Effects of stress combinations on the expression of additive genetic variation for fecundity in Drosophila melanogaster.

To test whether stressful conditions altered levels of heritable variation in fecundity in Drosophila melanogaster, parent-offspring comparisons were undertaken across three generations for flies reared in a combined stress (ethanol, cold shock, low nutrition) environment or a control environment. The stressful conditions did not directly influence fecundity but did lead to a reduced fecundity in the offspring generations, perhaps reflecting cross-generation maternal effects. Both the heritability and evolvability estimates were higher in the combined stress treatment, reflecting an apparent increase in the additive genetic variance under stress. In contrast, there were no consistent changes in the environmental variance across environments.