The Evolutionary Effects of Mate Selection

Sexual selection is the subset of natural selection that depends on differential success in obtaining mates. Differential mating success within one sex, say males, may depend on the preferences of females for certain males, on the outcome of male-male competition for females, or on some combination of both processes. The purpose of this review is to analyze the evolutionary consequences of that component of sexual selection due to mating preferences. The most important step in such an analysis is to determine which characteristics of one sex determine mating preferences in the other sex, since these characteristics will be favored by sexual selection. In the past there has been much debate over the importance of mate choice as a selection pressure, and, in fact, about whether mate choice occurs at all (32, 63, 82, 128). This controversy can perhaps be largely avoided if mate choice is clearly defined. For the purposes of this review, mate choice includes all instances where there is differential mating success in one sex due to preferences exhibited by the other sex. Under this definition, mate choice includes preferences based on characters conferring genetic benefit to the young, on phenotypic characters conferring a more immediate benefit to the chooser (such as assistance with parental care), or even on characters external to the chosen individual (such as resources it controls).