Phylogenetic Tests of Alternative Intersexual Selection Mechanisms: Trait Macroevolution in a Polygynous Clade (Aves: Pipridae)

Alternative mechanisms of intersexual selection yield distinct macroevolutionary predictions about the magnitude and patterns of trait and repertoire diversity in clades exposed to persistent intersexual selection. Phylogenetic analyses of the evolution of lek display elements and secondary sexual plumages in manakins (Aves: Pipridae) were conducted to test these predictions and determine which sexual selection mechanisms may have had a predominant role in the evolution of traits within a clade of lekking species. The diverse trait repertoires of manakins are composed of independent, hierarchically distributed (historically nested), behavioral, and morphological novelties. In comparison with the closely related, predominantly monogamous tyrant flycatchers (Tyrannidae), the diversity of manakin traits and trait repertoires is explosive, indicating that manakin traits have evolved by an unconstrained evolutionary mechanism. The macroevolutionary patterns in manakin traits are consistent with the predictions of the Fisherian and broad sensory bias mechanisms, but they are not consistent with the predictions of the indicator, direct selection, species isolation, or sensory drive mechanisms. The diverse repertoires and hierarchically distributed traits in the lekking manakin clade indicate that Fisherian selection may have played an important role in diversification of secondary sexual traits in other groups of polygynous animals.