Phylogeographic Study Of Riparian Plant Ceratostigma Minus On The Qinghai-Tibet Plateau And In Adjacent Region

Ceratostigma minus in Genus Ceratostigma Bunge of Plumbaginaceae,is endemic to China.Ceratostigma minus in the Dry-hot valley of the Yarlu Zangbo River,the Nu River and the Yangtze River upstream(including a tributary of Yalong River,Dadu River,Minjiang River,Yuanjiang River,etc.)has a wide geographical range from western Sichuan to eastern Tibet and from south Central Yunnan to Wenxian county of Gansu province.In order to test its genetic differentiation,geographic origin and expansion as well as the effect of historical events during plant speciation and evolution,molecular systematics,phylogeography and population genetics of Ceratostigma minus based on DNA sequences were studied.Also,the possible relationship between its phylogeographic structure,distribution pattern and the drainage pattern of the major rivers in its species range was discussed.A total of 31 haplotypes were detected in 741 Ceratostigma minus individual plants from 45 populations by using two cpDNA fragements,trn L-F and pet L-psbE.C.minus showed high genetic diversity and high genetic differentiation.The haplotype diversity(Hd)was 0.825 and the total genetic diversity(HT)is 0.847.The coefficient of gene differentiation(GST)is 0.920.AMOVA analysis showed that most of the variation resided in among populations(0.847).The phylogenic relationship among haplotypes of C.minus and their divergence time indicated that the distribution of C.minus was realated to the geographic distribution of major rivers,which might relate to the capture of the ancient rivers.The nested clade analysis showed that the geographical structure of C.minus was due to allopatric fragmention and restricted gene flow with isolation by distance,which supported the result of the intraspecific evolutionary tree.The mismatch analysis and neutral test indicated that C.minus did not undergo any rapid population expansion.