Individual dietary specialization in a generalist bee varies across populations but has no effect on the richness of associated microbial communities

Despite the increasingly documented occurrence of individual specialization, the relationship between individual consumer interactions and diet-related microbial communities in wild populations is still unclear. Using data from nests of the bee Ceratina australensis from three different wild populations, we combine metabarcoding and network approaches to explore the existence of individual variation in resource use within and across populations, and whether dietary specialization affects the richness of pollen-associated microbes. We reveal the existence of marked dietary specialization. In the most specialized population, we also show that individuals' diet breadth was positively related to the richness of fungi, but not bacteria. Overall, individual specialization appeared to have a weak or negligible effect on the microbial richness of nests, suggesting that different mechanisms beyond environmental transmission may be at play regarding microbial acquisition in wild bees.