Does landscape mediate wild bee health and phylodiversity?

Landscape simplification negatively impacts bee communities and the pollination services they provide through loss of nesting and floral resources. Species rich wild bee communities exhibit a breadth of functional traits which are related not only to their ability to provide pollination services but may also moderate a community’s response to stressors including land use change.  Here we examine how agricultural simplification of landscapes can negatively impact the health and diversity of pollinator communities and individual pollinator species. We studied pollination services to strawberry, Fragaria x ananassa, in experimental plots across 18 farms varying in landscape structure. We used a novel phylodiversity (PD) approach which describes the total phylogenetic distance among species within a community as a measure of community functional diversity based on bees captured in sweep-net transects at each site. Additionally, we collected fresh weight and morphological measurements of all collected bees. Pollination services were estimated based on a sample of 25 hand-pollinated and 25 open-pollinated fruits from each site. Across farms, PD was strongly correlated with species richness and both were negatively impacted by greater proportions of agriculture in the landscape. However, PD better predicted pollination services to strawberry than species richness. Several of the species collected showed a negative response in body size to landscape simplification. We hypothesize these responses are related to functional traits including sociality and diet breadth.