Stress and metabolic regulation in Drosophila.

Environmental changes that result in stress (defined here as decreased absolute viability and/or fecundity) result in extrinsic changes in metabolism that are to some extent compensated by altered gene expression. The fact that different genotypes may respond differently to environmental stress may be of key importance to the maintenance of genetic variation in metabolic traits. Here we quantify a set of metabolic characters in genetically defined lines of Drosophila melanogaster subjected to four stresses (3% acetic acid, 3% ethanol, starvation and thermal stress) in order to assess the magnitude of environmental effects and genotype x environment interactions. Genetic correlations were quantified, and many exhibit significant heterogeneity across environments. Pleiotropically related traits may exhibit the phenomenon of apparent selection, whose effects may be particularly strong in stressful environments. This transient apparent selection may have a large consequence on the maintenance of genetic variation.