Meeting Abstract
In developing his theory of sexual selection, Darwin treated the ornamentation of females as a non-adaptive byproduct of sexual selection on males and the transmission of male phenotypes to females via the “laws of inheritance”. Nearly a century and a half later, the extent to which the constraints of shared inheritance contribute to the expression and co-evolution of ornaments in both sexes remains largely uncertain. Here, we provide the first quantitative-genetic analysis of a sexually dimorphic ornament that has figured prominently in studies of behavioral ecology and sexual selection – the brightly colored dewlap of Anolis lizards. Using a paternal half-sibling breeding design in a captive population of Bahamian brown anoles (Anolis sagrei), we show that most aspects of this complex social signal exhibit significant additive genetic variance, including dewlap size, hue, and brightness measured from photographs and red chroma measured from reflectance spectra. Whereas sexually monomorphic components of the dewlap, such as hue, exhibit high and significant between-sex genetic correlations, sexually dimorphic components, such as size and brightness, exhibit reduced between-sex genetic correlations that do not differ from zero. From a multivariate perspective, within- and between-sex genetic variance-covariance matrices reveal a combination of shared and sex-specific features underlying the genetic architecture of the Anolis dewlap. We discuss these results in the broader context of genetic constraints on the evolution of sexually dimorphic phenotypes and implications for the evolution of male ornaments by various models of sexual selection and their assumptions about heritability of male ornaments.
