The relative importance of host phylogeny and dietary convergence in shaping the bacterial communities hosted by several Sonoran Desert <i>Drosophila</i> species

Complex eukaryotes vary greatly in the mode and extent that their evolutionary histories have been shaped by the microbial communities that they host. A general understanding of the evolutionary consequences of host-microbe symbioses requires that we understand the relative importance of host phylogenetic divergence and other ecological processes in shaping variation in host-associated microbial communities. To contribute to this understanding, we described the bacterial communities hosted by several Drosophila species native to the Sonoran Desert of North America. Our sampling consisted of four species that span multiple dietary shifts to cactophily, as well as the dietary generalist D. melanogaster, allowing us to partition the influences of host phylogeny and extant ecology. We found that bacterial communities were compositionally indistinguishable when considering incidence only but varied when considering the relative abundances of bacterial taxa. Variation in community composition was not explained by host phylogenetic divergence but could be partially explained by dietary variation. In support of the important role of diet as a source of ecological selection, we found that specialist cactophilic Drosophila deviated more from neutral predictions than dietary generalists. Overall, our findings provide insight into the evolutionary and ecological factors that shape host-associated microbial communities in a natural context.