Divergence and Convergence of the Gut Microbiomes of Wild Insect Pollinators

Background: Pollination services provided by wild insect pollinators are critical to natural ecosystems and the economic value of crops around the world. Gut microbiota of these insects may determine health and the contributions of their hosts to these services. Thus, phylogenetically divergent insect pollinators represent a crucial system in which to investigate evidence for factors contributing to the assembly of host microbial communities, which is a general question in host-microbiota research. We investigated the microbiomes of multiple insect pollinator species from China, distributed across three insect orders. Results: We found lineage-specific divergences of dominant microbial genera and microbiota community compositions across the divergent insect pollinator genera. However, we found no broad phylogenetic signal underlying these divergences, even though one is present at finer phylogenetic scales. Although there is clearly no single insect pollinator associated gut microbiota, there is suggestive evidence that ecology, including diet, may be associated with community structure. Indeed, we uncover a similar microbe in the gut microbiomes of a pollinator fly and bees, but comparative genomics indicates potential functional differences that could relate to the evolution with host or other microbiota members. Conclusions: Overall, this study suggests selective processes involving ecology or physiology, or neutral processes determining microbe colonization may predominate in the turnover of lineages in insect pollinators broadly, while evolution with hosts and co-occurring microbes may occur under certain circumstances and on smaller phylogenetic scales.