1023/A:1019983625473 

The effects of disturbance by recreational activities (trampling) on changes in soil organic matter (SOM) and on mycorrhizal roots of seedlings and mature trees were studied in four stands of a beech (Fagus sylvatica L.) forest near Basel, Switzerland. At each site, comparable disturbed and undisturbed plots were selected. Disturbance reduced ground cover vegetation and leaf litter. Beech seedlings had lower biomass after disturbance. Ergosterol concentration in seedling roots, an indicator of mycorrhizal fungi, was lower in two of the four disturbed plots compared to undisturbed plots; these two disturbed sites had especially low litter levels. Based on ergosterol measurements, mycorrhizas of mature trees did not appear to be negatively affected by trampling. Total fine roots and SOM were higher in the disturbed than in the undisturbed plots at three sites. At the fourth site, fine roots and SOM in the disturbed areas were lower than in the undisturbed areas most probably due to nutrient input following picnic activities. Principal component analysis revealed a close correlation between SOM and fine roots of mature trees as well as litter and seedling biomass. Trampling due to recreational activities caused considerable damage to the vegetation layer and in particular to the beech seedlings and their mycorrhizal fine roots, whereas, roots of mature trees were apparently resilient to trampling.

Keywords: ectomycorrhiza - ergosterol - Fagus sylvatica - fine roots - forest ecosystems - recreational activities - soil compaction - trampling - understorey

2002  Effects of experimental small-scale grassland fragmentation on the extent of grazing damage in Trifolium repens seedlings — Ledergerber S, Dolt C, Zschokke S & Baur B — Acta Oecologica 23: 329–336   doi> 10.1016/S1146-609X(02)01162-1 

We examined the extent of grazing damage to seedlings of white clover (Trifolium repens) in experimentally fragmented calcareous grasslands. The experimental set-up consisted of 12 blocks distributed over three sites. Each block contained one large (4.5x4.5 m), one medium (1.5x1.5 m) and two small (0.5x0.5 m) fragments and corresponding control plots (Zschokke et al 2000). Fragmentation was maintained by frequently mowing the area between the fragments. A fence around the study sites excluded large herbivores.
Seedlings of T. repens planted in petri dishes were exposed to invertebrate herbivores in fragments and control plots for 2-3 days both in summer and autumn. In summer - unlike autumn - grazing intensity expressed as leaf biomass loss per petri dish and day was 43% lower in fragments than in control plots. Grazing intensity in summer was positively correlated with relative gastropod density (number of individuals from 12 species), but not with relative grasshopper density (number of individuals from 15 species). In autumn, grazing intensity was correlated neither with gastropod nor with grasshopper density. It is suggested that a combination of factors can explain the seasonal difference in fragmentation effect on grazing intensity. Different herbivore species are active at different seasons and/or under different environmental conditions. Furthermore, different herbivore species react differently to the type of grassland fragmentation chosen in the present study. We conclude that fragmentation effects on grazing depend on which of the potential herbivore species react to fragmentation and which of them are active during the investigation period.

Keywords: habitat fragmentation - herbivory - gastropods - grasshoppers - calcareous grassland

2002  Habitat characteristics of the endangered flightless beetle Dorcadion fuliginator (Coleoptera: Cerambycidae): implications for conservation — Baur B, Zschokke S, Coray A, Schläpfer M & Erhardt A — Biological Conservation 105: 133–142   doi> 10.1016/S0006-3207(01)00117-3 

Habitat destruction and degradation are the major causes for the decline of the endangered grass-feeding flightless beetle Dorcadion fuliginator in Central Europe. We examined habitat characteristics at 19 localities which still support abundant D. fuliginator populations in the southern part of the Upper Rhine valley (border region of Switzerland, Germany and France) to obtain basic information for the management of deteriorating habitats with declining beetle populations. Populations of D. fuliginator were found in different types of grassland on south, south-west and south-east facing slopes and flat ground. Correspondence analysis showed that plant communities of D. fuliginator localities overlap widely with fertilized, dry hay meadows (phyto-sociologically defined as dry type of the Arrhenatheretum community) and to a minor extent with traditionally extensively cultivated dry grasslands (Xerobrometum and Teucrio-Mesobrometum communities). Average indicator scores of the plant communities characterize the habitat of D. fuliginator as fairly light-exposed and warm, but with relatively large ranges in humidity and nutrient content. The results of a 16-year study on the timing of emergence of the first beetles in a population provided further evidence for the high temperature requirements of D. fuliginator. Proposed conservation measures include traditional cultivation of the present secondary, man-made D. fuliginator habitats, introduction of beetles to suitable motorway embankments as well as large-scale measures allowing natural dynamics in the flood plain along the river Rhine, the presumably primordial habitat of this highly endangered beetle.

Keywords: beetle - grassland type - habitat degradation - habitat requirement - management plan - species conservation

2002  Inbreeding, outbreeding, infant growth, and size dimorphism in captive Indian rhinoceros (Rhinoceros unicornis) — Zschokke S & Baur B — Canadian Journal of Zoology 80: 2014–2023   doi> 10.1139/Z02-183 
Artikel als pdf Datei herunterladen
(© 2002 NRC Research Press Canada)

Effects of inbreeding and outbreeding on gestation period, birth weight, infant mortality, and growth, as well as the ontogeny of sexual size dimorphism were analyzed in captive Indian rhinoceroses using studbook data. Neither gestation period nor birth weight were affected by inbreeding. However, inbred calves grew slower and had a lower mortality rate than non inbred ones. It is suggested that the severe bottleneck experienced in the early 20th century by the Kaziranga population - from which most captive born Indian rhinoceroses descend - resulted in strong inbreeding with consequent purging of recessive lethal alleles. Outbred individuals (offspring of matings between individuals from the Kaziranga and the Chitwan populations) had a higher infant mortality rate, suggesting that the two populations are genetically partially incompatible.
Among captive individuals, adult males were found to be heavier (2300 kg) and larger (shoulder height = 172 cm) than females (1800 kg; 160 cm). There were, however, no sex differences in gestation period, birth weight or infant growth. This suggests that sexual dimorphism in adults is the result of a longer growth period in males rather than a difference in growth rate between the sexes.

Keywords: captive breeding - conservation biology - juvenile growth - life history - outbreeding depression - population bottleneck

2002  Intermating interval and number of sperm delivered in the simultaneously hermaphroditic land snail Arianta arbustorum (Pulmonata: Helicidae) — Hänggi C, Locher R & Baur B — The Veliger 45: 224–230

The number of sperm delivered is an important determinant for achieving fertilization in sperm competition. Hermaphroditic gastropods with short mating intervals may deplete their autosperm reserves, An earlier study showed that individuals of the simultaneously hermaphroditic land snail Arianta arbustorum need at least 8 days to replenish their autosperm reserves after a successful copulation. and that the number of sperm transferred in the second copulation slightly increased up to an intermating interval of 4 weeks. We compared spermatophore size. number of sperm delivered, and mating behavior in snails with longer intermating intervals. Snails that remated after 7-8 weeks did not differ in spermatophore size and number of sperm transferred from individuals that remated after 3-4 weeks. The number of sperm delivered averaged 2,151,000 in the first copulation and 2.130.000 in the second Copulation. Snails with a longer intermating interval showed a shorter courtship. but did not differ in copulation duration from snails which remated after 3-4 weeks. Furthermore, different intermating intervals did not affect female fecundity (number of eggs produced and hatching success of eggs). These results indicate that A. arbustorum entirely replenishes its autosperm reserves within 3-4 weeks after a successful copulation.

Keywords: Gastropoda - populations - spermatozoa - size - stylommatophora - Opisthobranchia - allocation - storage

2002  Nutritional stress changes sex-specific reproductive allocation in the simultaneously hermaphroditic land snail Arianta arbustorum — Locher R & Baur B — Functional Ecology 16: 623–632   doi> 10.1046/j.1365-2435.2002.00657.x 

1 Sex allocation theory predicts that when resources are limited in simultaneous hermaphrodites, the allocation to one sexual function will automatically reduce the resources available to the other function. This study examines the effect of nutritional stress on mating behaviour and male and female reproductive output (dry mass and nitrogen contents of spermatophores, sperm delivered and eggs deposited) in individuals of the simultaneously hermaphroditic land snail Arianta arbustorum kept under three different food regimes: ample (100%), restricted (50%) and extremely restricted (25%) food supply.
2 Independent of the extent of nutritional stress, 10–12% of the resources taken up were invested in reproductive output (both gender functions together) and 88–90% in maintenance (including faeces and excretion).
3 Courtship and copulation behaviour was affected by nutritional stress. Snails with an extremely restricted food supply did not mate, except one pair. Individuals with restricted food supply tended to court longer, and copulated for a shorter period, than individuals with ample food supply.
4 Nutritional stress did not affect the number of sperm delivered. However, snails with a restricted food supply produced fewer eggs. Thus, snails kept under nutritional stress invested relatively more resources in the male function than in the female function. Nevertheless, the absolute reproductive output remained highly female biased (>95% in all experimental groups).
5 At the individual level, the existence of a trade-off between resources invested in the male vs the female function could not be confirmed. However, there was a trade-off between nitrogen allocated to reproductive function and maintenance in snails with a restricted food supply.

Keywords: hermaphrodite - reproductive output - sex allocation - sperm competition

2001  Effects of habitat fragmentation on choke disease (Epichloë bromicola) in the grass Bromus erectus — Groppe K, Steinger T, Schmid B, Baur B & Boller T — Journal of Ecology 89: 247–255   doi> 10.1046/j.1365-2745.2001.00538.x 

1. The fungal endophyte Epichloe bromicola causes choke disease on Bromus erectus, thereby suppressing maturation of host inflorescences. We conducted a 3-year field experiment to investigate the effects of small-scale habitat fragmentation on the occurrence of choke disease in three calcareous grasslands in the Swiss Jura Mountains, where, overall, 4.3% of all flowering tillers had diseased inflorescences.
2. The number of diseased B. erectus plants (presumed genets), the number of tillers with diseased inflorescences, and the number of tillers with healthy inflorescences were counted over 3 years, but healthy tillers could not be allocated to particular genets. Each of 12 blocks contained one large (4.5 x 4.5 m), one medium (1.5 x 1.5 m) and two small (0.5 x 0.5 m) fragments and corresponding control plots. The percentage of tillers in the plots that were infected but did not show disease symptoms (asymptomatic plants) was estimated in the final year of the study using a diagnostic polymerase chain reaction. On average 1.7% of all tillers without disease symptoms were infected.
3. There were significantly more diseased plants in fragment than in control plots, particularly in small fragment plots or in the third year of the study, indicating that disease incidence in the host plant increased after fragmentation if assessed at the level of the genet population. This was probably due both to a switch of genets from the asymptomatic to the symptomatic state and to increased horizontal transmission of the disease in fragments.
4. The increase in the number of flowering tillers with diseased inflorescences was outweighed by that in the number of tillers with healthy inflorescences. Disease incidence was therefore decreased by fragmentation if assessed at the level of the host flowering tiller population. The effect on healthy plants was probably due to beneficial abiotic edge effects following fragmentation.
5. Plot size affected fragmentation response, with the largest increases in small, followed by medium and large fragments. Similarly, the strength of fragmentation responses increased through time over the 3-year study period.
6. Significant site to site and year to year variation in the number of diseased plants and in the number of tillers with diseased inflorescences suggested that separate experiments with replication within site and year would have yielded a series of interesting but individually different results. Only by repeating the experiments at several sites and over several years was it possible to obtain the general results reported in the previous points.

Keywords: calcareous grassland - clonal plants - diagnostic polymerase chain reaction (PCR) - endophytes - environmental change - habitat fragment size -plant-pathogen interactions

2001  Isolation of microsatellite markers in the hermaphroditic land snail Arianta arbustorum (Gastropoda) — Locher R & Baur B — Molecular Ecology Notes 1: 39–40   doi> 10.1046/j.1471-8278.2000.00016.x 

Five novel polymorphic microsatellite loci are presented for the simultaneously hermaphroditic land snail Arianta arbustorum. The isolation protocol was adapted from Estoup & Turgeon. Because wild multiple mating with different partners has been observed in this gastropod, the microsatellite loci presented will be an efficient tool for paternity analysis.

