Out of the Qinghai–Tibet Plateau: evidence for the origin and dispersal of Eurasian temperate plants from a phylogeographic study of Hippophaë rhamnoides (Elaeagnaceae)

Abstract

Summary• Numerous temperate plants now distributed across Eurasia are hypothesized to have originated and migrated from the Qinghai-Tibet Plateau (QTP) and adjacent regions. However, this hypothesis has never been tested through a phylogeographic analysis of a widely distributed species. Here, we use Hippophaë rhamnoides as a model to test this hypothesis.• We collected 635 individuals from 63 populations of the nine subspecies of H. rhamnoides. We sequenced two maternally inherited chloroplast (cp) DNA fragments and also the bi-paternally inherited nuclear ribosomal ITS.• We recovered five major clades in phylogenetic trees constructed from cpDNA and internal transcribed spacer (ITS) sequence variation. Most sampled individuals of six subspecies that are distributed in northern China, central Asia and Asia Minor ⁄ Europe, respectively, comprised monophyletic clades (or subclades) nested within those found in the QTP. Two subspecies in the QTP were paraphyletic, while the placement of another subspecies from the Mongolian Plateau differed between the ITS and cpDNA phylogenetic trees.• Our phylogeographic analyses supported an 'out-of-QTP' hypothesis for H. rhamnoides followed by allopatric divergence, hybridization and introgression. These findings highlight the complexity of intraspecific evolutions and the importance of the QTP as a center of origin for many temperate plants.

Phylogeography of Rhodiola kirilowii (Crassulaceae): A Story of Miocene Divergence and Quaternary Expansion

“…More than ten plant species in the QTP and adjacent areas have been studied, focusing on their geographic patterns of genetic diversity. The results have confirmed that the Hengduan Mountains were an important refugium during the Quaternary ice age [26]–[31], although it is suspected that some species survived in ice-free areas on the plateau itself during the glaciation [32]–[34]. Many plant species distribute from the HM to northern China (e.g., Rhodiola kirilowii (Regel) Maxim., Incarvillea sinensis Lam., Caragana jubata (Pall.)…”

Evolutionary history of Orinus thoroldii (Poaceae), endemic to the western Qinghai-Tibetan Plateau in China

“…Oscillation-associated changes in the distribution of plants in the QTP were first detected when their pollen was recovered and examined (Tang and Shen, 1996). Later phylogeographical studies of a few representative species confirmed such distributional dynamics (Wang et al, 2009a;Tian et al, 2011;Jia et al, 2012). For example, some species that were sensitive to these climate changes retreated from eastern refugia during the glacial stage and re-colonized the central plateau platform (e.g., Zhang et al, 2005;Chen et al, 2008;Yang et al, 2008).…”

“…The QTP and its adjacent regions comprise a major hotspot for global biodiversity, supporting numerous endemic species (Wu, 1988;Mittermeier et al, 2005). This wide variety of species has arisen because of rapid and extensive uplifts of the QTP plus climatic oscillations during the Pleistocene that promoted allopatric speciation (Wang et al, 2009a,b;Jia et al, 2012). Furthermore, because the QTP was most sensitive and vulnerable to the Pleistocene global climate (Zhang, 1983;Raymo and Ruddiman, 1992;Zhan, 2005), growth, reproduction, and survival of existing species have depended greatly upon exposure to suitable temperatures (Zheng, 1996;Ni, 2000;Thompson et al, 2000).…”

Responses of two endemic species of Hippophae at the Qinghai-Tibet Plateau to elevated CO₂ concentration

“…Due to its nitrogen-fixing characteristics and its importance in forest restoration, medicine, and food, this genus has been attracting more attention in the recent years (Lian 2000, Chen et al 2003, Cheng et al 2009, Jia et al 2012. In this genus, H. gyantsensis and H. rhanmoides ssp.…”