Semi-natural habitats provide important resources for wild bees in agricultural landscapes. Landscapes under management are dynamic and floral resources fluctuate in space and time. Thus, promoting different semi-natural habitat types within landscapes could be key to support diverse bee meta-communities throughout the season.
Here, we integrate analyses of α-diversity (species richness) and β-diversity and species-habitat networks to examine the relative contribution of all major semi-natural habitats to wild bee meta-communities in agricultural landscapes. We sampled extensively and conventionally managed meadows, flower strips, hedgerows and forest edges in spring, early and late summer in 25 landscapes in Switzerland.
Habitat types varied in their importance for wild bees throughout the season: While extensively managed meadows supported more rare species, habitat specialists and bee species overall than the other habitat types, flower strips were most important later in the season. Each of the five investigated habitat types harboured relatively unique sets of species with different habitats generally acting as distinct modules in the overall bee-habitat network.
Not only flower richness in a habitat per se, but also flower-habitat network properties (habitat strength and functional complementarity) were good predictors of wild bee richness. In addition to local floral richness, landscape composition and configuration interactively influenced β-diversity patterns across habitats.
Synthesis and applications. Our study highlights the value of pollinator-habitat network analysis to inform pollinator conservation management at the landscape scale, especially when combined with information on floral resources and flower-habitat networks. Maintaining different types of semi-natural habitats offers diverse and complementary resources throughout the season, which are crucial to sustain diverse wild bee meta-communities in agricultural landscapes. Particularly meadow extensification schemes can play a key role in safeguarding rare and specialist species in these landscapes. While locally a high flower richness promoted bee abundance and richness in general, our results indicate that increasing connectivity between habitat patches in landscapes dominated by arable crops appears to improve species exchange between local bee communities of different habitats, thereby possibly increasing their resilience to disturbances.