The Ontogeny of a Variable Social Badge: Throat Color Development in Tree Lizards (Urosaurus ornatus)

Abstract

Two populations of tree lizards (Urosaurus ornatus) that differ in morphological and social traits, were used in a comparative study examining the ontogenetic development of throat coloration. Adult males from the Aguirre Spring population exhibited monomorphic throat coloration while Donia Ana males were polymorphic. In a separate study, Aguirre Spring males were found to be in certain respects more aggressive than Dona Ana males. Juvenile males and females from both populations first exhibit orange throat color. Adult Doiia Ana females always retain the orange throat coloration but Aguirre Spring females may either retain orange or develop yellow throats. In males from both populations throat badge ontogeny involves a series of throat color changes while ventral belly coloration initially appears as its final hue. This suggests that ontogenetic color change and polymorphic adult coloration serve social functions. Orange throat coloration seen in females and young males may serve to inhibit aggression from adult males. Most dominant Aguirre Spring males have throat colors that are seen late in the developmental sequence suggesting that mature colors (i.e., blue and blue-green) are more socially dominant and are favored by sexual selection.