The evolution of sexual dimorphic traits is thought to be driven by selective pressures, such as sexual selection, fecundity, and inter-sexual resource selection. Within the Galliformes, the elaboration of these particular traits is emphasized in dimorphic species. Understanding the evolution of these characteristics, and their potential role in speciation dynamics, will give insight into the interplay between sexual selection, evolution and, ultimately, extinction within highly dimorphic lineages. Although the gains and losses of these traits are well-characterized, the evolution of dimorphic traits and their impact on the rates of diversification remain largely unknown. Here I evaluate a set of state speciation and extinction (SSE) models to nine separate sexual dimorphic traits to analyze the potential for trait-dependent diversification. Several models I examined included “hidden states” that account for rate heterogeneity and allows for detection of true signals of trait-dependent diversification from diversification shifts that are completely independent of the trait of interest.
Results/Conclusions
My analyses revealed that five of the nine dimorphic traits are associated with meaningful increases in net diversification. Importantly, my results show that species which have accrued all five of these traits are correlated with both higher speciation and extinction rates, indicating that sexual dimorphism is associated with “boom and bust” macro-evolutionary dynamics. I will discuss future work that will focus on the correlation between social breeding behaviors and the evolution of highly specialized dimorphic characters and their risk of extinction, with the ultimate goal of informing conservation practices for at risk species.