Sexual selection on body size and secondary sexual characters in 2 closely related, sympatric chameleons in Madagascar

In polygynous mating systems, sexual selection can drive the evolution of male characters beneficial to winning fights for mates (intrasexual selection), for improving the mating success of males through mate choice (intersexual selection), or both. However, it may be difficult to disentangle the relative contributions of intra and intersexual selection on multiple traits that may be of dual utility. We used field arena trials to determine which morphological traits best explained male fighting ability and male mating success in 2 species of chameleons in Madagascar, Furcifer labordi and Furcifer verrucosus. In F. labordi, male fighting success was best predicted by body size and size-corrected shorter rostral appendages and male mating success was best predicted by width of the rostral appendage and body size. In F. verrucosus, we found strong intrasexual selection for increased male body size and fewer counted dorsal cones, a trait that may correspond to increased age and experience. Although females in this species are generally passive toward courting males, male mating success with potentially receptive females is highly variable. Fewer counted dorsal cones and larger size-corrected casque height best explained male mating success; traits that may be selected by the female and/or correlated with increased age and experience. Although difficult to determine the relative contributions of intra and intersexual selection on traits with dual benefits (both fighting and mate choice), we documented both types of selection on body size and secondary sexual characters in these 2 chameleon species.