The microbiota of influences the larval development of .

Microorganisms play a central role in the biology of vinegar flies such as and : serving as a food source to both adults and larvae, and influencing a range of traits including nutrition, behavior, and development. The niches utilized by the fly species partially overlap, as do the microbiota that sustain them, and interactions among these players may drive the development of crop diseases. To learn more about how the microbiota of one species may affect the other, we isolated and identified microbes from field-caught , and then characterized their effects on larval development time in the laboratory. We found that the microbiota consistently included both yeasts and bacteria. It was dominated by yeasts of the genus , and bacteria from the families Acetobacteraceae and Enterobacteriaceae. Raising under gnotobiotic conditions with each microbial isolate individually, we found that some bacteria promoted larval development relative to axenic conditions, but most did not have a significant effect. In contrast, nearly all the yeasts tested significantly accelerated larval development. The one exception was , which had the opposite effect: significantly slowing larval developmental rate. We investigated the basis for this effect by examining whether cells could sustain larval growth, and measuring the survival of and other yeasts in the larval gut. Our results suggest is not digested by and therefore cannot serve as a source of nutrition. These findings have interesting implications for possible interactions between the two species and their microbiota in nature. Overall, we found that microbes isolated from promote larval development, which is consistent with the model that infestation of fruit by can open up habitat for . We propose that the microbiome is an important dimension of the ecological interactions between species.