Variation in Male Mating Success on Leks

Abstract

Studies of variation in male mating success within populations have been instrumental in shaping perspectives of the role of female choice in sexual selection. We present simple models to quantify the potential contributions to such variation from a variety of processes: average male mating success (equivalent to the number of female matings per male), variation in male and territory quality, male attendance times at leks, and degree of female synchrony, aggregation, and copying. If matings occur by chance, we expect variance in male mating success to increase proportionately with mean mating success. Increasing average mating success results in a superproportionate increase in variance when males or their territories differ in quality, when males differ in time spent at the lek, when females copy each other, or when females aggregate and mate as a group. In contrast, when females arrive in synchrony there is a subproportionate increase in variance with respect to mean male mating success. A review of 36 field studies from 20 species indicates that all studied leks exhibit greater variance in male mating success than expected by chance. Furthermore, the slope of a regression between variance and mean success is significantly greater than unity, as predicted by the models of variation in male quality, attendance at leks, female aggregation, and female copying. In studies of four leks in which we were able to partition the component of variance attributable to differences among males in attendance at leks, approximately 60% of the variance remained unexplained and was attributable to female copying, aggregation, or variation in male quality. The framework presented here allows a quantified breakdown of variation among males in mating success and facilitates comparisons among studies of the potential for sexual selection.