Microbes, molecules, and mason bees: Pollen provision profiles across a landscape gradient

Wild bees typically forage at a local scale, collecting not only pollen from the surrounding plant communities, but also locally occurring pesticides and microbes. These components become incorporated into the pollen provision and can strongly impact bee development and health. While many studies have explored how pollen diversity varies across landscapes, fewer have examined how other elements of the pollen provision, such as pesticides and microbial communities, are shaped by local land use. To investigate how landscape context affects the pollen provision of the solitary generalist mason bee Osmia cornifrons, we sampled nests across three landscape types in central New York; urban areas, forested sites, and apple orchards. Pollen provisions were screened for pesticide residue and sequenced to characterize their bacterial and fungal communities. We found pesticide concentration and toxicity levels varied significantly by land use type. Microbial communities also differed across landscapes, with forest sites having a higher abundance of lactobacilli. Furthermore, the composition of the bacterial community was significantly correlated with the composition of pesticides present, suggesting a potential causal relationship.