Understanding the structure of local communities requires integration of the study of local dynamics with broader studies of biogeography. This is the case because the species present in local assemblages reflect both local interactions and the composition of the regional species pool. It becomes especially important to consider the broader biogeographic context when conducting comparisons of phylogenetic diversity among areas, even within regions. As such comparisons scale up, especially to comparisons among biogeographic regions, differential rates of diversification become a key factor underlying patterns of phylogenetic diversity. I will highlight several such cases as a means of exploring how best to integrate historical biogeography into studies of community assembly.