Keywords: Arianta arbustorum - microsatellites - snail - sperm competition

2001  Viability of lichen photobionts after passing through the digestive tract of a land snail — Fröberg L, Berg CO, Baur A & Baur B — Lichenologist 33: 543–545   doi> 10.1006/lich.2001.0355 

2000  Short-term responses of plants and invertebrates to experimental small-scale grassland fragmentation — Zschokke S, Dolt C, Rusterholz H-P, Oggier P, Braschler B, Thommen GH, Lüdin E, Erhardt A & Baur B — Oecologia 125: 559–572   doi> 10.1007/s004420000483 
Artikel als pdf Datei herunterladen
(© Springer Verlag)
The original publication is also available on LINK

The fragmentation of natural habitats is generally considered as a major threat to biodiversity. We investigated short-term responses of vascular plants (grasses and forbs) and four groups of invertebrates (ants, butterflies, grasshoppers and gastropods) to experimental fragmentation of calcareous grassland in the north-western Jura mountains, Switzerland. Three years after the initiation of the fragmentation -- which was created and maintained by mowing the area between the fragments -- we compared species richness, diversity and composition of the different groups and the abundance of single species in fragments of different size (area: 20.25 m², 2.25 m² and 0.25 m²) with those in corresponding control plots. The abundances of 19 (29%) of the 65 common species examined were affected by the fragmentation. However, the experimental fragmentation affected different taxonomic groups and single species to a different extent. Butterflies, the most mobile animals among the invertebrates studied, reacted most sensitively: species richness and foraging abundances of single butterfly species were lower in fragments than in control plots. Of the few other taxonomic groups or single species that were affected by the experimental fragmentation, most had a higher species richness or abundance in fragments than in control plots. This is probably so because the type of fragmentation used is beneficial to some plants through a decreased competition intensity along the edge of the fragments, and because some animals may use the fragments as retreats between their foraging bouts into the mown isolation area.

Keywords: biodiversity - calcareous grassland - habitat fragmentation - species richness - retreat effect

2000  Consumption rates and food preferences of slugs in a calcareous grassland under current and future CO₂ conditions — Peters HA, Baur B, Bazzaz F & Körner C — Oecologia 125: 72–81   doi> 10.1007/PL00008893 

This study explored consumption of a generalist herbivore feeding on leaf tissue of various plant species of a calcareous grassland, and tested whether consumption levels and preferences changed when plants were exposed to 5 years of in situ CO₂ enrichment. The first part of this experiment tested whether the consumption patterns of slugs (Deraceras reticulatum) observed in single-species feeding tests were altered when slugs were given a choice of food sources. Overall consumption increased 270% when slugs were given a choice, and they preferred having a choice of food sources more than they preferred having any one food source. Surprisingly, slugs consumed fewer legumes and grasses and more non-leguminous forbs when given a choice. In the second part of this experiment, feeding behaviors of slugs in response to elevated CO₂ were investigated by feeding them leaves of two legumes, one grass, and a non-leguminous forb (Trifolium medium, Lotus corniculatus, Bromas erectus, and Sanguisorba minor, respectively) in two or four species combinations. In the leguminous species mix, the non-leguminous species mix, and the combined mix (legumes and non-legumes), neither overall consumption by herbivores nor species preference was significantly altered by long-term CO₂ enrichment. In the combined species mix, slugs preferred legumes to non-legumes (P=0.012) and exhibited a weak functional group preference shift from non-legumes to legumes (P=0.089) in response to CO₂ enrichment. This is the first time such a shift has been observed, and provides evidence that there may be multiple herbivore responses to rising atmospheric CO₂ concentrations. Numerous single-species feeding tests using insects have shown that consumption by herbivores may increase when herbivores are fed plants grown in enriched CO₂ atmospheres. This study clearly demonstrates the limited applicability of non-choice feeding trials to generalist herbivores in species-rich communities.

2000  Ecological observations on Arianta aethiops aethiops (Helicidae), a land snail endemic to the South Carpathian mountains — Baur B, Schileyko AA & Baur A — Journal of Molluscan Studies 66: 285–289   doi> 10.1093/mollus/66.2.285 

Keywords: conservation - arbustorum

2000  Freizeitnutzung des Allschwiler Waldes: Einfluss auf Bodenvegetation, Strauchschicht und bodenlebende wirbellose Kleintiere — Rusterholz H-P, Stingelin K & Baur B — Schweizerische Zeitschrift für Forstwesen 151: 117–126   doi> 10.1658/1402-2001(2005)008[0175:DOSFFB]2.0.CO;2 

Keywords: deciduous forest - human trampling - picnic site - restoration - soil compaction - species composition

2000  Genetic variability in subpopulations of the asp viper Vipera aspis in the Swiss Jura mountains: implications for a conservation strategy — Jäggi C, Wirth T & Baur B — Biological Conservation 94: 69–77   doi> 10.1016/S0006-3207(99)00162-7 

We examined the genetic variability and structure in 20 subpopulations belonging to seven populations of the threatened snake Vipera aspis in the Swiss Jura mountains (n = 114) and in two subpopulations from central France (n = 12) using RAPDs (seven primers produced 70 polymorphic bands). The analysis of molecular variance (AMOVA) showed that the within-populations genetic variability accounted for 87.0% and the among-populations variability for 13.0% of the total variability. The within-subpopulation genetic variability accounted for 74.3%, the among-subpopulation variability within populations for 21.5% and the among-population variability for 4.2% of the total variability. An unweighted pair group method with arithmetic means (UPGMA)-cluster analysis based on mean Jaccard distances did not assemble the subpopulations according to their populations. The combined results of the AMOVA and the cluster analysis suggest that gene flow may have occurred over large parts of the snake's distribution area. In large subpopulations the genetic variability was larger than in small subpopulations. There was no difference in the genetic variability between connected and isolated subpopulations. We suggest that habitat management may prove to be more effective in maintaining the genetic variability of V. aspis in the north-western Swiss Jura mountains than any translocation of individuals.

Keywords: Vipera aspis - genetic variability - conservation strategy - random amplified polymorphic DNA (RAPD)

2000  Incidence of dart shooting, sperm delivery, and sperm storage in natural populations of the simultaneously hermaphroditic land snail Arianta arbustorum — Baminger H, Locher R & Baur B — Canadian Journal of Zoology 78: 1767–1774   doi> 10.1139/cjz-78-10-1767 

In several families of terrestrial pulmonates, simultaneously hermaphroditic animals form a sharp, hard, calcified or chitinous structure (the so-called love dart) in the female part of their reproductive organs. The dart is used to pierce the body of the mating partner during courtship. The adaptive significance of this peculiar behaviour is still little understood. We examined dart shooting, autosperm delivery, and allosperm storage in three natural populations of the simultaneously hermaphroditic land snail Arianta arbustorum in the Austrian Alps. Twenty-six (30.2%) of 86 copulating snails used their dart. The frequency of dart shooting tended to vary among populations. There was no reciprocity in dart shooting: individuals shot their dart independently of the behaviour of the mating partner. The number of spermatozoa delivered ranged from 522 000 to 4 238 000 (mean 1 706 000). The occurrence of dart shooting was related to neither the number of sperm delivered nor the number received from the partner. The occurrence of dart shooting was not influenced by the amount of allosperm from previous matings stored in the spermatheca of the dart shooters in two populations. In the third population, however, dart shooters had stored more allosperm in their spermatheca than non-shooters. The number of sperm received was not correlated with the size of the donor or the size of the recipient, indicating that snails do not allocate more sperm to larger partners. Experimental results showed that snails which mated under laboratory conditions did not differ in dart-shooting frequency from snails which mated in the wild.

Keywords: Helix aspersa - love-dart - spermathecal morphology - Gastropoda - courtship - Pulmonata - spermatozoa - Helicidae - Mollusca - calcium

2000  Intra- and inter-litter variation in life-history traits in a population of fire salamanders (Salamandra salamandra terrestris) — Kopp M & Baur B — Journal of Zoology 250: 231–236   doi> 10.1017/S0952836900002089 

We examined intra- and inter-litter variation in larval life-history traits in relation to maternal weight and date of larval deposition in a population of fire salamanders Salamandra salamandra terrestris in northwestern Switzerland. We also examined whether the timing of larval deposition by female fire salamanders is an adaptive strategy to the changing conditions of a temporary brook. Litters differed in mean weight at birth, weight at metamorphosis, and duration of the larval period. Mean weight at birth tended to be larger in litters deposited later in the season than in those deposited earlier. Large neonates reached metamorphosis more rapidly than small ones. A short larval period resulted in a small size at metamorphosis, indicating a fitness trade-off between duration of the larval period and size at metamorphosis. Within litters, successively-born larvae tend to decrease in body size, especially in litters with a relatively large variation in weight at birth. The results suggest that environmental factors such as floods or drying out of the brook may influence the timing of larval deposition.

Keywords: Salamandra - life-history - larval period - size at birth - size at metamorphosis

2000  Mating frequency and resource allocation to male and female function in the simultaneous hermaphrodite land snail Arianta arbustorum — Locher R & Baur B — Journal of Evolutionary Biology 13: 607–614   doi> 10.1046/j.1420-9101.2000.00206.x 

It is generally assumed that butterflies, as is the case with many holometabolous insects, rely primarily on nutrients gathered by larval feeding for somatic maintenance and fecundity. These reserves can be supplemented by adult feeding and in some cases by nuptial gifts passed from the males to the females during mating. Recent findings indicate that female butterflies detect and prefer nectar with high levels of amino acids, thus calling new attention to this nutritive source. Polyandrous species can further supplement their larval stores with additional nuptial gifts. This study examined how mating frequency of the polyandrous butterfly Pieris napi affects the female's preference for nectar amino acids. Females of this species generally detect and prefer nectar mimics containing amino acids. However, nectar amino acid preference is significantly lower in mated females. Furthermore, nectar amino acid preference increases when females are not allowed to remate, whereas the preference of twice-mated females remains constant at a lower level. These results indicate a versatile response of females to nectar amino acids, depending on their nutritional status; they may even switch their source of amino acids between adult feeding and nuptial gifts.

2000  Social facilitation affects longevity and lifetime reproductive success in a self-fertilizing land snail — Baur B & Baur A — Oikos 88: 612–620   doi> 10.1034/j.1600-0706.2000.880318.x 
Artikel als pdf Datei herunterladen

Factors that reduce the reproductive output of self-fertilizing hermaphrodites are receiving increasing attention. The combined effects of reduced Fecundity of selfing parents and inbreeding depression of the progeny have been referred to as self-fertilization depression. In isolated freshwater snails the reproductive output of selfing individuals also decreases due to the lack of social facilitation (absence of a conspecific). We examined the effect of social facilitation on lifetime reproductive success (number of young produced and longevity) over two generations in the simultaneously hermaphroditic land snail Balea perversa. In a parallel study we showed that B. perversa kept singly and in pairs reproduced exclusively by self-fertilization. In the parent generation, snails kept singly produced less offspring than snails kept in pairs. The difference in lifetime number of young was mainly due to differences in adult life span. Snails of the two groups did not differ in reproductive rate (number of young produced per 100 d of reproductive life) and hatchling size. In the offspring generation, snails kept singly did not differ from individuals kept in pairs in the lifetime number of young and hatchling survival. As in the parent generation, snails kept singly reproduced during a shorter period than snails kept in pairs. However. the shorter reproductive life span of snails kept singly was compensated for by a slightly (but not significantly) higher reproductive rate which resulted in a similar number of offspring produced for both groups. In both generations, snails of the two groups did not differ in size at first reproduction, adult growth rate and size at death. These findings suggest that social facilitation may affect longevity in selfing B. perversa.

Keywords: fresh-water snail - Balea perversa - Arianta arbustorum - mating system - inbreeding depression - calcicolous lichens - growth - rates - competition - gastropods

2000  Sperm delivery and egg production of the simultaneously hermaphroditic land snail Arianta arbustorum exposed to an increased sperm competition risk — Locher R & Baur B — Invertebrate Reproduction and Development 38: 53–60   doi> 10.1080/07924259.2000.9652436 

Sperm competition theory predicts that males exposed to an increased risk of sperm competition should maximize fertilization prospects by inseminating more sperm per ejaculate. We designed a laboratory experiment to examine the effect of increased sperm competition risk on male and female reproductive traits in individuals of the simultaneously hermaphroditic land snail Arianta arbustorum. Courtship behaviour, spermatophore size and number of sperm delivered were not influenced by a higher sperm competition risk. However, snails constantly exposed to mucous trails of conspecifics deposited more egg batches than snails denied any cues from conspecific mucous trails. On the individual level, the number of sperm delivered was positively correlated with the number of eggs produced. This finding contradicts the basic prediction of sex allocation theory that there is a trade-off between resources allocated to male and female function in simultaneous hermaphrodites. Most probably this trade-off may only occur if resources are limited.

