Gut microbiomes and reproductive isolation in Drosophila

Abstract

Experimental studies of the evolution of reproductive isolation (RI) in real time are a powerful way in which to reveal fundamental, early processes that initiate divergence. In a classic speciation experiment, populations of were subjected to divergent dietary selection and evolved significant positive assortative mating by diet. More recently, a direct role for the gut microbiome in determining this type of RI in has been proposed. Manipulation of the diet, and hence the gut microbiome, was reported to result in immediate assortative mating by diet, which could be eliminated by reducing gut microbes using antibiotics and recreated by adding back We suggest that the evolutionary significance of this result is unclear. For example, in, the microbiome is reported as flexible and largely environmentally determined. Therefore, microbiome-mediated RI would be transient and would break down under dietary variation. In the absence of evolutionary coassociation or recurrent exposure between host and microbiome, there are 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 Despite observing replicable differences in the gut microbiomes of flies maintained on different diets, we found no evidence for diet-associated RI, for any role of gut bacteria, or for specifically. The results suggest that there is no general role for gut bacteria in driving the evolution of RI in this species and resolve an evolutionary riddle.

The Drosophila microbiome has a limited influence on sleep, activity, and courtship behaviors

“…This outcome contrasts with earlier reports demonstrating a major role for the microbiota in fly mate choice 35,36 . The current observations are in line with recent work finding that diet-induced microbial changes did not alter mate choice 37 .…”

“…In these studies, dietary shifts were used to perturb microbiota compositions over multiple generations. In contrast, a recent report failed to detect a role for the Drosophila microbiota in mating preferences after dietary shifts and antibiotic exposure 37 . To test whether direct microbe removal impacts microbiota-dependent attractiveness, conventional male flies were placed in a chamber together with decapitated GF and CV female bodies, and their courtship was monitored for 60 minutes (Figure 6 A).…”

Diet, Gut Microbes and Host Mate Choice

“…A remarkable and puzzling observation was that the effect of diet on assortative mating, and its prevention by antibiotic treatment, was effectively instantaneous, indicating a direct effect of the presence of the bacteria. However, other studies showed that neither the significant positive assortative mating by diet, nor the involvement of gut bacteria in this process, is consistent within or across different Drosophila strains either instantaneously or across generations …”

“…The development of sequencing technologies has enabled rich descriptions of the communities of non‐culturable as well as culturable bacteria that are found on or in different hosts and in novel ecological niches . One increasing area of interest has been the relationships between hosts and their commensal gut microbes …”

Diet‐based assortative mating through sexual imprinting

“…In Drosophila, assortative mating preferences by diet have been proposed to result from correlated dietary traits. Specifically, it was suggested that feeding flies of the same strain different diets significantly altered their gut microbiota, changing pheromone mating signals as a result (Rosenberg, Zilber-Rosenberg, Sharon, & Segal, 2018;Sharon et al, 2010), although subsequent studies failed to replicate resulting patterns of diet-based assortative mating (Leftwich et al, 2017). Furthermore, when diet-based assortative mating has been detected so far, it has been limited to inbred, not outbred, Drosophila strains (Najarro, Sumethasorn, Lamoureux, & Turner, 2015).…”