Genotype-temperature interaction in Drosophila melanogaster. II. Body weight.

The effect of genotype-temperature interactions on body weight has been studied in a natural population of Drosophila melanogaster using four isogenic strains derived from it, and their hybrid F(1) and F(2) progenies. Measurements were made at four constant temperatures-25 degrees , 21 degrees , 17 degrees and 13 degrees C-and at a temperature oscillating between 17 degrees and 25 degrees C.-Low, though significant, genotype-temperature interaction exists among the isogenic strains, but not among the F(1) nor F(2) hybrid progenies. These low interaction values may be due to the fact that all isogenic strains have a common origin and therefore presumably little genic divergence exists among them. F(1) and F(2) hybrid progenies generally exhibit higher homeostasis than the isogenic strains, although one isogenic line has better homeostasis than the majority of the hybrids.-There is no evidence of heterosis and some evidence of dominance. These results are consistent with the hypothesis that body weight is regulated mainly by additive genetic factors and is subject to stabilizing selection.