Evolutionary genetics of Drosophila ananassae: evidence for trade-offs among several fitness traits

Abstract

Correlated responses to bi-directional selection on thorax length, examined on several life-history traits and chromosome inversion polymorphisms, have revealed apparent novel trade-offs in Drosophila ananassae. We provide evidence of trade-offs between hatching time and pupal period, pupal period and egg-pupa development time, and pupal period and larval development time (LDT). Body size shows positive correlations with ovariole number, LDT and DT (egg–fly). We provide evidence of sexual dimorphism for trade-offs between longevity and body size and starvation and longevity in females only. Trade-offs between wing/thorax (W/T) ratio and longevity, W/T ratio and starvation, and DT (egg- fly) and longevity are evident in males only. Sexual dimorphism is also evident for inversion polymorphism with body size and longevity. A longevity assay suggests that low line females outlived high line females whereas high line males outlived low line males. The mean longevity in males is negatively correlated with the 2L-ST and 3R-ST arrangement frequencies whereas the 3L-ST arrangement frequency is positively correlated with the mean longevity in males but opposite arrangements are found in females. Absolute starvation resistance is negatively correlated with 2L-ST and 3R-ST chromosome arrangements and results in a trade-off between longevity and absolute starvation resistance in females. Analyses of fecundity, hatchability, and viabilities based on age intervals in both G10 and G13 suggest that the early reproduction is favoured in D. ananassae. The productivity percentage is highest in the high line and there is no effect of late reproduction on it. Overall, we provide some unravelled trade-offs and striking sex differences, which may help in understanding the life-history evolution of the species. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 90, 669–685.