Climate heterogeneity shapes phylogeographic pattern of Hippophae
gyantsensis (Elaeagnaceae) in the East Himalaya-Hengduan Mountains
Abstract
The interaction of recent orographic uplift and climate heterogeneity
acted as a key role in the East Himalaya-Hengduan Mountains (EHHM) has
been reported in many studies. However, how exactly the interaction
promotes clade diversification remains poorly understood. Here, we both
studied genetic structure of the chloroplast trnT-trnF region and 11
nuclear microsatellite loci in Hippophae gyantsensis and examined what
role geological barriers or ecological factors play in the spatial
genetic structure. The results showed that this species had a strong
east-west phylogeographic structure, with several mixed populations
identified from microsatellite data in central location. The
intraspecies divergence time was estimated to about 3.59 Ma,
corresponding well with the recent uplift of the Tibetan Plateau.
Between the two lineages there was significant climatic differentiation
without geographic barriers. High consistency between lineage
divergence, climatic heterogeneity and Qingzang Movement demonstrated
that climatic heterogeneity but not geographic isolation drives the
divergence of H. gyantsensis, and the recent regional uplift of the QTP,
as the Himalayas, create heterogeneous climates by affecting the flow of
the Indian monsoon. The east group of H. gyantsensis experienced
population expansion c. 0.12 Ma, closely associated with the last
interglacial interval. Subsequently, a genetic admixture event between
east and west groups happened at 26.90 ka, a period corresponding to the
warm inter-glaciation again. These findings highlight the importance of
the Quaternary climatic fluctuations in the recent evolutionary history
of H. gyantsensis. Our study will improve the understanding of the
history and mechanisms of biodiversity accumulation in the EHHM region.