Chloroplast haplotypes and main haplotypes of nrITS clones of Gentiana crassicaulis

The Himalaya-Hengduan Mountain region is one of the hotspots of
biodiversity research. The uplift of the Qinghai-Tibetan Plateau (QTP) and
the Quaternary glaciation caused great environmental changes in this
region, and the responses of many species in the QTP to the Quaternary
climate are still largely unknown. The genetic structure and
phylogeographical history of Gentiana crassicaulis Duthie ex Burk, an
endemic Chinese alpine species in this area, were investigated based on
four chloroplast fragments and internal transcribed spacer region of the
nuclear ribosomal DNA (nrITS) sequences of 11 populations. The populations
with highly diverse chloroplast haplotypes were mainly found at the edge
of the QTP. There were two main haplotypes of nrITS clones, one shared by
the Yunnan and Guizhou populations, and the other by the remaining
populations. The population with the highest diversity was the Gansu
population, located at the edge of the plateau. Based on molecular dating,
the diversification of G. crassicaulis at the edge of the plateau occurred
before the Last Glacial Maximum (LGM), and the species may have completed
its expansion from the edge to the platform. Ecological Niche Models were
conducted to predict the distributional ranges of G. crassicaulis at
present, during the LGM, and during the last interglacial (LIG) period.
The results demonstrated that G. crassicaulis survived on the QTP platform
and at the edge during the LGM but afterward retreated from the platform
to the southern edge, followed by expansion to the platform.