Meeting Abstract
Sexual selection by female mate choice is a major driving force in speciation. Since sexually selected male traits are often plastic, phenotypic plasticity and sexual selection are thought to jointly facilitate diversification when initially plastic sexual traits undergo genetic divergence by sexual selection. However, sexual selection may also promote plasticity. The resulting increased plasticity can then shield populations from the effects of selection, thereby inhibiting genetic divergence. We show that a combination of mate choice and male-male competition can maintain extreme phenotypic plasticity in a sexually selected male trait. In the cichlid species Astatotilapia burtoni, males are either blue or yellow. We show that adult males frequently change between yellow and blue color with blue males showing more color plasticity than yellow males. We then show that this remarkable plasticity in male color is directly influenced by the social environment: more males express yellow coloration in environments with more intense male-male competition. In staged combats, yellow males are more successful competitors than blue males, which could explain the higher proportion of yellow morphs in more competitive environments. However, females express a strong sexual preference for blue males. The trade-off between different components of sexual selection could promote the persistence of plastic coloration. Our work suggests that sexual selection may maintain phenotypic plasticity and potentially inhibit genetic diversification in sexually selected traits.
