• comparative methods;
  • sensory drive;
  • signalling;
  • social selection;
  • species recognition

Male ornaments have been the subject of numerous studies on sexual selection and communication, although female ornaments have garnered substantially less study, even though female ornaments are well developed in some species. The factors that have propelled the evolution of elaborate ornaments in females are poorly understood but may include genetic correlations between the sexes, social selection, sensory drive or species recognition. We used simulation-based comparative methods and a newly estimated phylogeny to test these four hypotheses to explain female ornamentation within the diverse neotropical lizard genus Anolis. We found support for the sensory drive hypothesis and the social selection hypothesis; the female dewlap was larger in species that use more arboreal habitats, as well as in species where the sexes were less dimorphic. We did not find support for the genetic correlation hypothesis or the species recognition hypothesis. We propose that the size of the female dewlap may evolve in response to sensory drive differentially affecting species in different habitats, as well as social selection such as male mate choice or intrasexual competition for territory among females. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106, 191–201.