Variation in male effects on female fecundity in Drosophila melanogaster.

In many species, males have the capacity to directly influence (either positively or negatively) the fitness of their mates and offspring, not only via parental care contributions and/or precopulatory resource provisioning, but also via the post-copulatory activity of those substances passed on to their mates in their ejaculates. Here, we examine how an individual male's identity may be related to phenotypic variation in short-term female fecundity in the model species, Drosophila melanogaster. The effect of male identity on short-term fecundity stimulation of females was repeatable across time and accounted for over a fifth of the total observed phenotypic variation in fecundity in two independent populations. The functional explanations for these results and the implications for our understanding of the factors that contribute to the adaptive significance of mating preferences and/or sexual conflict are discussed.