Sexual selection and taxonomic diversity in passerine birds

Abstract
Many authors have suggested that sexual selection by female choice may increase the speciation rate and hence generate taxonomic diversity. Using sister taxa comparisons, we find a significant positive correlation between the proportion of sexually dichromatic species within taxa of passerine birds, and the number of species in those taxa. Theory predicts this result if sexual dichromatism in passerines has evolved through the action of female choice.