Life Cycle and the Expression of Heterosis in Inversion Heterozygotes in Drosophila funebris and Drosophila pavani

Abstract

In 3 stocks of P. funebris, and in 2 stocks of P. pavani. there is a higher frequency of inversion heterozygotes among adult flies than among larvae. Nevertheless, there exist some differences according to the species, the stock, or the chromosome considered. In P. funebris, 100-day-old flies contain a greater frequency of heterozygotes than young (10-day-old) flies. In P. pavani, the incidence of 2d chromosome inversion heterozygotes is about the same in young and in old flies, but is significantly higher in these than in larvae. In this same species, the frequency of 4th chromosome inversion heterozygotes is about the same in larvae and in young adults, but, at least in one stock, it is significantly higher in 100-day-old flies. The general conclusion is that there is differential mortality favoring the inversion heterozygotes. The selective pressures which confer a higher fitness to these heterozygotes seem to act both at the preadult and adult stages of life.