Phylogenetic evidence for multiple losses of a sexually selected characterin phrynosomatid lizards

The evolution of conspicuous male display ornaments is a common trend in di verse groups of organisms and a continuing challenge to studies of sexual s election. A phylogenetic approach was used to examine macro-evolutionary pa tterns of change in sexually dichromatic display coloration (distinctively coloured belly patches) among 130 lasa of phrynosomatid lizards. The result s showed repeated losses of sexual dimorphism, which occur through losses o f conspicuous male coloration or gains of conspicuous female coloration. Th e frequent loss of male traits is surprising, given that sexual selection p resumably drives their evolutionary origin and maintenance, but is consiste nt with a recently proposed hypothesis suggesting that females may lose res ponsiveness to male traits over macro-evolutionary time-scales. The observa tion of repeated losses of male traits in phrynosomatid lizards land other groups) may have implications for testing among competing models for the ev olution of female preferences. A concentrated changes test showed that chan ges in male display coloration are significantly associated with the use of ground-dwelling habitat, as opposed to rock- or tree-dwelling habitats. Th is result suggests a role for natural selection in the loss of male display traits in phrynosomatid lizards, but habitat type alone may be insufficien t to explain these losses.