Divergent roles for multiple sexual signals in a polygynous lizard

Abstract

Summary An unresolved issue in sexual selection concerns the utility of multiple sexual signals that are used simultaneously during displays. We examined male lizards (Urosaurus ornatus) that exhibit two colourful ornaments (throat patch and belly patch) during territorial displays. Populations of Urosaurus ornatus can be polymorphic in throat coloration, and previous studies have shown that the morphs differ in behavioural aggression. We assume that throat coloration correlates with behavioural aggression in our population, as for other populations of U. ornatus. We show that these different morphs do not differ significantly in morphological shape or bite force, a key aspect of fighting capacity. However, by contrast, the size of the belly patch is a significant predictor of maximum bite force, which is a predictor of dominance in other lizards. We suggest that belly patch size and throat patch coloration are largely exclusive in that dominant individuals can exhibit small belly patches and low bite forces, whereas subordinate individuals can have large belly patches and high bite forces. Thus, embedded within the same male lizard display are divergent sexual structures that signal different traits, implying that the possession of multiple sexual signals within animals may be favoured by selection.