Dispersing species pools reveal how mobile links shape metacommunities of nectar yeasts

Dispersal between local communities is a hallmark of metacommunity theory. Evidence for the effects of dispersal rates and pathways on metacommunity dynamics under field conditions is often lacking. However, studying metacommunities of yeasts in floral nectar and yeasts transported by a mobile linker community offers the opportunity to understand how species pools of passively dispersing organisms affect the community assembly. We sampled flowers and pollinators of three common tree species, identified attached yeast species and observed flower visits of different pollinator groups. We found a high overlap in yeast communities between flower and pollinator for social insects and low overlap for solitary insects. Bumblebees and honeybees transported the most nectar-specialist species, wild bees and wasps the most insect-associated yeast species, and sawflies the most transient yeast species. We found strong environmental filtering for insect-associated yeast species. Our results show that the dispersal frequency of the mobile linker community plays an important role in determining the species richness and the overall species abundance of the metacommunity, whereas local processes like environmental filtering effects mainly shape species composition. This approach offers new insights into the role of ecological filters during dispersal and colonization processes and a better understanding of resulting metacommunities.