Keywords: Arianta arbustorum - land snail - reproduction - simultaneous hermaphrodite - sperm competition risk

2000  Ultrastructure of snail grazing damage to calcicolous lichens — Baur B, Fröberg L, Baur A, Guggenheim R & Haase M — Nordic Journal of Botany 20: 119–128

The identification of damaged lichens is often difficult due to changes in the morphology of regenerating specimens. We examined the ultrastructure of grazing damages to four species of calcicolous lichens (Aspicilia calcarea, Physcia adscendens, Tephromela atra and Xanthoria parietina) and free-living cyanobacteria (family Chroococcaceae) caused by individuals of four species of land snails (Chondrina clienta, Balea perversa, Clausilia bidentata and Helicigona lapicida). We also investigated the radular structure of the four lichen-feeding snails to examine whether differences in radular morphology result in species-specific grazing damages. Individuals of all four snail species removed the cyanobacteria layer covering the limestone or lichen surfaces. The four lichen species were grazed to a different extent by the different snail species. SEM-images showed that B. perversa left distinct depressions on the thalli of A. calcarea, whereas H. lapicida grazed off the thalli of this lichen rather evenly. Both snail species left visible radular traces on the lichen surface. In contrast, Ch. clients left shallow depressions without radular traces on the thalli of A. calcarea. In Tephromela atra, grazing damages were observed on both thallus and ascocarp. Ascocarps of T. atra were partly grazed by B. perversa. Helicigona lapicida grazing on T. atra removed more or less evenly the entire lichen tissue including the ascocarps. In foliose lichens, grazing by Ch. clienta, B. perversa and CI. bidentata resulted in depressions of different depths, while H. lapicida removed entire pieces of the thalli. In general, radular traces were less distinct in foliose lichens than in crustose lichens.

Keywords: dwelling land snails - Chondrina clienta - Balea perversa - oribatid mites - herbivory

1999  Effects of intermating interval on spermatophore size and sperm number in the simultaneously hermaphroditic land snail Arianta arbustorum — Locher R & Baur B — Ethology 105: 839–849   doi> 10.1046/j.1439-0310.1999.00452.x 

We examined the effect of intermating interval on spermatophore size and number of sperm delivered in the simultaneously hermaphroditic land snail, Arianta arbustorum. Snails that remated after 6-7 d transferred smaller spermatophores which contained fewer sperm than snails that remated after eight and more days. This indicates that individuals of A. arbustorum need at least 8d to completely replenish their sperm reserves after a successful copulation. We suggest that the interval between two copulations is also influenced by the energy costs of the longlasting courtship behaviour with extensive mucus production.

Keywords: competition games - gastropoda - allocation - depletion - pulmonata - cricket - choice

1999  Overgrowing forest as a possible cause for the local extinction of Vipera aspis in the northern Swiss Jura mountains — Jäggi C & Baur B — Amphibia-Reptilia 20: 25–34   doi> 10.1163/156853899506870 

In the northern Swiss Jura mountains, the Asp viper Vipera aspis was common until the 1940ies. During the past 50 years many local populations went extinct and nowadays the species is considered as threatened. We compared habitat characteristics of localities with extant viper populations with those of localities where the species became extinct. These two groups of localities did not differ in exposure, altitude, inclination, soil structure and cover of ground vegetation. However, localities where the species is still found were situated more frequently at forest edges, in dry meadows and at roadsides, whereas localities in which V. aspis became extinct were situated more frequently in forests. Tree density was lower at localities where the viper is still present. The results suggest that former habitats of V. aspis became overgrown by bushes and trees, which in turn may have led to a colder, more humid and thus unfavourable microclimate for V. aspis. We conclude that logging is an essential tool to maintain suitable habitat for this thermophilous ovoviviparous reptile.

Keywords: sympatric snake populations - habitat - ecology

1998  Sperm competition in molluscs — Baur B — In: Sperm Competition and Sexual Selection (Birkhead TR & Møller AP, Red). Academic Press, London: 255–305

Molluscs are numerically the second largest phylum in the animal kingdom with more than 120'000 living species, which are divided into eight classes. The visual differences between a snail, a clam, and a squid, each an example of a major class of the molluscs, belie the closeness of their relationship. Sexual behaviour is also extremely variable in this phylum. Many species are promiscuous and there are different forms of sperm storage, providing the potential for sperm competition. However, with few exceptions, evolutionary and behavioural aspects of sperm competition have not been examined in this phylum. Most of the available evidence for sperm competition is molluscs is published in studies with other aims and therefore is indirect.
This chapter presents different lines of evidence which suggest that sperm competition might be important in the evolution of the reproductive behaviour in some groups of molluscs. It also shows that there are huge gaps in our understanding of the reproductive behaviour of molluscs. [...] The following provides a taxonomic account of reproductive morphology, physiology and behaviour that potentially have implications for sperm competition.

1998  Sperm allocation in the simultaneously hermaphroditic land snail Arianta arbustorum — Baur B, Locher R & Baur A — Animal Behaviour 56: 839–845   doi> 10.1006/anbe.1998.0855 
Artikel als pdf Datei herunterladen

To test the idea that individuals of the simultaneously hermaphroditic land snail Arianta arbustorum can control the number of spermatozoa in their spermatophores, we investigated whether they differentially release sperm to virgin or nonvirgin partners with respect to the potential risk of sperm competition in a given mating. The number of sperm transferred ranged from 802 620 to 3 968 800 (x̄ = 2 185 100; N=91), but was related neither to the mating history of the partner nor to copulation duration. This indicates that individuals of A. arbustorum are not able to adjust sperm expenditure to the mating history of the partner. Furthermore, the number of sperm transferred was correlated neither with the size of the donor nor with the size of the recipient. It has been proposed that the sexual conflict between the two genders in simultaneous hermaphrodites could be resolved by gamete trading. Theory predicts that sperm trading should occur in hermaphrodites in which the female role controls fertilization, for example in gastropods with a gametolytic gland and/or sperm. storage such as A. arbustorum. To see whether sperm trading occurs, we also examined whether individuals of A. arbustorum adjust the number of sperm they release to the number they receive from their mating partner. There was a high degree of reciprocity in spermatophore transfer: in 45 of the 46 mating pairs investigated both partners delivered a spermatophore that contained spermatozoa. The numbers of sperm transferred by the two mating partners were not correlated, however. This indicates that sperm trading does not occur in this simultaneously hermaphroditic land snail.

Keywords: alpine populations - competition games - polychaete worm - ejaculate size - female choice - clutch size - Gastropoda - Helicidae - Pulmonata - courtship

1998  A comparison of three methods for assessing the gastropod community in dry grasslands — Oggier P, Zschokke S & Baur B — Pedobiologia 42: 348–357

Three different methods (mark-release-recapture, cardboard trapping and soil sampling) were used to examine the community structure of terrestrial gastropods in an unfertilised, calcareous grassland in the Swiss Jura mountains. The three methods differ in the extent of disturbance to gastropods and damage to the vegetation, in weather dependence and in the spatial scale they can be applied. Although the species patterns obtained by these methods were similar, the three methods yielded different abundances in different species. This can partly be explained by the fact that gastropod species associated with dry grasslands are highly variable in their behaviour (activity rhythm, microhabitat preference and degree to which they climb on vegetation). However, Vertigo pygmaea was the most abundant snail species in all three methods used (82% of all individuals with mark-release-recapture, 58% with cardboard trapping and 58% with soil sampling). We conclude that cardboard trapping might be best suited to examine population biological questions in selected species over relatively large areas of grassland. In contrast, stratified soil sampling might be the most reliable method to obtain complete species lists (species richness) in small areas of grassland.

Keywords: population estimate - mark-release-recapture - cardboard trapping - soil sampling - gastropod community - species assemblage

1998  Altitudinal variation in size and composition of eggs in the land snail Arianta arbustorum — Baur A & Baur B — Canadian Journal of Zoology 76: 2067–2074   doi> 10.1139/z98-145 

Egg size and egg provisioning are crucial for the survival of offspring in invertebrates without postlaying egg care. The effects of elevation and size of the mother on egg size and on nitrogen and carbon concentrations in eggs were examined in eight populations of the land snail Arianta arbustorum over an altitudinal gradient from 370 to 2340 m in Switzerland. The dry mass of single eggs ranged from 1.48 to 2.79 mg and decreased with increasing altitude. Adult snail size (shell volume) also decreased with increasing elevation as did clutch size and reproductive investment (clutch size x egg dry mass) of mothers. Hatching success of eggs varied among populations, but showed no altitudinal pattern. When differences in parental shell size were taken into account, correlations between altitude and egg size, clutch size, and reproductive investment disappeared. Thus, the altitudinal decreases in egg size, clutch size, and reproductive investment were mainly due to smaller snail sizes at higher elevations. The nitrogen concentration in eggs ranged from 3.3 to 4.5% and decreased with increasing elevation. In contrast to egg and clutch size, the altitudinal variation in nitrogen concentration of eggs cannot be explained by differences in snail size. The carbon concentration in eggs ranged from 31.1 to 33.1%, but showed no altitudinal variation. Nitrogen and carbon concentrations in the eggshell and egg fluid in eggs from four populations were examined separately. The nitrogen concentration in the eggshell ranged from 0.7 to 1.8% and was lower than that of the egg fluid (5.1-5.8%). Similarly, the carbon concentration in the eggshell was lower (20.2-22.8%) than that in the egg fluid (35.8-40.2%). Interpopulation differences in egg composition may affect growth, size, and survival of hatchlings and the extent of egg cannibalism in A. arbustorum.

Keywords: alpine populations - nutrient content - life-history - clutch size - cannibalism - Pulmonata - Helicidae - density

1998  Feeding behaviour of juvenile snails (Helix pomatia) to four plants species grown at elevated atmospheric CO₂ — Ledergerber S, Leadley PW, Stöcklin J & Baur B — Acta Oecologica 19: 89–95   doi> 10.1016/S1146-609X(98)80012-X 

The feeding behaviour of juveniles of the land snail Helix pomatia was examined in model plant communities consisting of Trifolium repens, Hieracium pilosella, Bromus erectus and Prunella vulgaris that are common species in extensively managed calcareous grasslands in the Swiss Jura mountains. The plant communities were grown either at ambient (350 ppm) or elevated (600 ppm) CO₂ concentrations. Leaves of T. repens and P. vulgaris grown in elevated atmospheric CO₂ had a lower specific leaf area, and leaves of T. repens had lower percentage N on a dry weight basis than leaves grown under ambient CO₂ concentration. Snails fed on all four plant species, but showed a overwhelming preference for T. repens (percentages of total biomass consumed were 91.9 % at 350 ppm and 97.6 % at 600 ppm). The species-specific feeding intensity of juvenile H. pomatia did not differ between the two treatments. The total dry weight of T. repens consumed by the snails was marginally greater (P = 0.06) at elevated CO₂, but there were no significant differences in leaf N or leaf area eaten. These findings are similar to numerous other studies showing that invertebrates increase their consumption of plant material to balance reductions in plant N concentrations at elevated CO₂ treatments. Helix pomatia that fed on plants grown at elevated CO₂ atmosphere showed a larger increase in relative wet weight than those that fed on plants from ambient CO₂ conditions. However, the weight gain of H. pomatia was poorly correlated with amount of plant tissue consumed, so we suggest that the effect of CO₂ on weight gain in H. pomatia was due to a change in the quality of T. repens leaves.

Keywords: Helix pomatia - Trifolium repens - elevated carbon dioxide - herbivory - food choice

1998  Past and future breeding of the Indian rhinoceros in captivity — Zschokke S, Studer P & Baur B — International Zoo News 45: 261–276
Artikel als pdf Datei herunterladen

Link to full text (without illustrations)

We analyzed the demography and breeding history of captive greater one-horned, or Indian, rhinoceroses (Rhinoceros unicornis) and evaluated its genetic consequence on the zoo population using the studbook data up to 31 December 1996.
R. unicornis - one of the most endangered large mammals - is kept in captivity in zoological gardens and animal parks world-wide. Nowadays, 85 of the 129 individuals kept in captivity are zoo-born. Until recently however, little attention was paid to the genetic health of the zoo population.
In captivity, males and females reached a maximum age of 42 years, but only males reproduced beyond the age of 32 years. We found high juvenile mortality in both sexes (23% for males and 30% for females). Offspring of primiparous dams suffered higher juvenile mortality (40%) than those of multiparous dams (17%). In the data available, we could not find any inbreeding effects. The sex ratio of zoo-born R. unicornis was male-biased (60% males vs. 40% females). Despite the male-biased sex ratio, more females than males reproduced in captivity.
At present, 48.4% of the genes of all zoo-born R. unicornis stem from three founder individuals, whereas another 30 founders contributed to the remaining 51.6% of the genes. This unequal distribution leads to a low founder equivalent of 10.52. For a viable zoo population, a founder equivalent of at least 20 is considered to be necessary. Furthermore, 97% of all genes stem from founder individuals from a single, possibly highly inbred population in Assam (India).
We evaluated future breedings and show that as few as two offspring in a single zoo can influence the genetic health of the world-wide captive population. The difference in founder equivalents between the two hypothetical worst case breedings and the two best case breedings amounts to almost 10%.

