Evolution of stress resistance in Drosophila: interspecific variation in tolerance to desiccation and starvation

The extent to which variability in desiccation resistance among ecologically diverse Drosophila species is related to their ability to resist starvation is unknown. Resistance to desiccation and starvation was measured in females and males of ecologically and phylogenetically diverse Drosophila species. We measured resistance to both stressors in ecologically and phylogenetically diverse species. In general females exhibited greater resistance to both stressors than males. Correcting for body size produces a highly significant correlation between resistances to both stressors in both sexes. Phylogenetic relatedness, however, appears to have a large influence not only on resistance to both stressors, but also on the observed correlations between stressors. Species of the Drosophila subgenus Sophophora examined in this study tend to be fruit breeders inhabiting more temperate and mesic habitats, whereas many of the species in the other major subgenus, Drosophila, tend to be cactophilic flies living in more xeric environments. The difference between these two major subgenera, the Sophophora and the Drosophila, in the nature of the association we observed between desiccation and starvation resistance suggests that selection may have led to different mechanisms underlying resistance to these stressors in the two groups.