Data from: Species-habitat networks reveal key habitats for landscape-level wild bee conservation

Most agricultural landscapes are composed of a variety of habitats. A
landscape perspective is needed to understand biodiversity decline, but
many studies focus on single habitat types. In addition, the use of local
resources by species within and across habitats implies that species and
their habitats are linked in species-habitat networks. However, studies on
these networks are scarce. Here we used grid-based sampling to assess wild
bees at 224 sampling locations across all major habitat types, i.e.,
arable land, grassland, forest and orchard, in 14 differently composed
agricultural landscapes of Southern Germany. We assigned wild bees to
habitat types based on the dominant habitat cover surrounding their
sampling location to establish species-habitat networks and assessed how
these networks differed in modularity and robustness to habitat loss.
Orchards harbored more wild bees than expected based on their proportional
cover in the landscape, indicating a preference for this extensively
managed but threatened habitat by wild bees. Orchards also supported the
highest species richness and proportion of oligolectic wild bees, while
forests harbored the lowest richness and more social species. Landscape
diversity affected both structure and robustness of bee-habitat networks
in response to the simulated loss of habitats. Networks in more diverse
landscapes had higher modularity but tended to be less robust, showing
that greater landscape diversity and modularity do not necessarily buffer
against the effects of habitat loss. However, this effect appeared to be
mainly driven by increases in network size, as standardized modularity and
robustness (z-scores) were not affected by landscape diversity. We could
show that species-habitat networks are a powerful tool to inform
ecologists and policy makers about the importance of key habitats and
landscape diversity for species conservation. Key habitats for wild bee
conservation include extensively managed habitats like traditional
orchards. Nevertheless, all habitat types support a similar proportion of
endangered species, emphasizing the importance of a diverse landscape.
Conserving wild bees requires a variety of complementary habitats at the
landscape scale and must consider the management of traditional and
intensively managed habitats alike. Policy measures targeting landscape
diversity are urgently needed.