microbiomes

Insects carry communities of gut bacteria, and there has been growing interest in whether these microbes shape how their hosts feed, grow, and even choose mates. We investigate these questions in fruit flies (Drosophila and the medfly). One strand of our work critically re-examined the claim that gut bacteria can drive the early stages of speciation: an influential earlier study had reported that flies raised on different diets preferred to mate with their own dietary group, an effect attributed to their gut microbes. When we repeated and extended those experiments, we found no reliable evidence for such mate preference, and argued that because the fly gut microbiome is largely transient and set by whatever the insect has recently eaten, any bacterially mediated reproductive isolation would be short-lived rather than a stable driver of divergence (Leftwich et al., 2017, PNAS, 114:12767–12772). Related work showed that diet, rather than the host itself, is the main force shaping which microbes associate with flies, and that transmission efficiency governs how tightly hosts and microbes become linked (Leftwich et al., 2020, Proceedings of the Royal Society B). This line of research connects to the applied side of our work, since manipulating gut microbes through probiotics is being explored as a way to improve the quality and performance of mass-reared insects used in pest control.