Loyal evolutionary partners, or just acquaintances from the same neighborhood?

Submitted by editor on 29 April 2020.Get the paper!

Fig. 1. Female Drosophila melanogaster sitting on one of its preferred fruit, a banana.

"Variable dependency on associated yeast communities influences host range in Drosophila species" (Koerte et al. 2020)

In the study “Variable dependency on associated yeast communities influences host range in Drosophila species”, my colleagues and I wanted to find out whether vinegar flies prefer yeasts that they encounter in their native habitats over yeasts from different environments, where a natural encounter is very unlikely. Would our flies be loyal to the yeasts that provide them with food and other advantages or would the flies be attracted to new types of yeasts, one that could impact their performance in an unforeseeable manner? We conducted our experiments with three different fly species, that normally either feed on yeast growing on fruit (Drosophila melanogaster, Fig. 1), cacti (Drosophila mojavensis, Fig. 2), or mushrooms (Drosophila putrida, Fig.3). Surprisingly, adults of our tested vinegar fly species did not necessarily prefer yeasts from a shared neighborhood but the insects were also attracted to yeasts from drastically different habitats. Even more interestingly, females of some fly species chose to lay their eggs in presence of yeasts that would negatively affect the development of their offspring or actually kill them. Seemingly, mother does not always know best, at least in vinegar flies! For the larvae of vinegar flies with a specialized lifestyle, we observed that overall they would thrive with yeasts from a shared habitat and perform significantly worse with yeasts from unfamiliar environments. In contrast, larvae of vinegar flies with a more flexible lifestyle showed a higher tolerance throughout their development for a variety of yeasts. From these results we concluded that the acceptance of different vinegar fly species for diverse microbes in food sources at different stages of their lives is reflected in the range of habitats that the flies can be found in. We speculate that if the offspring of vinegar flies can survive the association with yeasts from an unfamiliar habitat, this holds the potential for adaptation processes towards new environments, which ultimately could lead to speciation events in vinegar fly species.

Fig. 2. Female Drosophila mojavensis sitting on its preferred plant, a cactus.

Fig. 3 Female Drosophila putrida sitting on its preferred host, a mushroom.

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