Aim

The Qinghai–Tibet Plateau (QTP) harbours high levels of species diversityendemism,multiple out-of-QTP dispersal routes have been put forward. However, whether different dispersal directions out of the QTP resulted in contrasting evolutionary trajectories remains unknown. Here, we use the sister genera CalathodesTrollius (Ranunculaceae) as an ideal model to investigate the out-of-QTP diversification patterns.

Location

The Northern Hemisphere.

Taxon

CalathodesTrollius (Ranunculaceae).

Methods

We sampled all four species of Calathodes38 species of Trollius to reconstruct a near-complete species-level phylogeny based on 12 molecular loci from the nuclearplastid genomes. Within the phylogenetic framework, divergence times, ancestral rangesdiversification rates were estimated,ancestral habitat, elevationclimate niche were inferred.

Results

The most recent common ancestor of CalathodesTrollius occupied the QTP at ~8 Ma. Calathodes migrated eastward from the QTP to subtropical mainland China at ~4 Mathen further to Taiwan at ~0.5 Ma. Trollius dispersedNorth Asia at ~6 Mafurther reached Northeast Asia, Japan, Taiwan, EuropeNorth America. Net diversification rates of subtropical CalathodesNorth Asian Trollius clades were 0.280.54 My⁻¹, respectively. Calathodesits subtropical clade both prefer the middle-elevation closed, warm,humid habitats, while Trolliusits North Asian clade inhabit open, cold,dry areas.

Main Conclusions

CalathodesTrollius both originated in the QTP in the late Mioceneexhibited long-term habitatclimatic niche conservatism. The distinct out-of-QTP dispersal directions in the two genera probably resulted in their subsequent different diversification patterns, associated with the conservatism in habitat-climate-related niches. Our study suggests the QTP serves as an important source of Northern Hemisphere biodiversityadvances the knowledge of how distinct dispersal directions out of the QTP resulted in contrasting evolutionary trajectories