Keywords: breeding management - captive breeding - inbreeding - mean kinship

1998  Threatened species in a vanishing habitat: plants and invertebrates in calcareous grasslands in the Swiss Jura mountains — Niemelä J & Baur B — Biodiversity and Conservation 7: 1407–1416   doi> 10.1023/A:1008835529764 

We examined the diversity of vascular plants, butterflies, grasshoppers, gastropods and carabid beetles in three calcareous grasslands in the northwestern Swiss Jura mountains, a habitat type that has decreased dramatically during the recent decades. As many as 58 species (ca 22%) of the 266 collected are listed as threatened in northern Switzerland. The number of threatened species ranged from 27 to 49 per site, and 26 species occurred in only one of the three grasslands. The species richness of butterflies and vascular plants correlated positively among the grasslands, while the species richness of other groups did not covary. An index of complementarity indicated that the species compositions (including non-threatened species, and spiders and oribatid mites) of the groups varied greatly among the grasslands. In addition, herbivorous groups were more widely distributed than predators among the three grasslands. Due to this variation in species composition none of the three sites can substitute for the others, if the biodiversity of these grasslands is to be maintained. Furthermore, the taxonomic groups studied are poor indicators of each others' diversity. Consequently, we support the 'shopping basket' approach to conservation evaluation, i.e. measuring species richness, species composition and complementarity of several groups instead of just one.

Keywords: species diversity - threatened species - indicator species - calcareous grassland - Switzerland

1997  Differences in resting-site preference in two coexisting land snails, Arianta arbustorum and Arianta chamaeleon (Helicidae), on alpine slopes — Ledergerber S, Baminger H, Bisenberger A, Kleewein D, Sattmann H & Baur B — Journal of Molluscan Studies 63: 1–8   doi> 10.1093/mollus/63.1.1 

Resting-site preference and patterns of spatial distribution were examined in the sympatric land snails Arianta arbustorum and A. chamaeleon on two opposite slopes in the south-eastern Alps, Austria. The two slopes did not differ in proportion of A. arbustorum and A. chamaeleon (74.4% vs. 25.6% on the NNE-exposed slope and 68.3% vs. 31.7% on the SSW-exposed slope). Individuals of both species showed aggregated dispersion patterns. The nearest-neighbour method indicated that in both species snail aggregations predominantly consisted either of A. arbustorum or A. chamaeleon on the NNE-exposed slope with a mosaic of rocks and distinct patches of different plants. On the SSW-exposed slope, which was less variable in vegetation cover, snail aggregations consisted of conspecific and hetero-specific individuals. Juvenile and adult A. arbustorum preferred to rest attached to leaves of Adenostyles alliariae, but avoided rock surfaces and patches of grass on the NNE-exposed slope. In contrast, juvenile and adult A. chamaeleon preferentially rested on rock surfaces, and also avoided grass patches. Juvenile and adult A. chamaeleon did not differ in resting-site preference, whereas small differences in resting sites were observed between juvenile and adult A. arbustorum. Differences in resting-site preference is one way of niche differentiation which may allow individuals of the two Arianta species to coexist.

Keywords: calcicolous lichens - food preferences - dispersal - patterns - density - morphs

1997  Grazing damage to plants and gastropod and grasshopper densities in a CO₂-enrichment experiment on calcareous grassland — Ledergerber S, Thommen GH & Baur B — Acta Oecologica 18: 255–261   doi> 10.1016/S1146-609X(97)80012-4 

Plant-herbivore interactions may change as atmospheric CO₂ concentrations continue to rise. We examined the effects of elevated atmospheric CO₂ and CO₂-exposure chambers on the grazing damage to plants, and on the abundances of potential herbivores (terrestrial gastropods and grasshoppers) in a calcareous grassland in the Jura mountains of Switzerland (village of Nenzlingen). Individuals of most plant species examined showed slight grazing damage. However, plots with CO₂ enrichment and plots with ambient atmosphere did not differ in the extent of grazing damage. Similarly, plots with CO₂ enrichment and plots with ambient atmosphere did not differ in either gastropod or grasshopper density. Experimental plots with and without chambers did not differ in the number of gastropods. However, the densities of gastropods and grasshoppers and extent of grazing damage to plants were generally lower in the experimental area than in the grassland outside the experimental field.

Keywords: herbivore - terrestrial gastropod - grasshopper - density - calcareous grassland - CO₂ enrichment - SACC-experiment

1997  Mating system and genetic variability in the simultaneously hermaphroditic terrestrial gastropod Balea perversa on the Baltic island of Öland, Sweden — Wirth T, Baur A & Baur B — Hereditas 126: 199–209   doi> 10.1111/j.1601-5223.1997.00199.x 

Random amplified polymorphic DNA (RAPD) technique was used to analyse the mating system of the simultaneously hermaphroditic land snail Balea perversa and to examine the level of generic variability in eight natural populations of this rock-dwelling gastropod on the Baltic island of Oland, Sweden. The mode of reproduction was assessed in parent-offspring comparisons, in which parents (virgin at the beginning of the breeding experiment or wild-caught individuals with prior reproductive experience) were kept either singly or in pairs. Snails with no prior reproductive experience produced 1-10 offspring exclusively by selfing, no matter whether they were kept singly or in pairs. In contrast, low rates of outcrossing occurred in snails with prior reproductive experience. Minimum estimates of outcrossing were 10% for snails kept singly and 16% for snails kept in pairs. Corresponding maximum likelihood estimates of outcrossing ranged From 16 to 25%. The results indicated that sperm stored from previous matings were used for cross-fertilization. At the population level, AMOVA analysis showed that most of the genetic variability (84%) occurred among populations of B. perversa and only 16% within populations. In two populations genetic variability was completely absent in the DNA fragment patterns examined. This finding agrees with the mode of reproduction in B. perversa. Frequent selfing may account for the low within-population variability compared with the moderate among-population variability in this species.

Keywords: fresh-water snails - inbreeding depression - self-fertilization - land snail - calcicolous lichens - natural-populations - outcrossing rates - evolution - plants - reproduction

1997  Random mating with respect to relatedness in the simultaneously hermaphroditic land snail Arianta arbustorum — Baur B & Baur A — Invertebrate Biology 116: 294–298   doi> 10.2307/3226861 

A previous study showed negative effects of inbreeding on reproductive success in the simultaneously hermaphroditic land snail Arianta arbustorum. Different mechanisms of inbreeding avoidance such as kin recognition, sex-biased dispersal patterns, and variation in mating systems have evolved in a variety of organisms. We performed mate-choice tests to examine whether individuals of A. arbustorum discriminate between full-sibs and non-sibs from the same population, and whether incestuous matings reduce the snails' subsequent reproductive success. Snails mated randomly with respect to degree of relatedness, indicating a lack of inbreeding avoidance by selective mating. Snails which mated with full-sibs did not differ in number of eggs, hatching success of eggs, and number of offspring produced from those mated with unrelated conspecifics. Our results indicate that there is no kin recognition mechanism in A. arbustorum. We suggest that multiple mating with different partners, as observed in the field, may reduce inbreeding effects in this species.

Keywords: inbreeding - mate choice - gastropod - pulmonate - hermaphrodite

1996  Variation in species richness of plants and diverse groups of invertebrates in three calcareous grasslands of the Swiss Jura mountains — Baur B, Joshi J, Schmid B, Hänggi A, Borcard D, Stary J, Pedroli-Christen A, Thommen GH, Luka H, Rusterholz H-P, Oggier P, Ledergerber S & Erhardt A — Revue Suisse de Zoologie 103: 801–833

Species richness and abundance of vascular plants and several groups of invertebrates (spiders, oribatid mites, diplopods, grasshoppers and bush crickets, ground beetles, butterflies and terrestrial gastropods) were recorded in three calcareous grasslands (Nenzlingen, Movelier and Vicques) in the northwestern Swiss Jura mountains. Species richness varied both between taxonomical groups and between sites (species richness ranges: 96-116 vascular plants, 60-66 spiders, 18 oribatid mites at each site, 1-7 diplopods, 10-16 grasshoppers and bush crickets, 19-21 ground beetles, 32-46 butterflies and 15-21 terrestrial gastropods). Species overlap (number of species that occurred at all sites) was relatively large in terrestrial gastropods (59.1%), butterflies (56.5%), vascular plants (53.8%) and grasshoppers (47.1%), but relatively low in oribatid mites (32.3%), spiders (25.0%), ground beetles (18.4%) and diplopods (12.5%). Diversity expressed by the Shannon-Wiener index (H') was compared for five groups of invertebrates. Diversity was largest in spiders and ground beetles and lowest in terrestrial gastropods. Different taxonomical groups had their maximum diversity at different sites: each grassland had the highest diversity in at least one group. The three sites also varied in the abundance of different invertebrate groups. Most groups had the highest densities in Nenzlingen and the lowest densities in Vicques. All three sites contained a high proportion of species listed in the Red Data Book of Switzerland with values averaging 49.5% in grasshoppers and bush crickets, 28.9% in butterflies, 18.9% in vascular plants, 11.2% in terrestrial gastropods, and 6.7% in ground beetles. One spider species (Oxyptila pullata) and two mite species (Epilohmannia cylindrica minima and Pergalumna myrmophila) were recorded for the first time in Switzerland.

1996  Chemical variation within and between individuals of the lichenized ascomycete Tephromela atra — Hesbacher S, Fröberg L, Baur A, Baur B & Proksch P — Biochemical Systematics and Ecology 24: 603–609   doi> 10.1016/S0305-1978(97)81204-5 

HPLC-analysis was used to determine the concentrations of the lichen compounds alectoronic acid (depsidon), alpha-collatolic acid (depsidon) and atranorin (depsid) in the lichenized ascomycete Tephromela atra (syn. Lecanora atra) (Hudson) Hafellner from limestone walls on the Baltic island of bland, Sweden. In 24 individuals of T. atra sampled on a stone wall, the pre-reproductive and reproductive tissue did not differ in the concentrations of alectoronic acid, collatolic acid and atranorin. The concentrations of the three lichen compounds were inter-correlated in the reproductive tissue, but not in the pre-reproductive tissue. Single individuals of T. atra ranged in area covered from 10.1 to 147.4 cm² (mean: 38.5 cm²; N=24); 38.6% of this area was pre-reproductive tissue. However, the concentrations of the three lichen compounds were correlated neither with the total area covered by the lichen nor with the percentage of pre-reproductive tissue. This suggests that the concentrations of the lichen compounds do not change with increasing size (age) of the lichen. Analysis of specimens of T. atra from eight localities revealed a significant variation in lichen compounds (range between localities: alectoronic acid 0.60-3.26 mu g/mg lichen dry weight (DW); collatolic acid 2.14-11.59 mu g/mg lichen DW; atranorin 0.58-4.16 mu g/mg lichen DW). The level of grazing observed in the lichens differed significantly among localities. However, no correlations between the concentrations of the three lichen compounds and the grazing damage to the lichens were found.

Keywords: lichens - lichen compounds - herbivory - defense - chemical variation

1996  Effects of population subdivision and catastrophes on the persistence of a land snail metapopulation — Akçakaya HR & Baur B — Oecologia 105: 475–483   doi> 10.1007/BF00330010 

We modeled the dynamics of a metapopulation of the land snail Arianta arbustorum in north-eastern Switzerland to investigate the effect of population subdivision on the persistence of a land snail metapopulation and to analyze the interaction between spatial factors, population subdivision, and catastrophes. We developed a spatially structured, stochastic, age-structured metapopulation model with field data from previous studies on the metapopulation in Switzerland and experimental and meteorological data. The model incorporated distance-dependent dispersal through stream banks, correlated environmental fluctuations, and catastrophes resulting from heavy rains. The results point to various complex interactions among factors involved in metapopulation dynamics and suggest that in some cases population subdivision may act to decrease threats from environmental fluctuations and catastrophes.

