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 investigating 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 biogeographical 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 ∼22 Ma. Caulophyllum dispersed from East Asia to eastern North America at ∼22–7 Ma, followed by a vicariance event. Leontice split from Gymnospermium at ∼15 Ma, along with the shift from closed to open habitats. Gymnospermium dispersed from East Asia to Central Asia at ∼13–10 Ma, and then independently colonized the 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 of the historical biogeography of plants in the Northern Hemisphere.