Do nutritional profiles of floral pollen correlate with solitary bee microbiomes?

Bee performance and well-being strongly depend on access to sufficient and appropriate resources, in particular pollen and nectar of flowers, which constitute the major basis of bee nutrition. Here, pollen-derived microbes appear to play an important but still little explored role in the plant pollen - bee interaction dynamics, e.g. through affecting quantities and ratios of important nutrients. To better understand how microbes in pollen collected by bees may affect larval health through nutrition, we investigated correlations between the floral, microbial and nutritional composition of larval provisions and the gut microbiota of the solitary megachilid bee Osmia bicornis. Our study reveals correlations between the floral taxonomic composition and nutritional quality of pollen provisions with the complete bacterial community and individual members of both pollen provisions and bee guts. In particular pollen fatty acid profiles appear to interact with specific members of the microbial community, indicating that pollen-derived microbes may play an important role in fatty acid provisioning. Increasing evidence suggests a strong effect of dietary fatty acids on bee performance. Consequently, the correlations between specific fatty acids and the microbial community in O. bicornis larval provisions revealed by our study provide interesting new implications for bee health.