Mating competition in artificial populations of Drosophila melanogaster polymorphic for ebony

Abstract

Two aspects of sexual selection which may be important in maintaining the polymorphism for the ebony gene in artificial Drosophila melanogaster populations were investigated. The number of females a single male can inseminate in a 24 h period was found to be light-dependent as well as dependent upon the genotype of both the males and females. In light the mating capacity of ebony males is 50% higher than that of +/+ males, but 30% lower than that of el+ males; in darkness the mating capacity of ele males is 70% higher than for +/+ males and 30% higher than for el+ males. All male types inseminate fewer wild type females than ele and el+ females in both light and darkness. Population cage mating experiments in which ele,+1/+ and el+ flies are mated for 24 h of light or darkness under conditions of strong male competition showed that in light the mating frequencies (average no. of females inseminated) of el+, ele and +/+ males are 0.38, 0.18, 0.19, respectively, In darkness the mating frequencies of el+, ele and +/+ males are 0.31, 0.30 and 0.21, respectively, the light vs. dark differences of el+ and ele males being highly significant. In light all males show a preference for el+ females, but in darkness no preference with respect to female genotype is shown by any type of male.