Multivariate Sexual Dimorphism, Sexual Selection, and Adaptation in Greater Antillean Anolis Lizards

Abstract

Sexual variation in body form is a common phenomenon in the natural world. Although most research has focused on dimorphism in size, examination of differences in shape can provide insight into ecological factors that may differ in importance to the sexes. In this study, we investigated the patterns of body shape dimorphism in 15 species of Greater Antillean Anolis lizards and investigated whether these patterns can be explained by allometry, phylogenetic effect, or sexual differences in habitat use. We found extensive shape and ecological variation between males and females. Previous studies have been conducted on males only; we found that females have also evolved morphologies to match their habitats. However, we concluded that adaptive patterns differ for the sexes and that interspecific ecological variation is related more strongly to shape than to size for each sex. Previous studies on males have revealed repeated convergent evolution of morphology to habitat types (termed “ecomorphs”). Here, we found that ecomorphs also differ in the magnitude and direction of shape dimorphism. These results cannot be accounted for by allometric scaling or by phylogenetic similarity (regardless of assumptions regarding evolutionary process); they support previous studies that have found important life-history differences for species of different habitat types. We found some evidence for independent adaptation of the sexes, but with more complex ecological patterning occurring between sexes than can be explained by sexual selection alone. Consequently, some combination of functional differences and sexual selection is required.