PHENOTYPIC PLASTICITY IN MORPHOLOGICAL TRAITS IN 2 POPULATIONS OF DROSOPHILA-MELANOGASTER

Isofemale lines of two populations of Drosophila melanogaster, origina ting from France and Tanzania, were examined over a range of temperatu res. Morphological traits showed distinct patterns in phenotypic plast icity; flies of the two populations differed in shape. Genotype-by-Env ironment (GE) interactions were frequently found in the Tanzania popu lation, but were hardly present in the France population. If GE inter action was present over temperature, estimates of additive genetic var iance and additive genetic covariance were made to compare theoretical models with our data. The conclusion is that in France Drosophila mel anogaster has been selected over a wider range of temperatures, result ing in parallel reaction norms of more optimal slope. In contrast, sel ection must have taken place over a narrower temperature range in Tanz anian flies, and will have exerted no direct influence on the slope of the reaction norm.