Differential attraction of drosophilids to banana baits inoculated with and within a Neotropical forest remnant.

Background: Yeasts are a necessary requisite in the diet of most species that, in turn, may vector their dispersal in natural environments. Differential attractiveness experiments and the isolation of yeasts consumed by may be informative for characterizing this association. is among the most common yeast species isolated from crops, with high attractiveness to drosophilids. has been widely used to collect flies, and it allows broad sampling of almost all local species. Pronounced differences in the field concerning attractivity to baits seeded with these yeast species have been previously reported. However, few explicit generalizations have been set. Since late fifties, no field experiments of attractivity were carried out in the Neotropical region, which is facing shifts in abiotic and biotic factors. Our objective is to characterize preference behavior that mediates the interaction in the wild among Neotropical species and yeasts associated with them. We want to set a broad generalization about drosophilids attracted to these yeasts. Here we present the results of a differential attractiveness experiment we carried out in a natural Atlantic Rainforest fragment to assess the preferences of species groups to baits inoculated with and .

Methods: Both yeast species were cultured in GYMP broth and separately poured in autoclaved mashed banana that was left fermenting. In the field, we collected drosophilids over five arrays of three different baits: non-inoculated autoclaved banana and banana inoculated with each yeast. In the laboratory the drosophilids were sorted to five sets according to their external morphology and/or genitalia: ; ; ; ; and the remaining flies pooled in .

Results And Conclusions: Uninoculated banana baits attracted virtually no flies. We found significant departures from random distribution over the other two baits (1:1 proportion) for all sets, except the pooled . Flies of the sets and preferred . over . while the remaining sets were more attracted to . . Previously, various authors reported similar patterns in attraction experiments with . and . . It is also noteworthy that both yeast species have been isolated from natural substrates and crops of species. Taken together, these results suggest that the preferences among species groups may be reflecting deep and stable relations with yeast species in natural environments. They can be summarized as: forest dwelling species from subgenus (such as and groups) are attracted to banana baits seeded with . ; while exotic (as ) and subgenus species are preferentially attracted to baits seeded with . .