Multivariate selection drives concordant patterns of pre- and postcopulatory sexual selection in a livebearing fish

In many species, females mate with multiple partners, meaning that sexual selection on male traits operates across a spectrum that encompasses the competition for mates (that is, before mating) and fertilizations (after mating). Despite being inextricably linked, pre- and postcopulatory sexual selection are typically studied independently, and we know almost nothing about how sexual selection operates across this divide. Here we bridge this knowledge gap using the livebearing fish Poecilia reticulata . We show that both selective episodes, as well as their covariance, explain a significant component of variance in male reproductive fitness. Moreover, linear and nonlinear selection simultaneously act on pre- and postcopulatory traits, and interact to generate multiple phenotypes with similar fitness. In species in which females mate with multiple partners, sexual selection acts on male traits involved in mating and fertilization. Here, the authors show that selection acting before and after mating explains a significant component of variance in male reproductive fitness in a livebearing fish.