Sexual conflict and sperm competition

Traits that increase a male’s fertilization success during sperm competition can be harmful to females and therefore represent a source of sexual conflict. In this review, we consider the variety of male adaptations to sperm competition (MASC) that may give rise to sexual con-flict—including mate guarding, prolonged copulations, the transfer of large numbers of sperm, and the manipulation of females through nonsperm components of the ejaculate. We then reflect on the fitness economics influencing the escalation of these sexual conflicts, considering the likelihood of females evolving traits to offset the negative effects of MASC when compared with the strong selection on males that lead to MASC. We conclude by discussing the potential evolutionary outcomes of sexual conflict arising from MASC, in-cluding the opportunities for females to mitigate conflict costs and the prospects for conflict resolution. Male mate competition can lead to sexualconflict because male traits that increase the chances of securing a mate can reduce fe-male fitness. For example, intense male–male competition for females in yellow dungflie