The effects of larval density on adult life-history traits in three species of Drosophila

There is evidence that longevity and starvation resistance are determined by a common genetic mechanism. Starvation resistance in Drosophila strongly correlates with both fat content and longevity, and is affected by density during rearing. In this study, we examine how three species, Drosophila melanogaster, Drosophila ananassae and Drosophila willistoni, respond to three larval density treatments. Starvation resistance after adult eclosion, and after 2 days of feeding, and longevity were examined in each sex. D. willistoni reacted differently to larval density than the other two species. This species showed an effect of density on longevity whilst D. ananassae and D. melanogaster showed no such effects. The results also indicate that starvation resistance is not solely determined by fat content. Resistance to starvation at two time points after eclosion differed among species. This may reflect differences in resource acquisition and allocation, and we discuss our findings in relation to how selection may operate in the different species.