Keywords: Metapopulation model - simulation - extinction - spatial structure - catastrophes

1995  Habitat-related dispersal in the land snail Chondrina clienta — Baur B & Baur A — Ecography 18: 123–130   doi> 10.1111/j.1600-0587.1995.tb00332.x 

Habitat type may influence dispersal in a variety of animal species We examined dispersal in the rock-dwelling land snail Chondrina clienta m a limestone pavement, on vertical rock walls, a pile of stones and a stone wall on the Baltic island of Oland, Sweden. Dispersal was estimated by recording movements of marked C. clienta in natural populations over 3 yr Dispersal differed significantly between habitat types. The largest distances dispersed were recorded in the limestone pavement (264 cm yr, median distance) and on vertical rock walls (96 cm yr), simple habitats for travelling snails. Dispersal was less in the stone pile (68 cm yr) and on the stone wall (88 cm yr) that are more complex habitats with multiple layers of pieces of stones. Distances dispersed also varied among vertical rock walls, indicating that other factors such as exposure of the rock surface and size of the habitat may be important in determining snail dispersal. The results of two experiments indicated that grassland vegetation may inhibit dispersal in C.clienta, and that isolated stones covered with lichens might serve as stepping stones for dispersing snails in otherwise unsuitable grassland. Snail size (age) influenced distances moved, but might only be important in determining daily movements, not dispersal over longer periods. Dispersal in C. clienta is habitat-specific and cannot be characterized by a single parameter

1995  Sequestration of lichen compounds by three species of terrestrial snails — Hesbacher S, Baur B, Baur A & Proksch P — Journal of Chemical Ecology 21: 233–246   doi> 10.1007/BF02036654 

Three species of lichen-grazing snails,Balea perversa, Chondria clienta, and Helicigona lapicida, all from the Swedish island of Öland, were found to sequester lichen compounds when feeding on the crustous lichen species Aspicila calcarea, Caloplaca flavovirescens, Lecanora muralis, Physcia adscendens, Tephromela atra, and Xanthoria parietina. The lichen compounds detected in the soft bodies of the snail species analyzed included the anthraquinone parietin, the depside atranorin, as well as a presumable degradation product of the latter. Other lichen compounds such as (+)-usnic acid or agr-collatolic acid were not found in the soft bodies but were only detected in the feces, suggesting selective uptake of lichen compounds by the snails. In individuals of C. clienta initially fed on the lichen X. parietina, the amount of sequestered parietin decreased over time on a parietin-free diet but was still detectable in the soft bodies after 28 days. In the ovoviviparous land snail,B. perversa, sequestered parietin was transferred from the mother to the eggs in the reproductive tract.

Keywords: Balea perversa - Chondrina clienta - Helicigona lapicida - Gastropoda - Pulmonata - crustous lichens - lichen compounds -sequestration

1995  Species diversity and grazing damage in a calcicolous lichen community on top of stone walls in Öland, Sweden — Baur B, Fröberg L & Baur A — Annales Botanici Fennici 32: 312–323

Diversity of the calcicolous lichen flora and grazing damage to lichens were recorded on 12 limestone walls in the grassland Great Alvar on the Baltic island of Oland, southeastern Sweden. Grazing damage of lichens was compared with the abundance of potential lichen herbivores (land snails and oribatid mites). A total of 52 Lichen species, 2 lichen parasites, one alga, 2 bryophytes, one vascular plant (Sedum acre) and cyanobacteria, most of them belonging to the family Chroococcaceae, were found on the upper layer of the stone walls. The number of lichen species encountered on single stone walls ranged from 21 to 33. Between-wall differences in species richness were not due to differences in sampling effort. Similarity coefficients of species composition showed a high similarity of the lichen communities between stone walls. Aspicilia calcarea was the dominant lichen which covered on average 66.1% of the upper surface of the stone walls (range among stone walls: 11.9-89.8%). Grazing damage was recorded in 33 (63.5%) of the 52 lichen species. In general, lichen species that occurred frequently were more severely damaged than rare lichen species, although 5 frequent species showed no grazing damage at all. Six species of land snails and oribatid mites were encountered on the stone walls. Two of the snail species (Chondrina clienta and Balea perversa, both known as lichen feeders) were abundant on some stone walls. The proportion of lichen species that showed,orating damage was not influenced by the presence/absence (and density) of either snail species or mites except that the level of grazing damage in the dominant lichen species A. calcarea was correlated with the local population density of B. perversa.

Keywords: biodiversity - calcicolous lichens - gastropods - herbivory - mites - species diversity

1994  Dispersal in the land snail Chondrina avenacea on vertical rock walls — Baur B & Baur A — Malacological Review 27: 53–59

Keywords: dispersion - animal active movement - crowding - petrous bone - spatial variation - population density - forests - Switzerland - population dynamics - Europe - Gastropoda - Mollusca - Invertebrata

1994  Herbivory on calcicolous lichens: different food preferences and growth rates in two co-existing land snails — Baur A, Baur B & Fröberg L — Oecologia 98: 313–319   doi> 10.1007/BF00324219 

A total of 32 calcicolous lichen species, one alga and one bryophyte were recorded on a limestone wall in the grassland Great Alvar on the Baltic island of Öland, Sweden. Fourteen (41%) of these 34 species and free-living cyanobacteria showed herbivore damage, most probably due to grazing by the land snails Chondrina clienta and Balea perversa which inhabited the limestone wall. Three laboratory experiments were conducted to examine the food preferences of individuals of C. clienta and B. perversa collected at this site and to evaluate any association between their preference and the net food quality of the lichens to the snails. Chondrina clienta and B. perversa exhibited food preferences, which differed significantly between species. Within species, variation in food choice was similar among individuals. This indicates that snail populations may be composed of polyphagous individuals with similar food preferences. Different lichen species were of different net food quality to the snails as indicated by growth rate differences. In both snail species the most preferred lichen species of the choice experiment caused the largest weight increase in juveniles, viz. Caloplaca flavovirescens for C. clienta and Aspicilia calcarea for B. perversa. This suggest that the snail species studied differ in their abilities to deal with secondary compounds and physical characteristics of certain lichens or that they can utilize the energy and nutrients of these lichens to a different extent. It is suggested that differential food preferences might reduce the intensity of interspecific competition for resources (lichens) between C. clienta and B. perversa.

Keywords: Gastropoda - lichen grazing - food preference - secondary compounds - interspecific competition

1994  Interpopulation variation in propensity for egg cannibalism in the land snail Arianta arbustorum — Baur B — Animal Behaviour 48: 851–860   doi> 10.1006/anbe.1994.1309 
Artikel als pdf Datei herunterladen

Under natural conditions hatchlings of the land snail Arianta arbustorum cannibalize unhatched sibling eggs. Newly hatched A. arbustorum from different populations (from a lowland forest, a subalpine forest and an alpine pasture in Switzerland) differed significantly in the frequency of cannibalistic attacks on conspecific eggs. The percentage of cannibalistic hatchlings ranged from 50.0% in a subalpine forest to 87.8% in a lowland forest. Two populations were consistent in the proportion of cannibalistic hatchlings over 3 years, while in a third population the proportion of cannibalistic hatchlings varied between years. Hatchlings from populations with a high frequency of cannibals also began to eat eggs at an earlier age. In two populations, the proportion of cannibalistic hatchlings per batch increased over the course of the season, while in a third population the proportion of cannibals per batch was constantly high. Propensity for egg cannibalism was not correlated with absolute egg size, suggesting that the amount of energy and nutrients received during embryonic development did not affect cannibalistic behaviour during the hatchling stage. Differences in the investment in single eggs could explain the inter-population variation in propensity for egg cannibalism in A. arbustorum.

Keywords: natural-populations - alpine populations - kin selection - clutch size - growth-rate - pulmonata - helicidae - proximate

1994  Multiple paternity and individual variation in sperm precedence in the simultaneously hermaphroditic land snail Arianta arbustorum — Baur B — Behavioral Ecology and Sociobiology 35: 413–421   doi> 10.1007/BF00165844 

Intraspecific variation in the proportion of offspring sired by the second mate with a female (P2) is an aspect of sperm competition that has received little attention. I examined the effects of delay between copulations (range 9-380 days) and size of sperm donor on sperm precedence in double-mated individuals of the simultaneously hermaphroditic land snail Arianta arbustorum. Using shell colour as a genetic marker, paternity was analysed in 132 broods produced by 35 snails that had mated with two partners of different genotype. Sperm precedence (P2) was influenced by the time between the two matings when the mating delay exceeded 70 days (one reproductive season). P2 averaged 0.34 in the first brood of snails that mated twice within 70 days indicating first mate sperm precedence. In contrast, P2 averaged 0.76 in broods of snails that remated in the following season, indicating a decreased viability of sperm from the first mate. The size of sperm-donating individuals had no effect on the fertilization success of their sperm in the first brood produced after the second copulation. Analysis of long-term sperm utilization in 23 snails that laid three to nine egg batches over 2 years revealed striking differences among individuals. Five snails (21.7%) exhibited first-mate sperm precedence throughout, eight snails (34.8%) showed second-mate sperm precedence throughout, whereas ten snails (43.5%) exhibited sperm mixing in successive batches. It is suggested that the individual variation in sperm precedence in A. arbustorum may partly be due to differences in the amount of sperm transferred. Paternity analysis in 34 batches laid by 19 wild-caught individuals of A. arbustorum indicated that at least 12 snails (63.2%) used sperm from two or more mates for the fertilization of their eggs. This suggests a high incidence of multiple paternity is broods of A. arbustorum under field conditions.

Keywords: sperm precedence - multiple paternity - remating interval - mate size - gastropods

1994  Parental care in terrestrial gastropods — Baur B — Experientia 50: 5–14   doi> 10.1007/BF01992042 

Parental care in terrestrial gastropods includes the of oviposition sites, production of large, heavily-yolked eggs supplied with calcium carbonate, provisioning of hatchings with eggs in species with facultative sibling cannibalism, egg retention, and ovoviviparity. Evidence for true viviparity is scarce in terrestrial gastropods, as it is for postlaying care of eggs, though external egg carrying on the shell occurs in a few species. Care of young has not been observed in any terrestrial gastropod species. Provisioning of eggs with nutrients and calcium carbonate might be the most common form of parental investment. Ovoviviparity allows terrestrial gastropods to persist in habitats otherwise unsuitable for oviparous species (e.g. exposed rock walls). An interspecific comparison demonstrates that egg-retaining and ovoviviparous species produce smaller clutches than oviparous species and suggests a cost of parental care.

Keywords: parental investment - juvenile survival - evolution - gastropods - molluscs - ovoviviparity - viviparity

1993  Climatic warming due to thermal radiation from an urban area as possible cause for the local extinction of a land snail — Baur B & Baur A — Journal of Applied Ecology 30: 333–340   doi> 10.2307/2404635 

1. A field survey revealed that the land snail Arianta arbustorum had become extinct at 16 (55.2%) out of 29 localities in the surroundings of Basel (Switzerland) between 1908 and 1991. Habitat destruction by urban development was the reason for extinction of eight local snail populations. However, A. arbustorum also became extinct at eight localities, which were covered by vegetation suitable for the species and which still supported abundant populations of other helicid snail species including Cepaea nemoralis (all of them recorded in 1906-8).
2. Localities where A. arbustorum persisted and localities where it went extinct did not differ in exposure, inclination, percentage of woody plant cover, height of ground vegetation, distance to the nearest water body and number of other helicid snail species present. However, localities retaining A. arbustorum were situated on average at higher altitude than localities where it went extinct.
3. Remote sensing was used for mapping the surface temperature in the surroundings of Basel. During summer (when snail eggs were deposited) the surface temperature of the vegetation was significantly higher at localities where A. arbustorum went extinct compared to localities where the species still occurred. The surface temperature of the vegetation extracted from the satellite imagery was significantly correlated with the mean maximum temperature recorded in situ in potential oviposition sites of A. arbustorum at weekly intervals during summer 1992. The satellite imagery showed that built-up areas (central business district and industrial areas) affect adjacent vegetation areas by emitting thermal radiation. This suggests that local climatic warming due to extensive urban development might have caused the extinction of A. arbustorum populations.
4. One possible mechanism might be that egg development of A. arbustorum is sensitive to high temperature; embryos die if the ambient temperature exceeds a specific threshold. To test this hypothesis, we incubated eggs of A. arbustorum and C. nemoralis in the laboratory at 19, 22, 25 and 29 °C. Hatching success for eggs of A. arbustorum decreased from 81.5% at 19 °C to 38.7% at 22 °C, and no eggs hatched at higher temperatures. In contrast, eggs of C. nemoralis had a significantly higher hatching success than eggs of A. arbustorum at 22 and 25 °C. A second experiment demonstrated that exposure to 25 or 29 °C for only 24 h was enough to lower significantly the hatching success of A. arbustorum eggs.
5. These results suggest that temperature tolerance in egg development can determine the distribution of a snail species and, in case of climatic warming, cause its extinction.

