A complete understanding of the adaptive significance of sexual dimorphism requires understanding both the male and female perspective. Males across taxa display elaborate morphological traits that increase their fitness directly via female mate-choice or male-male competition. Recently, female signals have begun to garner substantial scientific interest. In many cases, female ornaments are likely to be adaptive rather than a selectively neutral byproduct of genetic correlations between the sexes. Many of the same evolutionary selection pressures associated with male ornament evolution may also apply to females, but it is also likely that female-specific selection pressures also contribute to promote female signals. Here, we test two non-mutually exclusive hypotheses exploring the adaptive significance of female coloration in white-shouldered fairywrens (Malurus alboscapulatus): Male mate choice and female-female competition. In two populations that vary in the extent of sexual dichromatism (i.e., female, but not male, ornamentation varies), we used a reciprocal experimental design to test how varying female plumage mounts are perceived by wild male and female fairywrens. Specifically, we focus on if males between populations that vary in sexual dichromatism perceive females in a mating versus competitive context and if ornamented females are on average more hostile toward female intruders than unornamented females
Results/Conclusions
Males do not vary their aggressive between populations when presented with mounts of both sexes simultaneously, whereas ornamented females are more aggressive than unornamented females in similar simulated intrusion contexts. Our preliminary findings here suggest that, when female mounts are presented alone with a female song, males attempt to court females. Remaining field work completed in Spring 2018 will reveal if male behavior is consistent between female phenotypes or if males will view females in a competitive context (if female ornamentation is a product of competition rather than male mate choice). In addition, preliminary data reveal that ornamented females are more aggressive towards unornamented female mounts than they are their own. Thus far, we have found results consistent with the idea that male mate choice and female intrasexual competition both influence female ornamentation between divergent populations. These results advance our collective understanding of the adaptive significance of divergent patterns of sexual dichromatism and how males and females individually perceive female ornamentation.