Ergänzende Informationen zu Publikationen von Sandro Meyer

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

For the restoration of biodiversity in agricultural grasslands, it is essential to understand how management acts as an ecological filter on the resident species. Mowing constitutes such a filter: only species that possess functional traits enabling them to withstand its consequences can persist in the community. We investigated how the timing of mowing modulates this filtering effect for insects. We predicted that two traits drive species responses. Species with larval development within the meadow vegetation will suffer more from mowing than species whose larvae develop in or on the ground, or outside the meadows, while species with a later phenology should benefit from later mowing. We conducted a five_year experiment, replicated at 12 sites across the Swiss lowlands, applying three different mowing regimes to low_intensity hay meadows: (1) first cut of the year not earlier than 15 June (control regime); (2) the first cut delayed until 15 July; and (3) leaving an uncut grass refuge on 10–20% of the meadow area (after earliest first cut on 15 June). Before the first cut in years 4 or 5, we sampled larvae of Lepidoptera and sawflies, and adults of moths, parasitoid wasps, wild bees, hoverflies, ground beetles, and rove beetles. Overall, before the first cut of the year, abundances of species with vegetation_dwelling larvae were higher in meadows with delayed mowing or an uncut grass refuge, with some taxon_specific variation. In contrast, species whose larval development is independent of the meadow vegetation showed no differences in abundance between mowing regimes. Species richness did not differ among regimes. For species with vegetation_dwelling larvae, a fourth_corner analysis showed an association between early phenology and the control regime. No associations were found for the other functional groups. Our results show that slight modifications of mowing regimes, easily implementable in agri_environmental policy schemes, can boost invertebrate abundance, potentially benefitting insectivorous vertebrates.

Keywords: cutting - ecological filter - fourth_corner analysis - grassland - invertebrates - mowing date - multiabundance - multidiversity

There is ongoing concern regarding the observed decline in pollinator populations. Managing agricultural landscapes through agri-environment schemes (AES) supports biodiversity and could counteract pollinator population declines. We investigated whether alterations to current AES grassland mowing regimes would increase the abundance and species richness of wild bees and hoverflies. Furthermore, we investigated the response of different nesting and feeding guilds of wild bees and hoverflies, respectively, to these regimes. The three experimental mowing regimes were: (i) first cut not before 15 June, before the beginning of summer (Swiss AES management, control meadows); (ii) first cut delayed until 15 July (delayed meadows); (iii) as for control meadows but leaving 10–20% uncut as a refuge (refuge meadows). The rationale behind the delayed and refuge mowing regimes was extending the availability of floral resources for pollinators, while also providing refugia for species that may be directly impacted by mowing. Hoverflies and wild bees were collected in 2014 and 2015, respectively, using pan-trapping and sweep-netting, once before and once after the first cut. The two collecting methods showed contrasting results. While there was no difference in the abundance or richness of wild bees between the meadows when using pan traps, following the first cut, sweep-netting resulted in a higher abundance and richness of wild bees in delayed and refuge meadows compared to control meadows. Pan-trapping detected a higher abundance of hoverflies in delayed compared to refuge meadows, whereas sweep-netting detected a higher abundance in delayed and refuge compared to control meadows, after the first cut. Saprophagous hoverflies were more abundant in the control and delayed than refuge meadows following the first cut, when sampled with pan traps. Predatory hoverflies were more abundant and species rich in delayed and refuge compared to control meadows following the first cut, when sampled by sweep-netting. Our study demonstrates that simple alterations to a common AES grassland mowing regime can enhance populations of pollinators and natural enemies of crop pests. Furthermore, the contrasting response of the life-history guilds indicates that promoting heterogeneous management practices within the landscape is important for supporting diverse communities, and maintaining key ecosystem services such as pollination and biocontrol.

Keywords: agri-environment schemes - biodiversity - ecosystem services - life-history traits - mowing - pollinators - semi-natural grassland