The Alignment of Natural and Sexual Selection

Sexual selection has the potential to decrease mean fitness in a population through an array of costs to nonsexual fitness. These costs may be offset when sexual selection favors individuals with high nonsexual fitness, causing the alignment of sexual and natural selection. We review the many laboratory experiments that have manipulated mating systems aimed at quantifying the net effects of sexual selection on mean fitness. These must be interpreted in light of population history and the diversity of ways manipulations have altered sexual interactions, sexual conflict, and sexual and natural selection. Theory and data suggest a net benefit is more likely when sexually concordant genetic variation is enhanced and that ecological context can mediate the relative importance of these different effects. Comparative studies have independently examined the consequences of sexual selection for population/species persistence. These provide little indication of a benefit, and interpreting these higher-level responses is challenging.