Keywords: extinction - gastropods - climate change - temperature tolerance - thermal radiation

1993  Daily movement patterns and dispersal in the land snail Arianta arbustorum — Baur A & Baur B — Malacologia 35: 89–98

The relationship between daily movements of individuals and their dispersal over longer periods was studied in two natural populations of the land snail Arianta arbustorum in Switzerland. In a forest clearing, daily movements of individually marked snails ranged from 0 to 4.44 m (median 0.58 m); the frequency distribution of the distances traveled fitted a function with exponential decay. The snails showed no preference in direction of movement. Further, the directions chosen by an individual on consecutive days were independent from each other. These findings agree with the assumptions of a random movement model. In a 1-m wide belt of tall grass and forbs along a ditch, daily movements of A. arbustorum were exponentially distributed and ranged from 0 to 1.57 m (median 0.40 m). The snails' movements were confined to favourable vegetation; individuals that reached the edge of the belt did not enter the drier surroundings (a mown meadow); instead they continued to move in a new direction within the belt. Using characteristics of the movement pattern of the A. arbustorum population in the forest clearing, we simulated snail dispersal in habitats of different shape over longer periods. The simulations showed that snails dispersed significantly longer distances in a two-dimensional habitat than in linear habitats of 1 and 8 m width. A comparison with literature data on helicid snails dispersing in two-dimensional habitats (meadows, pastures) and linear habitats (roadside verges, river embankments, hedges) supports this result.

Keywords: limax-pseudoflavus evans - theba-pisana mollusca - alpine populations - cepaea-nemoralis - pulmonate slug - life-history Gastropoda - Helicidae - temperature - migration

1993  Do pioneers have r-selected traits? Life-history patterns among colonizing terrestrial gastropods — Bengtsson J & Baur B — Oecologia 94: 17–22   doi> 10.1007/BF00317295 

We examine whether pioneer species of terrestrial gastropods (snails and slugs) possess particular life history traits commonly associated with r-selection, using data on gastropod colonization in four areas in north-west Europe (the Kvarken and Tvärminne archipelagos in the Baltic, polder woods in IJsselmeer, and a rehabilitated quarry near Maastricht). Data on age at first reproduction, longevity, clutch size, egg size and lifetime fecundity were gathered from the literature. In order to control for potentially confounding effects of body size on life history traits, we compared the residuals from the allometric relations between life history traits and body size for pioneers and non-pioneers. In snails, all life history traits examined were related to body size. In slugs, all traits except age at first reproduction scaled with body size. Body sizes did not differ between pioneers and non-pioneers in any area. In all four areas, there were no significant differences between pioneers and non-pioneers in any of the life history traits examined, after body size had been taken into account. This indicates that pioneer terrestrial gastropods generally cannot be regarded as r-selected. Pioneer species may possess any of several life history strategies, and the combinations of traits shown by them may have little in common with the r-K selection concept.

Keywords: Mollusca - pioneers - life history - colonizing ability - r-selection

1993  Genital dimorphism in natural populations of the land snail Chondrina clienta and the influence of the environment on its expression — Baur B, Chen X & Baur A — Journal of Zoology 231: 275–284   doi> 10.1111/j.1469-7998.1993.tb01917.x 

Several species of simultaneously hermaphroditic land snails show a genital dimorphism: aphallic individuals differ from euphallic ones by a lack of male copulatory organs (penis plus genital retractor muscle). Aphallic individuals can self-fertilize or outcross as females but not as males. Thus, the mating system of a population may be significantly influenced by the proportion of aphallic individuals. We present data on the frequency of aphally in 23 natural populations of the rock-dwelling land snail Chondrina clienta on the Baltic island of Oland, Sweden. The populations varied greatly in percentage of aphallic individuals, ranging from 52.2 to 99.1%. (grand mean 77.7%). This variation did not follow any geographical pattern. In a laboratory experiment, we examined whether food supply (high or low) and/or population density (high or low) experienced during ontogeny affected the expression of genital dimorphism. Snails derived from a population with 99.1% aphallic individuals and raised under different food and density conditions did not differ from the original population in frequency of aphally. By contrast, when snails from a population with 66.7% aphallic individuals were raised on a low food supply, more individuals became euphallic than expected under complete genetic determination. These results suggest that, in addition to a genetic component, the expression of the genital dimorphism can be influenced by environmental conditions.

Keywords: Balea perversa - hermaphrodite - reproduction - Planorbidae - growth

1993  Genital dimorphism in the land snail Chondrina avenacea: frequency of aphally in natural populations and morph-specific allocation to reproductive organs — Baur B & Chen X — The Veliger 36: 252–258

Several species of simultaneously hermaphroditic land snails show a genital dimorphism: aphallic individuals differ from euphallic ones by a lack of male copulatory organs (penis and genital retractor muscle). Aphallic individuals can self-fertilize or outcross as females but not as males. Thus, the mating system of a population may be significantly influenced by the proportion of aphallic individuals. We present data on the frequency of aphally in 21 natural populations of the rock-dwelling land snail Chondrina avenacea in the surroundings of Basel, Switzerland. The populations varied greatly in percentage of aphallic individuals, ranging from 0.9 to 89.2% (grand mean 41.2%). This variation did not follow any discernible geographical pattern. The proportion of aphallic snails within a population was influenced neither by local population density nor by any other habitat characteristics - (exposure of rock face, altitude of locality, number of other snail species present). The populations varied significantly in adult shell size. Within populations, aphallic individuals tended to be smaller than euphallic ones. After controlling for size differences, the reproductive organs amounted to 28.3% of the total body mass in aphallic snails and to 31.7% in euphallic snails in a population. This difference can be explained by the absence/presence of male copulatory organs, whose dry weight was 3.2% of the total body mass of euphallic individuals. Monthly sampling of snails from one population revealed that individuals of Chondrina avenacea did not change their sex type over the course of one year.

Keywords: dimorphism - sex allocation - habitat - frequency - seasonal variation - hermaphroditism - self fertilization - Switzerland - Europe - Gastropoda - Mollusca - Invertebrata

1993  Intraclutch egg cannibalism by hatchlings of the land snail Arianta arbustorum: non-random consumption of eggs? — Baur B — Ethology Ecology & Evolution 5: 329–336   doi> 10.1080/08927014.1993.9523020 

Under natural conditions hatchlings of the land snail Arianta arbustorum cannibalize unhatched sibling eggs as well as eggs from neighbouring batches. Three series of choice experiments were conducted to determine whether cannibalistic hatchlings of A. arbustorum from four different populations discriminate (1) between fertilized and unfertilized eggs within the same batch, (2) between eggs containing well-developed embryos and ones with less advanced embryos, and (3) between small and large fertilized eggs. Newly-hatched snails did not discriminate between fertilized and unfertilized conspecific eggs. Similarly, hatchlings cannibalized in equal proportions eggs with well-developed embryos and eggs with less advanced embryos. However, cannibalistic hatchlings ate preferentially large eggs. The results of an additional choice experiment indicated that this size preference may be due to a higher encounter probability and/or a stronger attraction by chemical cues of larger eggs, and thus is not an actual choice made by the cannibalistic hatchling. It is suggested that the higher susceptibility of large eggs to cannibalism may act as selection pressure against increasing egg size.

Keywords: behavior - evolution - cannibalism - snail - Gastropoda - Pulmonata - Arianta arbustorum

1993  Number and size of oocytes in relation to body size and time of day in the kleptoparasitic bee Nomada lathburiana (Hymenoptera: Anthophoridae) — Tengö J & Baur B — Entomologia Generalis 18: 19–24   doi> 10.1127/entom.gen/18/1993/19 

The relationships between the number of oocytes, size of oocytes, and body size were examined in a population of the kleptoparasitic bee Nomada lathburiana (Kirby 1802) in Central Sweden. Most females have 5 ovarioles in each ovary with an average of 17.3 mature and nearly mature oocytes in both ovaries. The number and size of mature and nearly mature oocytes increase with bee body size. Females collected at different times of day do not differ in oocyte number. The size-related fecundity in N. lathburiana might be of adaptive significance not only by the enhanced capacity to lay more eggs, but also by the production of larger larvae which may enjoy an increased survivorship.

Keywords: fecundity - oocyte size body size relationship - oocyte number - ovariol number - kleptoparasitic bee - Nomada lathburiana - Anthophoridae

1993  The effect of multiple mating on female reproductive success in the simultaneously hermaphroditic land snail Arianta arbustorum — Chen X & Baur B — Canadian Journal of Zoology 71: 2431–2436   doi> 10.1139/z93-339 

The simultaneously hermaphroditic land snail Arianta arbustorum mates several times in the course of a reproductive season. Repeated matings might be adaptive for the male function of A. arbustorum to inseminate several "females." We designed an experiment to evaluate the effects of repeated mating on the female reproductive success of this hermaphrodite. Reproductive traits and survival were examined over 2 years in individuals that copulated several times per year (snails were kept in pairs), in individuals that copulated twice (once at the beginning of each year) or once (at the beginning of the first year only), and in individuals prevented from copulating (they were kept isolated). Copulations were not always reciprocally successful: 3 of 57 snails (5.3%) failed to produce fertile eggs, although their mates reproduced successfully. Similarly, 2 of 15 pairs (13.3%) failed to reproduce successfully. Snails allowed to mate repeatedly within each season tended to lay more eggs than snails that mated once per year. However, the numbers of hatchlings did not differ significantly between the two treatment groups, because eggs laid by snails allowed to mate repeatedly had a lower hatching success. Snails that remated in the second year laid more eggs that had higher hatching success, and thus produced more hatchlings than snails that mated once at the beginning of the first year only. Snails that were prevented from mating produced a few hatchlings (by self-fertilization) in the second year; their reproductive success was less than 1% of that of mated snails. Our results suggest that multiple mating is also adaptive for the female function of A. arbustorum by increasing female fecundity and fertility and serving as a hedge against unsuccessful copulations.

1992  Effect of courtship and repeated copulation on egg production in the simultaneously hermaphroditic land snail Arianta arbustorum — Baur B & Baur A — Invertebrate Reproduction and Development 21: 201–206   doi> 10.1080/07924259.1992.9672239 

An experiment was conducted to examine whether extended courtship display (a major component of mating behaviour) or repeated copulation in the course of a reproductive season stimulates egg production in the simultaneously hermaphroditic land snail Arianta arbustorum. Repeated copulation was found to increase the number of eggs produced while courtship display did not appear to affect egg production. However, repeated copulation neither accelerated the onset of egg laying nor increased the hatching success of eggs. These results suggest that reciprocal intromission and/or receipt of a spermatophore, but not the long-lasting courtship behaviour, stimulates egg production in A. arbustorum.

Keywords: Arianta arbustorum - courtship - egg production - Gastropoda - repeated copulation - simultaneous hermaphrodite - Stylommatophora

1992  Random mating by size in the simultaneously hermaphroditic land snail Arianta arbustorum: experiments and an explanation — Baur B — Animal Behaviour 43: 511–518   doi> 10.1016/S0003-3472(05)80109-5 
Artikel als pdf Datei herunterladen

It has been proposed that size-assortative mating should occur in simultaneous hermaphrodites with reciprocal fertilization and size-related fecundity because all individuals invest substantially in mating. Mating patterns were recorded in two species of simultaneously hermaphroditic land snails. In a natural population of Helix pomatia, snails showed a slight (but non-significant) tendency towards size-assortative mating, whereas mating in a population of Arianta arbustorum was random with respect to size. Laboratory experiments were conducted to test (1) whether individuals of A. arbustorum discriminate between mating partners of different size, and (2) whether a large shell might be of advantage during courtship to increase mating success. In mate-choice tests with individuals of different shell size, pairs formed randomly with respect to size. Courtship was neither hindered nor prolonged in pairs with large size differences. In the second experiment, a large snail was placed close to two courting conspecifics (both smaller). The larger snail interfered with the courting snails, but in general did not displace one of them. Courtship progressed to copulation only if one of the three snails ceased to court; this was independent of the size of that individual. Thus, a large shell did not increase mating success. It is suggested that time-constraints of locomotory activity and high costs of searching for a mate can explain the prevalence of random mating patterns in simultaneously hermaphroditic land snails.

