Sexually selected sexual selection: Can evolutionary retribution explain female ornamental colour?

By preferring mates with increasingly costly ornaments or courtship displays, females cause an escalation of male reproductive costs. Such increased costs should promote male selectivity based on fecundity-linked female attributes, leading to female ornamentation in species with traditional sex roles. Consequently, female ornamentation should evolve more frequently in taxa where male reproduction is costly than in comparable taxa where it is cheaper. We assessed the prevalence of female ornamental colouration in two clades of viviparous cyprinodontid fish: the Goodeinae, where stringent female choice imposes male mating costs, and the Poeciliinae, whose males can circumvent female mate choice. We found that although in the Poeciliinae female ornamental colour is a correlated, but paler version of male coloration, females of the Goodeinae often display vivid ornamental colours that are distinct from those of males. Thus, male and female ornaments are not (phylo)genetically correlated in the Goodeinae. Furthermore, phylogenetic signal on male and female colour is clearly detectable in the Poeciliinae, but absent in the Goodeinae, suggesting that ornamental colour of males and females in the latter may be the consequence of selection. Given that enforceable female choice has promoted male ornaments, we propose that evolutionary retribution has promoted distinct female ornaments in the Goodeinae.