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Population genetic differentiation and taxonomy of three closely related species of saxifraga (Saxifragaceae) from southern tibet and the Hengduan mountains

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posted on 2018-01-09, 10:16 authored by Qing-Bo Gao, Yan Li, Zhuo-Ma Gengji, Richard J Gornall, Jiu-Li Wang, Hai-Rui Liu, Liu-Kun Jia, Shi-Long Chen
The effects of rapid, recent uplift of the Hengduan Mountains on evolution and diversification of young floristic lineages still remain unclear. Here, we investigate diversification of three closely related Saxifraga species with a distribution restricted to the Hengduan Mountains (HM) and southern Tibet, and comment on their taxonomy based on molecular evidence. Three chloroplast DNA fragments (rbcL, trnL-F, trnS-G) and the nuclear ribosomal DNA internal transcribed spacer (ITS) were employed to study genetic structure across 104 individuals from 12 populations of Saxifraga umbellulata, S. pasumensis, and S. banmaensis. Chloroplast DNA (cpDNA) phylogenies revealed two well supported clades, corresponding to S. umbellulata and S. pasumensis plus S. banmaensis. Topology of the ITS phylogeny was largely congruent with that generated from cpDNA haplotypes, but with minor conflicts which might be caused by incomplete lineage sorting. Analyses of molecular variance of both cpDNA and ITS datasets revealed that most variation was held between S. pasumensis s.l. (with S. banmaensis) and S. umbellulata (92.31% for cpDNA; 69.78% for ITS), suggesting a high degree of genetic divergence between them. Molecular clock analysis based on ITS dataset suggested that the divergence between S. pasumensis s.l. and S. umbellulata can be dated to 8.50 Ma, probably a result of vicariant allopatric diversification associated with the uplift events of the HM. Vicariance associated with HMuplifts may also have been responsible for infraspecific differentiation in S. pasumensis. In contrast, infraspecific differentiation in S. umbellulata was most likely triggered by Quaternary glaciations. The much lower levels of gene diversity within populations of S. pasumensis compared with S. umbellulata could have resulted from both range contractions and human collection on account of its putative medicinal properties. Combining evidence from morphology, geographical distributions and molecular phylogenetic data, we recommend that S. banmaensis should be treated as a synonymof S. pasumensis which in turn, and based on the same sources of evidence, should be treated as a separate species rather than as a variety of S. umbellulata.

Funding

This research was supported by CAS “Light of West China” Program, Youth Innovation Promotion Association, CAS (Grant No. 2016378) and National Natural Science Foundation of China (Grant No. 31110103911). RG is grateful to the High-end Foreign Experts Recruitment Program of the State Administration of Foreign Experts Affairs, P. R. China.

History

Citation

Frontiers in Plant Science, 2017, 8:1325

Author affiliation

/Organisation/COLLEGE OF LIFE SCIENCES/MBSP Non-Medical Departments/Department of Genetics

Version

  • VoR (Version of Record)

Published in

Frontiers in Plant Science

Publisher

Frontiers Media

eissn

1664-462X

Acceptance date

2017-07-14

Copyright date

2017

Available date

2018-01-09

Publisher version

https://www.frontiersin.org/articles/10.3389/fpls.2017.01325/full

Notes

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/article/10.3389/fpls.2017.01325/full#supplementary-material

Language

en

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