Male reproductive phenotypes can evolve in response to the social and sexual environment. The expression of many such phenotypes may also be plastic within an individual’s lifetime. For example, male Drosophila melanogaster show significantly extended mating duration following a period of exposure to conspecific male rivals. The costs and benefits of reproductive investment, and plasticity itself, can be shaped by the prevailing socio-sexual environment and by resource availability. We investigated these ideas using experimental evolution lines of D. melanogaster evolving under three fixed sex ratios (high, medium and low male-male competition) on either rich or poor adult diets. We found that males evolving in high-competition environments evolved longer mating durations overall. In addition, these males expressed a novel type of plastic behavioural response following exposure to rival males: they both significantly reduced and showed altered courtship delivery and exhibited significantly longer mating latencies. Plasticity in male mating duration in response to rivals was maintained in all of the lines, suggesting that the costs of plasticity were minimal. None of the evolutionary responses tested were consistently affected by dietary resource regimes. Collectively, the results show that fixed behavioural changes and new augmentations to the repertoire of reproductive behaviours can evolve rapidly.

Data collected as describe in read me tabs on excel file.

Readme files incorporated next to raw data tabs.