Females aren’t perfect: maintaining genetic variation and the lek paradox

Abstract

The evolution of lek mating systems and female choice for ‘good genes’ has received unparalleled inquiry on both theoretical and empirical fronts in evolutionary ecology over the past decade. On a lek, males typically congregate and display exaggerated sexual traits (for example the elaborate trains of male peacocks) to choosy females, which receive only sperm (genes) from their mate. Females generally prefer males with the most exaggerated trait, presumably because these males have the highest quality genes. Population genetic theory predicts that unanimous female choice for these ‘popular’ males will, however, lead to rapid loss of variation in male genetic quality and, subsequently, females will gain nothing from their choice. This conundrum has been termed the ‘paradox of the lek’. To date, the most convincing resolution of the paradox has assumed that exaggerated sexual traits are controlled by relatively large numbers of loci and, consequently, high mutational input maintains the genetic variation. Empirical evidence shows that sexual traits do, in fact, exhibit greater genetic variation than comparable nonsexual characters. Thus, females are choosing for good genes (or avoiding bad genes) in their mates. An alternative to mutational input, the increased genetic variation in sexual traits could be maintained by weaker selective loss; for example, if females occasionally made mistakes when choosing their mate. However, this simple alternative solution to the lek paradox has received little attention. That is, until now.