Phylogeographic structure of Hippophae tibetana (Elaeagnaceae) highlights the highest microrefugia and the rapid uplift of the Qinghai-Tibetan Plateau

Abstract

The uplift of the Qinghai-Tibetan Plateau (QTP) dramatically changed the topography and climate of Asia and affected the biodiversity of the plateau and its adjacent areas. However, the effects of the uplift on the dispersal, differentiation and adaptation of plants remain a puzzle when the date and processes of the uplift cannot be determined with certainty and the impacts of the Quaternary glaciations on plants on the QTP are unknown. To clarify the relationships among plants on the QTP with the plateau uplift and the Quaternary glaciations, the cpDNA trnT-trnF regions of 891 individuals from 37 populations of Hippophae tibetana, endemic to the QTP, were sequenced in the present study. A total of 50 haplotypes were found and a strong phylogeographic structure was revealed (N(ST) = 0.854, G(ST) = 0.611, N(ST) > G(ST), P < 0.01). The results show that three main lineages of the present populations of H. tibetana occupy the western, the middle, and the eastern geographical range, respectively, and their divergence time dates back to 3.15 Ma before present. Of 50 haplotypes, 33 (66%) are private haplotypes, which are restricted to single populations. These private haplotypes are scattered throughout the present geographical range of H. tibetana and originated from multiple differentiations in many lineages during more than 1.0 Ma period, strongly suggesting that multiple microrefugia of H. tibetana existed throughout the present geographical range during the last glacial maximum (LGM) and even earlier glaciations. Additionally, the average elevation of present populations is over 4500 m in the west and the equilibrium-line of glaciers in the LGM was 500-300 m lower than present in the major interior part of the plateau suggesting that at most sites in the west, LGM microrefugia of H. tibetana may have been above 4000 m above sea level, the highest of all known refugia. Moreover, the divergence times among and within the three lineages and their distinct distributions as well as dispersal barriers support the theory of the recent and rapid uplift of the QTP. The rapid uplift of the plateau within the last 3.4 Ma and the associated environmental changes may have affected the dispersal and differentiation of H. tibetana and shaped its phylogeographic structure.

Patterns of chloroplast DNA variation in Cycas debaoensis (Cycadaceae): conservation implications

“…In addition, based on mismatch distribution analysis and neutrality tests, we found no evidence of long-distance dispersal or population expansion. As some other ancient and drought-resistant species in southwest China (Opgenoorth et al 2010;Wang et al 2010), C. debaoensis may have been able to endure cold conditions during the glacial periods and may have remained in multiple microrefugia throughout its current range. The cpDNA haplotypes might represent ancient polymorphism rather than recent gene flow and expansion (Schaal et al 1998).…”

Phylogeographic pattern of Populus cathayana in the southeast of Qinghai-Tibetan Plateau of China revealed by cpSSR markers

“…They found the plateau edge was likely a large refugium during the last glacial period and that the marked population differentiation exhibited by the species in its refugium was likely, due to high mountain barriers. Recent studies conducted by organelle DNA also came to similar conclusions, that plant populations from the southeastern part of the Qinghai-Tibetan Plateau had higher genetic diversity and higher population differentiation than those from other areas and that there were multiple refugia for plant species during the Quaternary period glaciations (Meng et al 2007, Li et al 2010, Wang et al 2010.…”

Microrefugia and Shifts of Hippophae tibetana (Elaeagnaceae) on the North Side of Mt. Qomolangma (Mt. Everest) during the Last 25000 Years

“…It is one of the shrubs to occur at the highest altitudes [44], growing up to ∼5200 m asl. Our previous study [43] investigated the phylogeography of H. tibetana and found that three main lineages (A, B, and C) of the present populations of this species occupy the middle, the western, and the eastern parts of its geographical range, respectively. Based on the distribution of a large number of private haplotypes, we concluded that H. tibetana had multiple LGM microrefugia on the Plateau and inferred that the Rongbuk Valley, north of Mt.…”

“…H. tibetana is a small dioecious shrub propagated by seeds or by horizontal roots [42]. It is endemic to the Qinghai-Tibet Plateau (QTP) and ranges from the west Himalaya to the east-north QTP [43]. In the eastern plateau, H.tibetana occurs in the lowlands and in alpine meadows at an altitude below 4000 m, but in the central plateau and the Himalayas, it has a fragmented distribution along several valleys.…”