Gut microbiomes and reproductive isolation in Drosophila.

In Drosophilids, the microbiome is reported as flexible and largely environmentally-determined. Therefore, RI would be transient and break down under dietary variation. In the absence of co-association between host and microbiome, there are also no advantages for the gut bacteria or host in effecting RI. To explore these puzzling effects and their mechanisms further, we repeated the tests for RI associated with diet-specific gut microbiomes in D. melanogaster found in Sharon et al 2011. Despite observing differences in the gut microbiomes in flies maintained on different diets, we found no evidence for diet-associated RI or for any role of gut bacteria, or for L. plantarum specifically. The results suggest that there is no general role for gut bacteria in driving the evolution of RI in this species and hence resolve this evolutionary riddle.