A model of sexual selection and female use of refuge in a coercive mating system

Abstract

In many non-monogamous systems, males invest less in progeny than do females. This leaves males with higher potential rates of reproduction, and a likelihood of sexual conflict, including, in some systems, coercive matings. If coercive matings are costly, the best female strategy may be to avoid male interaction. We present a model that demonstrates female movement in response to male harassment as a mechanism to lower the costs associated with male coercion, and the effect that female movement has on selection in males for male harassment. We found that, when females can move from a habitat patch to a refuge to which males do not have access, there may be a selection for either high, or low harassment male phenotype, or both, depending on the relationship between the harassment level of male types in the population and a threshold level of male harassment. This threshold harassment level depends on the relative number of males and females in the population, and the relative resource values of the habitat; the threshold increases as the sex ratio favours females, and decreases with the value of the refuge patch or total population. Our model predicts that selection will favour the harassment level that lies closest to this threshold level of harassment, and differing harassment levels will coexist within the population only if they lie on the opposite sides of the threshold harassment. Our model is consistent with empirical results suggesting that an intermediate harassment level provides maximum reproductive fitness to males when females are mobile.

On the evolutionary stability of male harassment in a coercive mating game

“…In summary, we showed that the Bokides et al [1] model only exhibits equilibrium behavior. We also proved that any existing equilibrium strategy would be globally asymptotically stable, improving on their results.…”

“…For the reader's convenience, we briefly review and summarize main results of the Bokides et al model [1]. The model is styled similar to classical habitat choice games [13] with a fixed population of females (N f ) and males (N m ) vying to maximize resource intake and mating benefits.…”

“…Table 1). Bokides et al [1] showed that the interior equilibrium where males use a probabilistic mix of low and high harassment (i.e., h r and h i ) with females present was stable if and only if there existed intermediate harassment threshold:…”

“…In section 2, we briefly summarize the mating game model presented in Bokides et al [1]. In section 3, we present our main results.…”

“…Inspired by the mating conflict in A. remigis and similar systems [9,10], Bokides et al [1] modeled the dynamics of female patch use and male harassment as a habitat choice game with predator-prey style interactions. Their analysis revealed that selection always favored male strategies with harassment closest to a threshold level h * .…”