The effects of the dispersal ability in the diversification dynamics of Emberizoidea (Aves: Passeriformes)

Understanding how ecological and evolutionary forces shape biodiversity is a core pursuit in macroevolutionary research. Species' dispersal ability significantly impacts their colonization chances and geographic isolation, profoundly influencing species ecology and evolution. Our study delved into the relationship between dispersal ability and speciation rates within Emberizoidea, a diverse group of passerine birds. We used the Hand-Wing Index (HWI) as a morphological proxy for dispersal ability and phylogenetic data for 749 species of Emberizoidea (∼90% of all recognized species for the clade) using trait-dependent diversification models, including continuous-state (QuaSSE) and hidden-states (SecSSE) models. We also applied the correlated speciation and trait rates simulation (Cor-STRATES) framework to assess correlation between HWI evolution and speciation rates. Our findings revealed that speciation in Emberizoidea was not significantly influenced by dispersal ability as estimated by HWI. While QuaSSE models suggested a peak in speciation rates at intermediate HWI values, the best-fit SecSSE model indicated that speciation was driven by unmeasured trait(s) rather than HWI. Moreover, HWI evolution and speciation rates were not correlated, suggesting that wing shape evolution is unrelated to cladogenetic events in Emberizoidea's evolutionary history. Our study challenges the notion that dispersal ability and wing shape drive diversification in birds, particularly in Emberizoidea.