Phylogenetic inference of where species spread or split across barriers

Regional features of geography, such as size or distance, are expected to shape how lineages disperse, go extinct, and speciate. Yet this fundamental link between geographical context and evolutionary consequence has not been fully incorporated into phylogenetic models of biogeography. We designed a model that allows variation in regional features (size, distance, insularity, and oceanic separation) to inform rates of biogeographic change. Our approach uses a Bayesian hierarchical modeling framework to transform regional values of quantitative and categorical features into evolutionary rates. We also make use of a parametric range split score to quantify range cohesion for widespread species, thereby allowing geographical barriers to initiate “range-splitting” speciation events. Applying our approach to Anolis lizards, a species-rich neotropical radiation, we found that distance between regions, especially over water, decreases dispersal rates and increases between-region speciation rates. For distances less than ∼470 km over land, anoles tended to disperse faster than they speciate between regions. Over oceans, the equivalent maximum range cohesion distance fell to ∼160 km. Our results suggest that the historical biogeography of founder event speciation may be productively studied when the same barriers that inhibit dispersal also promote speciation between regions.