Host determinants of among-species variation in microbiome composition in drosophilid flies.

The taxonomic composition of microbial communities in animals varies among animal species, but the contribution of interspecific differences in filtering of the microbial pool by the animal host to this variation is uncertain. Here, we demonstrate significant interspecific variation in microbial community composition among laboratory-reared Drosophila species that was not related to host phylogeny. Complementary reciprocal transfer experiments yielded different microbial communities for a single microbiota administered to homologous and heterologous hosts (i.e., the same and different Drosophila species from which the microbiota was derived), indicative of among-host species differences in traits that shape microbiota composition. The difference in microbiota composition between homologous and heterologous hosts was not greater for distantly related than for closely related host species pairs. Furthermore, Drosophila survival to adulthood was significantly reduced in heterologous associations relative to homologous associations and microbiologically sterile flies, suggesting that microbial taxa that are advantageous for their homologous host species can be deleterious for other host species. We conclude that drosophilid flies display robust among-host species variation in host controls over microbiota composition that has diversified in response to selection pressures which are not tracked by host phylogeny.