Community assembly of the Hawaiian Drosophila microbiome

Hawaiʻi’s Drosophila, including the iconic picture-wing species, exemplify rapid and dramatic species diversification. Many factors are thought to contribute to this phenomenon, including allopatry, sexual selection, and ecological speciation, but others remain largely untested. In particular, the gut microbiome has been hypothesized to be an important driver of adaptation and phenotypic change for many animals, as it influences host survivorship and detoxification, and enables the colonization of new niches. To determine how microbial communities may contribute to the rapid adaptation of Hawaiian drosophilids, we conducted a survey of bacterial and fungal communities from over 500 wild flies collected from across six islands of the Hawaiian archipelago, including 55 species of native Drosophila, with 30 from the picture-wing clade. These samples represent a breadth of dietary specializations, host plant preferences, habitats, lifestyles, and endemicity. Our findings indicate that gut microbiome community composition is largely driven by abiotic factors including elevation, temperature, rainfall, and evapotranspiration, and is not strongly constrained by phylogenetic relatedness. However, the microbiomes of native species differ from recently introduced, non-native Drosophila, and also from the most prevalent microbes on an important endemic host plant. Given that different gut microbial communities contribute to variation in host phenotypes and that the Hawaiian Drosophila microbiome plays critical roles in reproduction, these results support a role for the gut microbiome in the ecological divergence of these flies.