Plastic male mating behavior evolves in response to the competitive environment

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, maleDrosophila melanogastershow 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 sociosexual environment and by resource availability. We investigated these ideas using experimental evolution lines ofD. melanogasterevolving 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 behavioral 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 behavioral changes and new augmentations to the repertoire of reproductive behaviors can evolve rapidly.

Automated summary

Male reproductive phenotypes can evolve in response to the social and sexual environment, with factors such as plasticity and resource availability shaping the costs and benefits of reproductive investment. Experimental evolution lines of D. melanogaster showed that males evolving in high-competition environments developed longer mating durations and exhibited a novel plastic behavioral response following exposure to rival males. The results suggest that fixed behavioral changes and new augmentations to the repertoire of reproductive behaviors can evolve rapidly, with minimal costs of plasticity.