CHANGES IN THE HERITABILITY OF FIVE MORPHOLOGICAL TRAITS UNDER COMBINED ENVIRONMENTAL STRESSES IN DROSOPHILA MELANOGASTER.

Heritabilities and evolvabilities for morphological traits were compared between two environments in Drosophila melanogaster using parent-offspring comparisons. One of the environments was favorable. The other stressful environment involved a combination of repeated cold shocks, poor nutrition, and ethanol added to the medium, which markedly decreased viability. For wing traits, heritabilities were relatively lower in the stressful environment, while heritabilities for bristle traits were not influenced by conditions. Heritability changes were largely due to an increase in the environmental variance under stress, whereas levels of additive genetic variance were relatively constant. Evolvabilities were similar between environments except for crossvein length.