Keywords: Helix aspersa - terrestrial gastropods - behavior - temperature - courtship - helicidae - pulmonata - patterns - density

1992  Reduced reproductive compatibility in Arianta arbustorum (Gastropoda) from distant populations — Baur B & Baur A — Heredity 69: 65–72   doi> 10.1038/hdy.1992.95 

Reproductive isolation was examined in the simultaneously hermaphroditic, self-incompatible land snail Arianta arbustorum. We tested individuals from two geographically isolated populations in Sweden and three populations in Switzerland. In mate-choice tests, within-population (homotypic) and between-population (heterotypic) meetings occurred among snails in frequencies expected by chance. We found no significant difference in courtship latency and courtship duration between homotypic and heterotypic pairs. However, snails from three populations preferred to mate with homotypic partners. Mating preferences could partly be explained by differences in mating propensity in two out of three populations, but not in matings between a Swedish and a Swiss population. Cross breeding demonstrated a high degree of reproductive compatibility between these two distant populations. In contrast, heterotypic pairs involving two Swiss populations had a reduced fertility. The experimental results indicate that partial premating and postmating isolation may exist between distant populations of A. arbustorum. However, the degree of isolation is not related to the geographical distance between populations.

Keywords: courtship - fecundity - gastropod - isolation - mate choice - reproductive compatibility

1992  Responses in growth, reproduction and life span to reduced competition pressure in the land snail Balea perversa — Baur A & Baur B — Oikos 63: 298–304

Intraspecific interactions early in an individual's life may lead to reduced reproduction once maturity is attained. Possibly, this could be compensated by increased or prolonged reproduction later in life if competition is relaxed (i.e. after a sudden decrease in population density as the result of a catastrophic event). We tested this compensation hypothesis in the ovoviviparous, self-fertilizing land snail Balea perversa (L.). Age and size at first reproduction, as well as reproductive output, were influenced by the initial experimental density; individuals kept at high density reached sexual maturity late and at a small size. In the relaxation period, reproductive rate did not differ between snails from different initial densities. Individuals initially kept at high population density lived longer during the relaxation period than ones kept at low density. Nevertheless, they did not live long enough to compensate for the earlier loss in fecundity; overall reproductive life span and lifetime fecundity decreased with increasing initial density.

1992  The effect of lichen diet on growth rate in the rock-dwelling land snails Chondrina clienta (Westerlund) and Balea perversa (Linnaeus) — Baur A, Baur B & Fröberg L — Journal of Molluscan Studies 58: 345–347   doi> 10.1093/mollus/58.3.345 

Keywords: feeding preference - Cyanobacteria - Lichenes - growth - feeding - bacteria - Thallophyta - Gastropoda - Mollusca - Invertebrata

1991  The effect of hibernation position on winter survival in the rock-dwelling land snails Chondrina clienta and Balea perversa on Öland, Sweden — Baur A & Baur B — Journal of Molluscan Studies 57: 331–336   doi> 10.1093/mollus/57.3.331 

The effect of hibernation position on winter survival was examined for four years in the rock-dwelling land snails Chondrina chenta and Balea perversa inhabiting exposed stone walls on the Baltic island of Öland, Sweden. Individuals of both species hibernated either singly or aggregated in groups, attached to the lower surface of horizontally arranged pieces of limestone. B. perversa hibernated more frequently in aggregations than did C. clienta, and in both species adults occurred more frequently in aggregations than did juveniles. For both age classes of C. clienta in winter 1987/88 and for juveniles of B. perversa in 1988/89, individuals that hibernated in large aggregations had a higher survival rate than individuals hibernating singly or in small aggregations. No differential survival with respect to hibernation position was found in the winter of 1986/87 when the lowest temperatures were recorded (minimum temperature -16.4 degree-C). During this extremely cold winter mean survival rates of 33.9% were recorded for C. clienta and 73.3% for B. perversa. The succeeding three winters were mild, with mean survival rates of 83.2% in C. clienta and 91.1% in B. perversa. In both species adults had a higher survival rate than juveniles. After a period of extreme cold (-16 degree-C) survival of C. clienta inhabiting a snow-covered pile of stones was significantly higher than that of conspecifics on a snow-free stone wall, suggesting that snow cover has an insulating effect.

Keywords: reproduction - growth - size

1990  Andrena wilkella male bees discriminate between enantiomers of cephalic secretion components — Tengö J, Ågren L, Baur B, Isaksson R, Liljefors T, Mori K, König W & Francke W — Journal of Chemical Ecology 16: 429–441   doi> 10.1007/BF01021775 

Diastereomers of the spiroacetal, 2,8-dimethyl-1,7-dioxaspiro [5.5]undecane, represent main components of the cephalic secretion from males of the solitary bee, Andrena wilkella. The major compound proved to be of high enantiomeric purity, showing (2S,6R,8S) configuration. Only the naturally occurring enantiomer attracted patrolling males in the field; its antipode was behaviorally inactive and in a racemic mixture did not inhibit response. The (E,Z) diastereomers were also found to be almost inactive. EAG studies gave the same result as the behavioral tests. The biological function of the spiroacetal is discussed in view of the evolution of the mating behavior in A. wilkella.

Keywords: enantiomer discrimination - male patrolling - odor marking - Hymenoptera - Apoidea - Andrena wilkella - bee - EAG - spiroacetal - absolute configuration - 2,8-dimethyl-1,7-dioxaspiro[5.5]undecane

1990  Are roads barriers to dispersal in the land snail Arianta arbustorum? — Baur A & Baur B — Canadian Journal of Zoology 68: 613–617   doi> 10.1139/z90-091 

The effect of road width on dispersal in the land snail Arianta arbustorum was examined by recording displacements of marked individuals during one activity season (3 months) in central Sweden. For two sites, a paved road (8 m wide, low traffic density) and an unpaved track (3 m wide), the snails' movements were largely confined to roadside verges. The snails followed the vegetation belts; the average displacements ranged from 1.5 to 4.9 m at different sites. Several snails covered large distances, the maximum recorded being 14 m. Despite these long-distance dispersers, only one of the recaptured snails crossed the paved road and two crossed the track, indicating that the road and, to a minor extent, the track acted as dispersal barriers. By contrast, an overgrown path (0.3 m wide) did not influence the snails' movement. Our results suggest that snail populations separated by paved roads with high traffic densities may be isolated from each other.

1990  Possible benefits of egg cannibalism in the land snail Arianta arbustorum (L.) — Baur B — Functional Ecology 4: 679–684   doi> 10.2307/2389736 

Hatchlings of the land snail Arianta arbustorum (L.) were used to test whether the ingestion of conspecific eggs confers nutritional advantages to a cannibal in terms of increased growth rate and survival. In the field, hatchlings of A. arbustorum consume unhatched sibling eggs as well as eggs from neighbouring batches. In a laboratory experiment, 20 newly hatched sibling snails from each of 24 egg batches were divided into two groups and fed either conspecific eggs or lettuce for 10 days. Growth during this period was recorded, as well as subsequent growth and survival to maturity. During this latter period the animals of both groups were kept under identical conditions and fed on lettuce. Hatchlings fed a cannibalistic diet during their first 10 days of life experienced an increase in wet weight 2.6 times as high as those fed on lettuce. Diet did not affect hatchling survival, but it did influence future survival: 66.6% of the individuals initially fed on eggs attained adulthood compared to 38.0% of those fed on lettuce. Cannibalistic hatchlings tended to complete shell growth more rapidly and thus became mature earlier than non-cannibalistic ones, but the two groups did not differ in adult shell size. Thus, a cannibalistic diet during the hatchling stage will give accelerated growth and higher survival.

1990  Seasonal changes in clutch size, egg size and mode of oviposition in Arianta arbustorum L. (Gastropoda) from alpine populations — Baur B — Zoologischer Anzeiger 225: 253–264

Keywords: seasonal variation - reproduction - egg laying - clutch size - Alps - Europe - Gastropoda - Mollusca - Invertebrata

1989  Absence of isozyme variation in geographically isolated populations of the land snail Chondrina clienta — Baur B & Klemm M — Heredity 63: 239–244   doi> 10.1038/hdy.1989.97 

Genetic differentiation of the rock-dwelling land snail Chondrina clienta was examined by enzyme electrophoresis in five isolated populations of an outlying area (the Baltic island of Öland, Sweden), and in one population from the species' main range (eastern Alps, Austria). Patterns of allelic variation were compared for 17 putative gene loci involving ten protein systems. All individuals from the five isolated populations on Öland were identically homozygous at all gene loci assayed. Snails from the eastern Alps were homozygous and allelically identical, but they differed by one isozyme band that was absent in animals from Öland and by different alleles fixed at three loci. The absence of isozyme variation and anatomical evidence indicate that self-fertilization may be the prevailing type of reproduction in C. clienta. The allelic identity of the five populations on Öland suggests that they were derived from a single strain, the origin of which probably consisted of one or few self-fertilizing individuals which colonized the island.

Keywords: reproductive isolation - polymorphism - Gastropoda - enzyme - isozyme - geographical variation - genetic variability - island - gel electrophoresis - homozygozity - self fertilization - mating system - population genetics - Mollusca - Invertebrata

1989  Growth and reproduction of the minute land snail Punctum pygmaeum (Draparnaud) — Baur B — Journal of Molluscan Studies 55: 383–387   doi> 10.1093/mollus/55.3.383 

Reproductive characters and growth of Punctum pygmaeum were investigated under laboratory conditions. Eggs were laid singly at intervals of 2-8 days. Egg size averaged 0.41 by 0.50 mm. Due to a variable period of egg retention, newly deposited eggs contained differently developed embryos resulting in an incubation period varying from 1 to 34 days. Each snail on average laid 6.0 eggs (range 1-16 eggs) during its life. Egg production rate and hatching success in individuals kept in isolation were the same as in individuals kept in pairs. Hatchlings measured 0.49 mm in shell breadth. Snails grew throughout their life, but the growth rate declined significantly at a shell breadth of 1.3-1.4 mm, the point at which the onset of sexual maturity occurred. Comparison of reproductive characters of snails living in leaf litter revealed that very small-sized species produce few, but in relation to their shell size large eggs, which they oviposit singly.

1988  Do the risks of egg cannibalism and desiccation influence the choice of oviposition sites in the land snail Arianta arbustorum? — Baur B — Journal of Zoology 216: 495–502   doi> 10.1111/j.1469-7998.1988.tb02445.x 

Laboratory tests were conducted to examine whether egg-laying Arianta arbustorum prevents egg cannibalism in its offspring by the choice of oviposition sites. Arianta arbustorum did not react to the presence of conspecific eggs when starting to oviposit, thus exposing its eggs to the risk of between-batch cannibalism. Snails preferred to oviposit in soil of higher moisture content even at high air humidity, reducing the risks of later egg desiccation and within-batch cannibalism. Both the types of oviposition sites chosen and their spatial distribution, as observed in 11 natural populations of A. arbustorum near Uppsala, Sweden, suggest that abiotic factors, such as a permanently moist microhabitat, may exert a stronger selection pressure on the oviposition-site choice than does between-batch egg cannibalism.

Keywords: cannibalism - desiccation - oviposition - site selection - Arianta arbustorum

1988  Egg-species recognition in cannibalistic hatchlings of the land snails Arianta arbustorum and Helix pomatia — Baur B — Experientia 44: 276–277   doi> 10.1007/BF01941738 

Laboratory experiments were conducted to determine whether cannibalistic hatchling of the land snails Arianta arbustorum and Helix pomatia discriminate between eggs of the two species. Hatchlings from both species showed a significant choice for conspecific eggs and consumed on average 1 egg in 4 days. Eggs from the other species were only occasionally eaten.

