Variable dependency on associated yeast communities influences host range in Drosophila species

The tight association between yeast metabolites and the attraction of fly species provides key evolutionary innovations that generate immense diversity within the genus Drosophila. Why and how changes in Drosophila niche preferences occur, and what role yeasts play in species specialization, is still largely unknown. Here, we analyze adult preference and larval development across three species of Drosophila as well as niche modifications through joint efforts by both insect and yeast. In general, we found that niche specialization is more a result of larval constraints than adult oviposition choice. We also determined that different life stages of fly development vary in their respective yeast preference, which may reduce cross-generational competition for resources. In this way, natural selection pressures may act quite differently on adult or larval performance, with adaptation events in larval stages likely being the stronger driver of niche evolution. Furthermore, we provide evidence that Drosophila and yeast together process host material to promote mutual benefits. Our data indicate that adult Drosophila flies of different species are flexible in their yeast preference and can be attracted to yeast species from radically different habitats. This argues against stable Drosophila-yeast associations and for broader acceptance of diverse yeast species across adult individuals in the genus Drosophila.