Culturable bacteria are more common than fungi in floral nectar and are more easily dispersed by thrips, a ubiquitous flower visitor.

Variation in dispersal ability among taxa affects community assembly and biodiversity maintenance within metacommunities. Although fungi and bacteria frequently coexist, their relative dispersal abilities are poorly understood. Nectar-inhabiting microbial communities affect plant reproduction and pollinator behavior, and are excellent models for studying dispersal of bacteria and fungi in a metacommunity framework. Here, we assay dispersal ability of common nectar bacteria and fungi in an insect-based dispersal experiment. We then compare these results with the incidence and abundance of culturable flower-inhabiting bacteria and fungi within naturally occurring flowers across two coflowering communities in California across two flowering seasons. Our microbial dispersal experiment demonstrates that bacteria disperse via thrips among artificial habitat patches more readily than fungi. In the field, incidence and abundance of culturable bacteria and fungi were positively correlated, but bacteria were much more widespread. These patterns suggest shared dispersal routes or habitat requirements among culturable bacteria and fungi, but differences in dispersal or colonization frequency by thrips, common flower visitors. The finding that culturable bacteria are more common among nectar sampled here, in part due to superior thrips-mediated dispersal, may have relevance for microbial life history, community assembly of microbes, and plant-pollinator interactions.