Does dichromatism variation affect sex recognition in dwarf geckos?

Abstract

As visual signals play a role in sex recognition among dwarf geckos (Sphaerodactylus), behavioral adaptations may counterbalance the lack of visual recognition cues in monochromatic species. Data from social interactions in captivity of 10 species were analyzed to evaluate a qualitative model, developed to explain the influences of dichromatism variation on behaviors related to sex recognition. The model, based on recognition theory, aimed to link the changes in behavioral mecanisms triggered by loss of recognition cues with the fitness consequences of different tactics to approach a conspecific of unknown sex; it suggested that uncertainty about conspecifics’ sex in monochromatic species could favor the display of ambivalent signals due to multiple potential advantages: assisting recognition by eliciting homotypical behaviors in social partners, solving fitness-reducing conflicts faster, reaping the benefits when meeting conspecifics of opposite sex, reducing cost associated with courtship displays and benefiting females by providing a reliable male quality indicator. In agreement with the model, males used courtship and threat signals unequivocally in dichromatic species, ambivalently in monochromatic species, and conditionally on opponent phenotype in species with two male morphs. Loss of visual recognition cues is suggested as an important and probably widespread source for the origin of similarity between sexual and aggressive signals.