Adult male nutrition and reproductive success in Drosophila melanogaster.

Explanations for the maintenance of variation in reproductive traits influenced by seminal fluid accessory gland proteins (Acps) in male Drosophila melanogaster include nontransitivity in the outcome of sperm competition and/or condition dependence of the traits involved. We investigated the effects of adult male nutrition (five diets) on the expression of Acp- and sperm- mediated traits. We found novel, nonlinear effects, with females showing lower levels of refractoriness to remating after mating with males held on the lowest and highest yeast diets. There were no significant effects of adult male nutrition on male paternity share, but there was a striking, nonlinear effect on second male progeny production, with males kept on intermediate yeast diets fathering the highest number of offspring. Such "bell shaped" responses of life-history traits to nutrition have only previously been reported for longevity. Consistent with previous reports, males maintained on low protein diets had lower premating success and gained fewer rematings with nonvirgins. We show novel and body size independent effects of adult male nutrition on traits influenced by Acps and sperm, which do not fit current condition-dependent handicap models and can affect the strength of sexual selection acting upon such fitness-related traits.