Drosophila Effects on Yeast Communities Figure 6. Effects of virgin adult females and larvae on yeast densities. Larvae either acting alone (b) or with adult females (c) significantly reduced the variance across fruits in yeast densities, as compared to the variance in yeast densities of matched pieces of banana not exposed to flies. doi:10.1371/journal.pone.0042238.g006 C. zemplinina and P. kluvyeri) of the 17 different species collected from the banana fruits used in these experiments benefited from exposure to females and larval processing. At this point, it is not clear why these three yeast species were especially favored in fly-exposed fruits. We do know that all three of these species were able to survive passage through larval guts (see also [34]), and that as a result, these yeasts might be ‘transplanted’ throughout a fruit in the fecal pools of larvae as they crawled around a substrate. The fact that these three species all thrived within larval fecal pools also implies that they were not adversely affected by the presence of uric acid or other larval waste products [10], [35]. Indeed, these species may have been able to use uric acid as a source of nitrogen, as has been reported for other species of yeast (e.g. [36], [37]). In addition, these yeasts might have benefited from the lack of filamentous fungi in fruits processed by larvae, or by the continuous churning of substrates that occurs as a result of larval digging and burrowing behavior [38]. We can also ask a related question, namely how larvae were affected by the yeast community that grew in fly-exposed fruits. At this point, we know that these species of yeast were consumed by larvae, and have indirect evidence that this yeast community was able to support larval growth and survival. We found that strains of Candida californica, C. zemplinina and Pichia kluvyeri collected from bananas exposed to flies were highly palatable to one day old larvae, and that the fecal pools produced by young larvae Figure 7. Yeasts ‘transplanted’ by traveling larvae. Yeast colonies fill the fecal pool deposited by a one day old D. melanogaster larva that had crawled around a RCBA plate 12 h earlier; the larvae also smeared live yeast behind it as it traveled across the plate (direction of travel from right to left). doi:10.1371/journal.pone.0042238.g007 PLoS ONE | www.plosone.org 8 July 2012 | Volume 7 | Issue 7 | e42238