Sexual selection and the evolution of male and female cognition: a test using experimental evolution in seed beetles

Abstract

\"The mating mind hypothesis\", originally aimed at explaining human cognition, holds that the socio-sexual environment shapes cognitive abilities among animals. Similarly, general sexual selection theory predicts that mate competition should benefit individuals carrying \"good genes\" with beneficial pleiotropic effects on general cognitive ability. However, few experimental studies have evaluated these related hypotheses due to difficulties of performing direct tests in most taxa. Here we harnessed the empirical potential of the seed beetle study system to investigate the role of sexual selection and mating system in the evolution of cognition. We evolved replicate lines of beetle under enforced monogamy (eliminating sexual selection) or polygamy for 35 generations and then challenged them to locate and discriminate among mating partners (male assays) or host seeds (female assays). To assess learning, the same beetles performed the task in three consecutive rounds. All lines learned the task, improving both within and between trails. Moreover, polygamous males outperformed monogamous males. However, there were no differences in the rate of learning between males of the two regimes, and polygamous females showed no improvement in host search, and even signs of reduced learning. Hence, while sexual selection was a potent factor that increased cognitive performance in mate search, it did not lead to the general increase in cognitive abilities expected under the \"mating mind\" hypothesis or general \"good genes\" theory. Our results highlight sexually antagonistic (balancing) selection as a potential force maintaining genetic variation in cognitive traits.