Age-related decrease in male reproductive success and song quality in Drosophila montana

Abstract

In the present paper, we have studied the effects of aging on male reproductive success and song quality in Drosophila montana. We analyzed the reproductive success of wild-caught males at their normal breeding age during the mating season and after maintaining the males in laboratory from 1 to 5 months. In line with the mutation accumulation theory of aging, none of the factors affecting the reproductive success of wild-caught males during the mating season were related to male longevity. However, mating activity and progeny production of the males decreased with male age. Interestingly, there was no significant variation in progeny production between males at their normal breeding age, whereas at older age, the variation between males becomes significant. The quality of sexually selected song traits deteriorated with male age in concert with the decrease in male reproductive success. The size of the males did not have an effect on male reproductive success at the normal breeding age, but at older age, larger males were able to maintain the sexually selected carrier frequency of the song at higher level than the smaller males. We conclude that by experimentally extending the reproductive age of the males beyond that which they normally experience in nature, it is possible to expose relationships between reproductive success, sexually selected characters, and body size that are not apparent when analyzed for the males at their normal breeding age.