The Effect of an Extreme Environment on Genetic and Phenotypic Variability in Experimental Populations of Drosophila Melanogaster (Meig.)

SUMMARY An experiment was performed with the aim to gather further informations on the role of genetic variability of a quantitative character (wing length) on the dynamics of a population in an extreme environment. Three lines with different heterozygosity levels in respect to parental strains (M and F) obtained after artificial selection for wing length were kept for 30 generations in an extreme environment at a constant temperature of 28°C, and then transferred to an optimal environment at 25°C. In spite of the noticeable inter-populational phenotypic uniformity we found in the mean values, genetic variability seems differentially assigned to the three populations in both environments. The results were discussed on the basis of present hypothesis on the dynamics of a population in an extreme environment, and it was suggested that adaptability in an extreme environment may be the result of selective forces acting on the developmental pattern of an organism rather than on the genetic variability of a sin...