Passerine sister clade comparisons reveal variable macroevolutionary outcomes of interhemispheric dispersal

Dispersal events offer a unique window into macroevolutionary processes. While several hypotheses predict alternative outcomes from such events, many empirical studies have been limited in geographic and phylogenetic scale. Here, we tested some of these hypotheses by comparing an assemblage of 16 oscine passerine clades, representing independent dispersal events into the Western Hemisphere, to their sister clades in the Eastern Hemisphere. We also compared the diversity of this assemblage of clades to an older, incumbent passerine clade in the Western Hemisphere, the suboscines. We tested for ecological opportunity and incumbency-mediated constraints versus neutrality by integrating estimates of clade-specific morphological disparities with models of multivariate regimes of trait evolution. While there was no consistent outcome of oscine dispersal and macroevolution in the Western Hemisphere relative to their Eastern Hemisphere sister groups, most clades supported a role for ecological ...