BackgroundAims

The historical biogeography of the Northern Hemisphere has long been of interest to botanistsbiogeographers. Numerous studies have been devoted to investigating the timing, routedirection of dispersals. However, little is known about how the Northern Hemisphere disjunctions formed after range expansion. Here, we used Leonticeae to investigate how biogeographical processclimatic 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 timesreconstructed ancestral rangeshabitats. Furthermore, we conducted phylogenetic principal component analysis on bioclimatic variablesinferred their major shiftsancestral states.

Key Results

The most recent common ancestor of Leonticeae occupied closed habitats in East AsiaCentral 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,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 expansionsubsequent vicariance driven by niche differentiations in precipitation, in conjunction with Neogene geoclimatic events, might have been jointly responsible for the current distributionendemism of Leonticeae. These findings contribute to our knowledge of the historical biogeography of plants in the Northern Hemisphere.