Paternity analysis reveals sexual selection on cognitive performance in mosquitofish

In many animal species, cognitive abilities are under strong natural selection because decisions about foraging, habitat choice and predator avoidance affect fecundity and survival. But how has sexual selection, which is usually stronger on males than females, shaped the evolution of cognitive abilities that influence success when competing for mates or fertilizations? We aimed to investigate potential links between individual differences in male cognitive performance to variation in paternity arising solely from sexual selection. We therefore ran four standard cognitive assays to quantify five measures of cognitive performance by male mosquitofish (Gambusia holbrooki). Males were then assigned to 11 outdoor ponds where they could compete for females. Females mate many times, which leads to intense sperm competition and broods with mixed paternity. We genotyped 2,430 offspring to identify their fathers. Males with greater inhibitory control and better spatial learning abilities sired significantly more offspring, while males with better initial impulse control sired significantly fewer offspring. Associative and reversal learning did not predict a male’s share of paternity. In sum, there was sexual selection on several, but not all, aspects of male cognitive performance. The authors find that male mosquitofish with greater inhibitory control and better spatial learning ability gain a significantly higher share of paternity than do more impulsive males, suggesting that these cognitive abilities are under direct sexual selection in male mosquitofish.