Genetic polymorphism and high detrimental load in natural populations of Drosophila melanogaster from cellar and vineyard

Abstract

Two Spanish natural populations of Drosophila melanogaster have been analysed with respect to genetic variability in third chromosome viability. The two populations, although from the same locality, belong to relatively different habitats: the inside of a cellar and a vineyard. The patterns of homozygote and heterozygote viability are similar in both populations. The homozygous detrimental loads estimated are very high and the values for the D:L (detrimental/lethal) ratio close to 2.5, which is higher than any previously found. The environmental variance of viability, average degrees of dominance of lethal genes and of viability polygenes and effective population sizes were estimated in each population. The mechanisms which could maintain variability in these populations, the causes of the high detrimental loads and the possibility that cellar and vineyard could be two subpopulations of a larger population are discussed.