Diversification rates in Berberis

The Latitudinal Diversity Gradient (LDG) is one of the most common observed and studied patterns in ecology. The study of the uneven distribution of species across the globe has nourished a body of ecologic theories, with several hypotheses proposed in order to explain this pattern. LDG has been suggested to be caused by higher speciation rates in the tropics compared with temperate regions. In order to test this hypothesis, a phylogeny of the mostly Northern Temperate but also South American genus Berberis was constructed and dated. Nuclear ITS and chloroplast ndhF regions were used to build a molecular phylogeny representing most of the sections of Berberis found in the Northern Hemisphere and South America. Bayesian diversification analyses were done using the time-calibrated phylogeny. Our results suggest a significant rate shift in diversification near the base of Berberis, with no further increase in speciation rates towards the tropics. The evidence suggests no significant differences in speciation for Berberis between tropical and temperate zones. Further studies will be required to test whether higher rates detected in the Himalayan clade are linked to the mountain uplift.