Relative male age, fertility, and competitive mating success in Drosophila melanogaster.

Female choice experiments were used to investigate the effect of relative male age on mating success in D. melanogaster. Experiments were conducted with a Canton-S (CS) strain, in which two virgin males of different ages (2, 4, or 8 days old) were offered to virgin females. Older males were found to be more successful under competitive conditions in another group of experiments, vermilion (v) males of different ages competed with CS males of different ages. The competitive success of v males was found to increase with their relative age. Male fertility at 2, 4, and 8 days of age was documented for both male genotypes mated with CS females. CS males fathered more offspring per copulation than v males, and the fertility of all males was found to increase with age. Discussion focuses on the changes in male mating success and fertility with age and genotype.