A RESOLUTION OF THE LEK PARADOX

Sexual traits are usually more phenotypically variable than non-sexual traits. We show that additive genetic variation is also higher in sexual traits, and often greater than in the same, non-sexually selected trait in females or other comparable traits in the same species. In contrast there is no difference in residual variation (environmental and non-additive) or heritability. The higher genetic variability of sexual traits is contrary to the expectations of the lek paradox. This hypothesis predicts that strong sexual selection, due to female choice, leads to fixation of most genetic variation in male sexual characters. High genetic variability in sexual traits can be explained if they are subject to directional selection that is greater than linear because this selects for greater phenotypic variation. It favours modifiers that increase the number of genes and the average contribution of a locus to phenotypic variance in sexual traits. These results provide a general resolution of the lek paradox.