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.