The Best Mate

Abstract

Males and females have differing strategies when it comes to maximizing their fitness. In general, males are limited by the availability of receptive females, while females are constrained by the number of offspring they can produce. However, their availability for reproduction largely determines which sex competes and which is most selective about their breeding partner. Typically, the sex that requires more time to go through one reproductive cycle (thus being unavailable for breeding) is the sex that invests more in reproduction; correspondingly, they tend to be choosiest. Alternatively, the sex available to breed for more time typically invests less in offspring and competes for members of the opposite sex. Thus, while males usually compete for choosy females, the opposite may be true, or both sexes may be choosy. When competing, indirect means (e.g. finding mates, sexual endurance) and direct interactions (fighting) may result in selection for different characteristics. ‘Intrasexual selection’, often used interchangeably with ‘female choice’, has been used to explain the evolution of elaborate male traits. Runaway selection, the handicap principle, parasite resistance, and mitonuclear compatibility have all been proposed as hypotheses for intrasexual selection. Current evidence suggests choosing high-quality mates may be based on parasite resistance or overall energy levels.