Using potential reproductive rates to predict mating competition among individuals qualified to mate

The potential reproductive rate (PRR), which is the offspring production pe r unit time each sex would achieve if unconstrained by mate availability, o ften differs between the sexes. An increasing sexual difference in PRR pred icts an intensified mating competition among the sex with the higher PRR. T he use of PRR can provide detailed predictions of when, where, and how the intensity in mating competition and hence sexual selection will vary. Previ ous models have focused on the "time out" from mate searching as a major co mponent of PRR. Here, we suggest some improvements and clarifications: in a population where individuals have to compete for specific resources that a re prerequisites for mating (e.g., nest sites), individuals unable to obtai n such a resource will not qualify to mate. We suggest how a concept of the ratio of males and females qualified to mate, Q can improve previous model s designed to use the sexual difference in PRR to estimate the operational sex ratio (OSR). Further, when estimating the sexual difference in PRR of a population, it is important that each sex is given free access to mating p artners. Jointly, this provides an empirical approach based on estimates of Q and the sexual difference in PRR.