Reproductive Advantages in Sequential Drosophila Pseudoobscura Matings

Abstract

Frequency dependent mating occurs when the proportion of matings among different genotypes (or phenotypes) depends on the proportion of genotypes present in the population. In many, but not all, experimental Drosophila populations, the minority genotype is favored in mating at the expense of the more common genotype (Ehrman and Probber, 1978 for review). This rare male advantage has been reported in eight Drosophila species (D. immigrans, D. melanogaster, D. pseudo-obscura, D. persimilis, D. willistoni, D. tropicalis, D. equinoxialis, and D. funebris) as well as among other insects, such as Tribolium castaneum (Sinnock, 1970) and Mormoniella (Grant et al., 1974). The advantages conferred by being rare may result in an increase in genotype frequency until this frequency dependent advantage disappears. Such a mechanism may help to maintain assorted alleles and genetic polymorphisms in natural populations and therefore be of evolutionary importance. While rare males show an advantage in the laboratory, we know little about the fates of rare males in natural populations (Crumpacker et al., 1977).