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Molecular phylogeny and biogeography of the narrow endemic Coelonema and affinitive Draba (Brassicaceae) based on two DNA regions
Authors:Shengyun Chen  Guili Wu  Shilong Chen  Jiawen Ren  Dahe Qin
Affiliation:1. State Key Laboratory of Cryospheric Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, the Chinese Academy of Sciences, Lanzhou 730000, China;2. Qilian Shan Station of Glaciology and Ecologic Environment, the Chinese Academy of Sciences, Yumen 735200, China;3. Key Laboratory of Arid and Grassland Ecology, Lanzhou University, Lanzhou 730000, China;4. Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, the Chinese Academy of Sciences, No. 59 Xiguan Avenue, Xining Qinghai, 810001, China
Abstract:To clarify the relationship between two genera, Draba and the narrow genus Coelonema, endemic to the QilianMountains of the northeastern Qinghai-Tibet Plateau, phylogenetic analyses were conducted using nuclear ribosomal DNA ITS, and the chloroplast DNA trnL, from Coelonema draboides and 30 species of Draba representing eight sections, including 25 species of Chinese Draba, seven of which were endemic to the study region. The results unambiguously support several previously published proposals to unite Coelonema with Draba and accommodate C. draboides in the latter genus on the basis of morphological re-examination. Our molecular data presented here also provide evidence that these two genera should be combined as a monophyletic group with high support. In addition, it is estimated that Draba may have originated about 1.36–2.71 Mya, with C. draboides diverging from Draba about 0.15–0.31 Mya, based on the molecular calibration of ITS datasets. The assumed speciation and rapid expansion of these two genera is likely to have occurred in the eastern edge of the QilianMountains area according to molecular phylogeny and estimated divergence times, which correspond well with the known geological and paleobotanical histories of the Qinghai-Tibet Plateau.
Keywords:Biogeography   Coelonema   Draba   ITS   Phylogeny   trnL
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