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Mass-flowering crops (MFCs) are increasingly cultivated and might influence pollinator communities in MFC fields and nearby semi-natural habitats (SNHs). Across six European regions and 2 years, we assessed how landscape-scale cover of MFCs affected pollinator densities in 408 MFC fields and adjacent SNHs. In MFC fields, densities of bumblebees, solitary bees, managed honeybees and hoverflies were negatively related to the cover of MFCs in the landscape. In SNHs, densities of bumblebees declined with increasing cover of MFCs but densities of honeybees increased. The densities of all pollinators were generally unrelated to the cover of SNHs in the landscape. Although MFC fields apparently attracted pollinators from SNHs, in landscapes with large areas of MFCs they became diluted. The resulting lower densities might negatively affect yields of pollinator-dependent crops and the reproductive success of wild plants. An expansion of MFCs needs to be accompanied by pollinator-supporting practices in agricultural landscapes.

1. Growing evidence for declines in wild bees calls for the development and implementation of effective mitigation measures. Enhancing floral resources is a widely accepted measure for promoting bees in agricultural landscapes, but effectiveness varies considerably between landscapes and regions. We hypothesize that this variation is mainly driven by a combination of the direct effects of measures on local floral resources and the availability of floral resources in the surrounding landscape. 2. To test this, we established wildflower strips in four European countries, using the same seed mixture of forage plants specifically targeted at bees. We used a before–after control–impact approach to analyse the impacts of wildflower strips on bumblebees, solitary bees and Red List species and examined to what extent effects were affected by local and landscape-wide floral resource availability, land-use intensity and landscape complexity. 3. Wildflower strips generally enhanced local bee abundance and richness, including Red-listed species. Effectiveness of the wildflower strips increased with the local contrast in flower richness created by the strips and furthermore depended on the availability of floral resources in the surrounding landscape, with different patterns for solitary bees and bumblebees. Effects on solitary bees appeared to decrease with increasing amount of late-season alternative floral resources in the landscape, whereas effects on bumblebees increased with increasing early-season landscape-wide floral resource availability. 4. Synthesis and applications. Our study shows that the effects of wildflower strips on bees are largely driven by the extent to which local flower richness is increased. The effectiveness of this measure could therefore be enhanced by maximizing the number of bee forage species in seed mixtures, and by management regimes that effectively maintain flower richness in the strips through the years. In addition, for bumblebees specificall

© 2015 Macmillan Publishers Limited. All rights reserved. There is compelling evidence that more diverse ecosystems deliver greater benefits to people, and these ecosystem services have become a key argument for biodiversity conservation. However, it is unclear how much biodiversity is needed to deliver ecosystem services in a cost-effective way. Here we show that, while the contribution of wild bees to crop production is significant, service delivery is restricted to a limited subset of all known bee species. Across crops, years and biogeographical regions, crop-visiting wild bee communities are dominated by a small number of common species, and threatened species are rarely observed on crops. Dominant crop pollinators persist under agricultural expansion and many are easily enhanced by simple conservation measures, suggesting that cost-effective management strategies to promote crop pollination should target a different set of species than management strategies to promote threatened bees. Conserving the biological diversity of bees therefore requires more than just ecosystem-service-based arguments.

Phylogenetically related species are assumed to be ecologically similar. Ecological similarity might lead to competition and to low distributional overlap. Therefore, if competitive interactions drive assemblages, we expect a decrease in distributional overlap with increasing phylogenetic relatedness and phylogenetic over-dispersion in assemblages. We tested this hypothesis by evaluating the mean phylogenetic distance of bat assemblages within grid cells of ≈36 km2 across Bavaria, Germany (887 grids; 20,023 records). To calculate phylogenetic distance between species, we used a phylogenetic tree derived from sequences of three mitochondrial genes (cytb, COI, ND1), two nuclear-protein-encoding genes (vWF, RAG2) and the genes encoding16S rRNA, 12S rRNA and tRNA-Val. Overall, bat species co-occurring within grid cells were more similar than expected from null models (phylogenetic clustering). This suggests that on the considered scale, bat assemblages are triggered more by environmental filters than by competition. Furthermore, mean phylogenetic distance decreased with the amount of anthropogenic habitats within grids. This contrasts with species richness of bats, which increased with anthropogenic habitats. Zusammenfassung Phylogenetisch verwandte Arten sind auch ökologisch ähnlich, was zu Konkurrenz führen kann. Wenn Konkurrenz eine Rolle spielt, dann erwartet man auch für phylogenetisch ähnliche Arten eine geringere Überlappung in ihrer Verbreitung sowie für Artengemeinschaften eine größere genetische Distanz als erwartet. Wir prüften diese Hypothese anhand der mittleren phylogenetischen Distanz von Fledermausgemeinschaften in Rasterquadraten Bayerns (≈36 km2; 887 Quadrate, 20.023 Datensätze). Zur Berechnung der phylogenetischen Distanz zwischen den Arten erstellten wir einen phylogenetischen Baum aus den Sequenzen von drei mitochondrialen Genen (cytb, CO1, ND1), zwei Kern-Protein-kodierenden Genen (vWF, RAG 2) und den Genen für 16sRNA, 12sRNA und