Female-specific color is a signal of quality in the striped plateau lizard (Sceloporus virgatus)

Stacey L. Weiss, University of Puget Sound


Recent theoretical and empirical studies confirm that male mate choice and/or female–female mate competition can be expressed in the absence of sex-role reversal. Such reproductive patterns may select for the evolution of female traits that indicate female phenotypic or genotypic quality among non–role-reversed species. Although attention to the evolution and function of female ornaments is increasing, additional focus is needed on female-specific ornaments (those not expressed in conspecific males) and on nonavian systems in order to gain a broad understanding of how selection acts directly on ornamentation of female animals. In the striped plateau lizard, Sceloporus virgatus, only females develop orange throat patches during the reproductive season. The color peaks in expression near the time of ovulation and appears to stimulate male courtship. Here, I examine whether this female-specific ornament can be used by males to reliably assess female phenotypic quality. Using multivariate regression analyses, I show that the area of the orange color patch predicts body condition and mite load, the chroma (i.e., saturation) of the color patch predicts body size, and both patch area and chroma reliably predict average egg mass. Thus, female reproductive color may function as a condition-dependent signal, indicating phenotypic quality to potential mates.