Saccharomyces cerevisiae found in the crop of a Neotropical Drosophila species fly collected in a natural forest remnant – comments on Hoang, Kopp & Chandler (2015)

Abstract Background. Hoang, Kopp & Chandler (2015) questioned the use of commercial Saccharomyces cerevisiae as a model for investigating Drosophila – yeast association, since this approach “may not be fully representative of host-microbe interactions as they operate in nature”. They also claimed: “S. cerevisiae is rarely found with natural populations of D. melanogaster or other Drosophila species”. Indeed, previous choice experiments found that Sophophora subgenus flies (including invasive species D. melanogaster) are more attracted to banana baits inoculated with apiculate yeasts such as Hanseniaspora uvarum over S. cerevisiae inoculated baits. Yet, the forest interior dwelling species (FIDS) D. tripunctata group flies choose preferentially S. cerevisiae inoculated baits over H. uvarum in a natural forest environment. Aim and Methods. Our objective was to carry out a pilot experiment to examine yeast species associated with Drosophila in a natural Atlantic Rainforest fragment, especially examining, the yeast found with FIDS of the D. tripunctata group. We sampled Drosophila in a natural population from a Neotropical forest fragment. Males were dissected for isolating yeast colonies from their crops and to use their genitalia for species identification. Yeast species were identified by sequencing the D1/D2 domains of the 26S rRNA gene. Results and Conclusion. We isolated five yeast species from crops of Drosophila species of tripunctata group, including one strain of S. cerevisiae (from D. paraguayensis), confirming a previous record of S. cerevisiae isolates from a few tripunctata group species. Thus, their contention that “the results from D. melanogaster–S. cerevisiae laboratory experiments may not be fully representative of host–microbe interactions in nature” is probably right, but because D. melanogaster is an invasive species that is preferentially attracted in forests to apiculate yeasts, yet S. cerevisiae may be associated with FIDS Drosophila such as D. paraguayensis.