Evidence for selection by male mating success in natural populations of Drosophila pseudoobscura.

Abstract

Gene arrangement frequencies were determined at 2 stages in the life history of D. pseudoobscura taken from nature. Three populations in the central highlands of Mexico were each sampled twice during 1976. Gene arrangement frequencies were measured in adult males and in larvae that were the offspring of females collected at the same time. The adult males were a representative sample of those who fathered the larvae produced by the wild females. Differences in gene arrangement frequency between these 2 life stages should indicate the operation of natural selection. One-third of the comparisons of common gene arrangement frequencies in males and in larvae from the next generation were statistically significant, as were 1/3 of the comparisons of total frequency arrays in the 2 life stages. The components of selection that could produce such frequency changes were considered and male mating success must be the major one. Gene arrangement frequencies in the Mexican populations fluctuate within wide bounds. Selection must act to retain the polymorphism in the face of this flux in gene arrangement frequencies, and male mating success probably plays an important role.