Keywords: choice - recognition - cannibalism - predation - gastropods - pulmonates

1988  Life history of the land snail Arianta arbustorum along an altitudinal gradient — Baur B & Raboud C — Journal of Animal Ecology 57: 71–87

(1) The life history of the polymorphic land snail Arianta arbustorum was investigated in live natural populations along an altitudinal gradient from 1220 to 2600 m in the Swiss Alps. In order to assess the environmentally-induced variation of reproductive characters snails were transplanted to the lowlands.
(2) Adult size decreased from 19.9 to I6.0 mm (mean shell breadth) with increasing altitude, age at maturity increased from 1.9 to 5.0 years, but median adult longevity and adult survival rates were approximately the same at all altitudes.
(3) Clutch number, clutch size, egg size and reproductive investment per year decreased with increasing altitude in resident snails, whereas reproductive investment per egg increased. Within populations, clutch number, number of eggs produced per year and egg size scaled allometrically with shell size indicating a size-specific fecundity.
(4) Transplanted snails laid 1.3-11.5 times more clutches than did resident snails. However, no differences in clutch size, egg dry weight and hatching success were found between transplanted and resident snails, except in one population, in which transplanted snails laid smaller clutches with larger eggs and scored a lower hatching success.
(5) Transplanted snails were less variable in reproductive characters than resident ones, except for hatching success.
(6) In general, life-history characters did not appear to be correlated with shell or body colour.
(7) Although proximate factors like temperature explain most of the variation in life history, evidence was obtained also for genetic divergence among populations. The results match the predictions of the adversity selection model well, rather than those of bet-hedging or r/K-selection.

1988  Microgeographical variation in shell size of the land snail Chondrina clienta — Baur B — Biological Journal of the Linnean Society 35: 247–259   doi> 10.1111/j.1095-8312.1988.tb00469.x 

Microgeographical variation in shell morphology of the rock-dwelling land snail Chondrina clienta, collected from 30 sites within an area of 0.5 km2 on the island of Öland, Sweden, was examined in relation to its own population density and that of a potential competitor (the land snail Balea perversa) and to environmental factors. Dispersal of marked individuals averaged 83 cm per year within a stone pile and 291 cm in an area of exposed bedrock. Local population density of active C. clienta ranged from 5 to 794 individuals per m2. Shell characters were highly intercorrelated, both within and between populations. Principal component analysis revealed that most of the interpopulational variation could be expressed by the single character of shell height, which ranged from 5.54 to 6.94 mm. In all populations, snails of a given size had the same whorl number. Shell size was not influenced by habitat type (exposed rock surface, stone pile or stone wall) or proportion of calcareous stones within habitat. It was, however, negatively correlated with local population density, indicating intraspecific competition, and positively correlated with the degree of plant cover within the habitat. Analysis of variance revealed additionally a density effect of B. perversa on shell size in C. clienta, probably as a result of interspecific competition. Breeding experiments using C. clienta from different sites and carried out under uniform conditions caused most of the phenotypic variation to disappear, demonstrating the high phenotypic plasticity of the species.

Keywords: adaptation - phenotypic plasticity - shell size - population density - competition - Gastropoda - Chondrinidae

1988  Population regulation in the land snail Arianta arbustorum: density effects on adult size, clutch size and incidence of egg cannibalism — Baur B — Oecologia 77: 390–394   doi> 10.1007/BF00378049 

The relationships between local population density and adult size, clutch size and spatial distribution of egg batches were investigated in 11 natural populations of the land snail Arianta arbustorum in a forest near Uppsala, Sweden. Shell size of adults decreased with increasing population density as did clutch size. Within populations, clutch size scaled allometrically with shell size indicating size-specific fecundity. It is hypothesized that food unpalatability caused by mucus deposition slows down juvenile growth rate in high density populations, resulting in small adults and thus reducing their fecundity in subsequent years. The influence of the distance between batches on the incidence of egg cannibalism by hatchlings was examined in a laboratory experiment. In this experiment the number of eggs cannibalized increased with decreasing distance to the batch of hatching snails. Thus, in the field, eggs of highly aggregated batches suffer a high risk of cannibalism. In the 3 populations with the highest snail density, 21-39% of all batches were deposited close to each other (nearest neighbour distance ≤5 cm, i.e. less than hatchlings more within 1 day). These findings indicate that egg cannibalism can act as a population regulating factor.

Keywords: population regulation - shell size - fecundity - cannibalism - gastropoda

1988  Repeated mating and female fecundity in the simultaneously hermaphroditic land snail Arianta arbustorum — Baur B — Reproduction and Development 14: 197–204   doi> 10.1080/01688170.1988.10510378 

To evaluate the influence of repeated mating on female fecundity in the simultaneously hermaphroditic, self-incompatible land snail Arianta arbustorum, the number and size of clutches, egg size and hatching success of individuals from 3 populations were determined under conditions of isolation and grouping during one breeding season in a field cage experiment. Only adult snails which had mated and oviposited in the preceding year were used.
Sperm storage enabled isolated individuals to continue with the production of fertilized eggs. Snails kept singly or in groups differed neither in number of clutches laid nor in egg size. But isolated snails laid smaller clutches than did grouped snails. As a result isolated snails produced fewer eggs per breeding season. Hatching success varied greatly between populations and rearing conditions. In general, isolated snails had fewer hatchlings than grouped snails, indicating that individuals prevented from remating suffered a reduced fitness.

Keywords: Arianta arbustorum - Gastropoda - hermaphrodite - repeated mating - sperm storage - fecundity - clutch size

1987  Colonizing ability in land snails on Baltic uplift archipelagos — Baur B & Bengtsson J — Journal of Biogeography 14: 329–341   doi> 10.2307/2844941 

We have examined correlates of land snail colonizing ability in two land uplift archipelagos in the Baltic, using literature data on the orders of colonization and on life histories, mating systems, habitat niche breadths, abundances and habitat requirements. No correlations between life history traits associated with the r-K-continuum and the orders of colonization could be found. Our results suggest that the availability of suitable habitats on islands partly, but not exclusively, determine the orders of colonization. Species with broader habitat niches were more abundant in the source areas, and tended to colonize islands earlier than habitat specialists. Information about mating systems suggests that self-fertilization is more common in colonizers than in non-colonizers. The importance of phenotypic plasticity and dispersal ability for colonizing ability is discussed, and it is concluded that colonization success cannot be predicted from life history traits commonly associated with r-selection.

1987  Effects of early feeding experience and age on the cannibalistic propensity of the land snail Arianta arbustorum — Baur B — Canadian Journal of Zoology 65: 3068–3070   doi> 10.1139/z87-465 

The influence of early feeding experience on egg cannibalism was examined in hatchlings of the land snail Arianta arbustorum. The propensity for cannibalism was not affected by cannibalistic or by vegetarian early feeding experience. It was, however, negatively correlated with the age of the snails. Freshly hatched snails with no prior feeding experience chose eggs exclusively, while 16-day-old snails preferred vegetable food. Furthermore, the cannibalistic propensity varied between offspring from different clutches. Restriction of the cannibalistic propensity to the hatchling stage, its nonmodifiability, and differences in its extent between clutches suggest that egg cannibalism in A. arbustorum is a genetically determined trait.

Keywords: cannibalism - diet - conditioning - young animal - age - intraspecific comparison - inheritance - laboratory study - feeding - Helicidae - Gastropoda - Mollusca - Invertebrata

1986  Geographic variation of resting behaviour in the land snail Arianta arbustorum (L.): does gene flow prevent local adaptation? — Baur B — Genetica 70: 3–8   doi> 10.1007/BF00123208 

The resting behaviour of the land snail Arianta arbustorum (L.) from different geographic areas in the eastern Swiss Alps was compared under uniform conditions in order to examine whether local populations had evolved adaptive differences. Differences were observed in resting site preferences of snails from different geographic provenances, which did not seem to be associated with any environmental variables. The observed patterns support the electrophoretic evidence from other studies that there is gene flow between geographically very close populations, above all, along streams. This gene flow may swamp incipient behavioural changes. Morphological differences in shell features, however, appear to take place in spite of gene flow.

1986  Patterns of dispersion, density and dispersal in alpine populations of the land snail Arianta arbustorum (L.) (Helicidae) — Baur B — Holarctic Ecology 9: 117–125   doi> 10.1111/j.1600-0587.1986.tb01200.x 

In studying populations of the land snail Arianta arbustorum in the eastern Swiss Alps, juvenile and subadult snails were found to be aggregated all the time, while adults were mostly aggregated during summer, the main mating period. The mean size of aggregations was 25 cm × 25 cm but varied, according to the area a grass tuft covered, while the intensity of aggregations was influenced by weather conditions. Densities of 10-15 subadults and 3-6 adults m² were found along ditches and streams, 2-25 subadults and 2-20 adults on uncultivated alpine meadows, while on scree-covered alpine grassland the density of subadults and adults was 0.3-0.5 m-2. The extent of daily movements varied with microclimatic factors and season and depended on the structure of the habitat. The dispersal rate was greatest in June (2.6 m month-1) and least in August (1.1 m month-1). In summer and autumn, active uphill movements were noted, a process which compensates for the loss of altitude by passive downhill displacements. Rolling down on snowfields and being carried away by avalanches and streams were observed.

1986  Proximate factors influencing egg cannibalism in the land snail Arianta arbustorum (Pulmonata, Helicidae) — Baur B & Baur A — Oecologia 70: 283–287   doi> 10.1007/BF00379252 

Factors affecting oophagy among siblings in the land snail Arianta arbustorum were studied in 3 populations from different altitudes in Switzerland. The degree of egg cannibalism in A. arbustorum is a function of hatching asynchrony since the earliest hatched snails will devour the unhatched eggs in the same clutch. Clutch size, egg density and amount of vegetable food available to newly hatched snails did not affect the degree of cannibalism. Snails from 3 populations were similar in terms of incubation time and intrinsic hatching asynchrony of the clutches. However, they differed in degree of cannibalism when the hatching asynchrony had been experimentally increased. Snails from a lowland forest showed a higher degree of cannibalism than did those from an alpine mountain slope. The parent snails differed in terms of incubation time and hatching synchrony in their clutches. Under natural conditions, the length of the hatching spread and, as a result, the degree of cannibalism will depend additionally on the mode of oviposition (batches or single; clumped or dispersed), on the spatial heterogeneity of egg-laying places and on climatic conditions (e.g. drought).

Keywords: Arianta - Pulmonata - egg cannibalism - oophagy - climate

1985  Causes of death and possible regulatory processes in Arianta arbustorum (L., 1758) (Pulmonata, Helicidae) — Reichardt A, Raboud C, Burla H & Baur B — Basteria 49: 37–46

Keywords: Gastropoda - mortality - predation - parasitism - interspecific competition - population regulation - Switzerland - Mollusca - Invertebrata

1984  Early maturity and breeding in Arianta arbustorum (L.) (Pulmonata: Helicidae) — Baur B — Journal of Molluscan Studies 50: 241–242

During field studies on the land snail Arianta arbustorum (L.) in the eastern Swiss Alps the authors repeatedly observed mating snails of which one snail was subadult while its partner was fully grown with a thickened lip. In four instances a record was kept. In one case the subadult snail had a bigger shell size than its adult partner, in the other cases the subadults were smaller. The mating snails from Weissbad and the subadult snail from Savognin were brought to the laboratory and kept isolated in transparent polythene boxes in natural daylight and at a temperature of 19-22 degree C. The subadult snail from Savognin laid 3 clutches of 12, 20 and 14 eggs, the subadult snail from Weissbad 2 clutches of 26 and 39 eggs. Compared with its adult mating partner, the subadult snail from Weissbad produced fewer and smaller eggs. On the other hand, the hatching rate of the subadult's eggs was higher. The present observations show that A. arbustorum is capable of reproducing while still subadult. Formerly, helicids were considered to be mature only when fully grown and with a thickened lip at the aperture of the shell.

1984  Shell size and growth rate differences for alpine populations of Arianta arbustorum (L.) (Pulmonata: Helicidae) — Baur B — Revue suisse de Zoologie 91: 37–46

Since in the Alps adult size of Arianta arbustorum (L.) tends to decrease with the altitude of the site, snails from high and low altitude were reared from egg to adulthood in the laboratory under identical conditions. The eggs were laid by snails that had been sampled from two mountain sites and the corresponding foot of the slopes. During ontogeny the shell diameter was measured weekly. Laboratory-reared snails from valley populations grew to the same size as snails from nature at the same sites, whereas laboratory-reared snails from mountain populations grew larger than their field counterparts. In the laboratory, A. arbustorum from mountain populations required more time to accomplish growth and had a smaller juvenile growth rate than snails from corresponding valley populations. Juvenile growth rate is positively correlated with adult shell diameter. Snails from valley populations lay larger eggs than snails from the mountains.

Keywords: body size - growth rate - ecological distribution - altitude - {Q2} - Arianta arbustorum