How males can gain by harming their mates: Sexual conflict, seminal toxins, and the cost of mating

We suggest that damaging mating tactics, such as physical aggression, the e volution of genital barbs and spines, and the transfer of seminal toxins ma y serve as a general means by which males can induce females to avoid or to delay remating. Provided that cumulative damage has an accelerating impact on fitness, a female who has already been harmed by previous partner(s) ma y do best to refrain from remating to avoid suffering still further damage. Consequently, a male can gain through the imposition of mating costs, even though this may reduce female fitness because by doing so he minimizes the chances that his mate will copulate again. We develop a game theoretical m odel of this possibility, focusing on toxin transfer as an illustrative exa mple. We show that toxicity as a means of inhibiting remating is phenotypic ally stable over a broad range of conditions (although, under some circumst ances, it may be necessary to invoke other selective pressures to account f or the initial evolution of toxicity). The model predicts that toxin transf er should be more common (and involve greater levels of toxicity) in specie s with greater last-male mating advantage; it is also most likely where the poison inflicts strongly accelerating, dose-dependent costs on females.