Age-specific effects of novel mutations in Drosophila melanogaster - II. Fecundity and male mating ability

Evolutionary theories of senescence assume that mutations with age-specific effects exist, yet until now, there has been little experimental evidence to support this assumption. In this study, we allowed mutations to accumula te in an outbred, wild population of Drosophila melanogaster to test for ag e-specific differences in both male mating ability and fecundity. We assaye d for age-specific effects of mutations after 10, 20, and 30 generations of mutation accumulation. For mating ability, we found the strongest effects of mutations in the first half of the life span after 20 generations, and a t nearly all ages by generation 30. These results are qualitatively consist ent with results from a companion study in which age-specific mortality was assayed on the same lines of D. melanogaster. By contrast, effects of fecu ndity were confined to late ages after 20 generations of mutation accumulat ion, but by generation 30, as with male mating ability, effects of novel mu tations were distributed across all age classes. We discuss several possibl e explanations for the differences that we observe between generations with in traits, and among traits, and the relevance for these patterns to models of aging as well as models of mate choice and sexual selection.