Playing to the crowd: Using Drosophila to dissect mechanisms underlying plastic male strategies in sperm competition games

Post-copulatory sexual selection, the post-mating competition between ejaculates, is now widely established as a potent evolutionary driver. However, the competitive environment males face is also not static, potentially altering the fitness outcomes of current vs future matings. Males of many species use cues of their social environment to adjustment their subsequent mating behaviors and ejaculate economics in the face of fluctuating competition. Here we focus on work in Drosophila fruit flies to assess the current understanding of how and why males make these responses. We discuss the progress on understanding the physiological and molecular mechanisms that translate social information into sophisticated plastic responses. We suggest that the potential fitness benefits of flexible reproductive strategies might generate strong selection on cognitive ability as well as on ejaculate investment. We identify avenues for future research and illustrate how studies on Drosophila can serve as a useful model for understanding behavioral plasticity generally.