Abstract
Qinghai-Tibetan Plateau (QTP) is an important biodiversity hub, which is very sensitive to climate change. Here in this study, we investigated genetic diversity and past population dynamics of Lancea tibetica (Mazaceae), an endemic herb to QTP and adjacent highlands. We sequenced chloroplast and nuclear ribosomal DNA fragments for 429 individuals, collected from 29 localities, covering their major distribution range at the QTP. A total of 19 chloroplast haplotypes and 13 nuclear genotypes in two well-differentiated lineages, corresponding to populations into two groups isolated by Tanggula and Bayangela Mountains. Meanwhile, significant phylogeographical structure was detected among sampling range of L. tibetica, and 61.50% of genetic variations was partitioned between groups. Gene flow across the whole region appears to be restricted by high mountains, suggesting a significant role of geography in the genetic differences between the two groups. Divergence time between the two lineages dated to 8.63 million years ago, which corresponded to the uplifting of QTP during the late Miocene and Pliocene. Ecological differences were found between both the lineages represent species-specific characteristics, sufficient to keep the lineages separated to a high degree. The simulated distribution from the last interglacial period to the current period showed that the distribution of L. tibetica experienced shrinkage and expansion. Climate changes during the Pleistocene glacial-interglacial cycles had a dramatic effect on L. tibetica distribution ranges. Multiple refugia of L. tibetica might have remained during the species history, to south of the Tanggula and north of Bayangela Mountains, both appeared as topological barrier and contributed to restricting gene flow between the two lineages. Together, geographic isolation and climatic factors have played a fundamental role in promoting diversification and evolution of L. tibetica.
Highlights
The Qinghai-Tibetan Plateau (QTP) is one of the largest and youngest plateaus in the world, formed by several uplift events after the collision of the Indian tectonic plate with the Asian plate, about 40 Ma (Guo et al, 2002; Spicer et al, 2003)
Our study provides an important advance in knowledge of the population dynamics of endemic species on the QTP
We identified a total of 19 haplotypes (A–S), which were asymmetrically distributed across the 29 populations (Figure 2)
Summary
The Qinghai-Tibetan Plateau (QTP) is one of the largest and youngest plateaus in the world, formed by several uplift events after the collision of the Indian tectonic plate with the Asian plate, about 40 Ma (million years ago) (Guo et al, 2002; Spicer et al, 2003). Other scholars, such as Renner (2016) and Spicer (2017), suggest that there was no obvious impact on the East Asian monsoon from the uplifting of the QTP, even they hold the opinion that uplift having reached average heights of 4–5 km since the mid-Eocene. These climatic oscillations did affect the demography of some species, leading to their range shifting or extinction. The harsh climate of this region may have improved the adaptability of some local organisms (Davis and Shaw, 2001; Hewitt, 2004; Wan et al, 2016)
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