Range expansion and climatic niche divergence-driven vicariance shaped historical biogeography of Leonticeae (Berberidaceae) across the Northern Hemisphere

Background and Aims The historical biogeography of the Northern Hemisphere has long been of interest to botanists and biogeographers. Numerous studies have been devoted to investigate the timing, route, and direction of dispersals. However, little is known about how the Northern Hemisphere disjunctions formed after range expansion. Here, we used Leonticeae to investigate how biogeographic process and climatic niche divergence shaped the current distribution patterns of Northern Hemisphere plants. Methods We used ten DNA loci to reconstruct a phylogeny including ∼79% species of Leonticeae. Within the phylogenetic framework, we estimated divergence times and reconstructed ancestral ranges and habitats. Furthermore, we conducted phylogenetic principal component analysis on bioclimatic variables and inferred their major shifts and ancestral states. Key Results The most recent common ancestor of Leonticeae occupied closed habitats in East Asia and Central Asia at ca. 22 Ma. Caulophyllum dispersed from East Asia to eastern North America at ca. 22–7 Ma, followed by a vicariance event. Leontice split from Gymnospermium at ca. 15 Ma, along with the shift from closed to open habitats. Gymnospermium dispersed from East Asia to Central Asia at ca. 13–10 Ma, and then independently colonized East Mediterranean twice during the late Miocene-Pliocene. Marked divergences of climatic niches, especially in precipitation, between the disjunctly distributed sister species/lineages were found. Conclusions East Asia serves as a source area for species diversity of the Northern Hemisphere in Leonticeae. Range expansion and subsequent vicariance driven by niche differentiations in precipitation, in conjunction with Neogene geoclimatic events, might have been jointly responsible for the current distribution and endemism of Leonticeae. These findings contribute to our knowledge on the historical biogeography of plants in the Northern Hemisphere.