The evolution of performance-based male fighting ability in Caribbean Anolis lizards

Despite the empirical and theoretical attention paid to the role of sexual signals in resolving agonistic interactions between conspecific males, few studies have applied a comparative perspective, particularly across species that vary in combat intensity. We investigated the relative roles of a male sexual signal (dewlap size) and whole-organism performance capacity (bite force) on male combat outcomes in nine species of Caribbean Anolis lizards that differ markedly in territoriality, as indicated by sexual size dimorphism. We found that (1) dewlap size was generally an honest signal of bite force in dimorphic but not less dimorphic species; (2) maximum bite force consistently predicted male combat success in dimorphic but not less dimorphic species; (3) in contrast to a priori predictions, dewlap size significantly predicted male combat success in less dimorphic but not dimorphic species; and (4) the incidence of biting but not dewlapping increases as species become more dimorphic. These findings suggest that more dimorphic (and hence more territorial) species escalate to biting during fights more readily compared with less territorial species. The ecological and behavioral qualities of species may therefore modify both the shape and the size of sexually selected traits as well as the nature of the information those traits convey.