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 varia tion in fecundity in Drosophila melanogaster, parent-offspring compari sons were undertaken across three generations for flies reared in a co mbined stress (ethanol, cold shock, low nutrition) environment or a co ntrol environment. The stressful conditions did not directly influence fecundity but did lead to a reduced fecundity in the offspring genera tions, perhaps reflecting cross-generation maternal effects. Both the heritability and evolvability estimates were higher in the combined st ress treatment, reflecting an apparent increase in the additive geneti c variance under stress. In contrast, there were no consistent changes in the environmental variance across environments.