Phylogeography Of Rehmannia (Scrophulariaceae)

Rehmannia for perennial herbaceous plants,belonging to Scrophulariaceae,widely distributed in the central,eastern and northern China.China flora records about 6 species.Beside of R.glutinosa,traditional Chinese medicine,which reachs east Asia-Japan,the others are endemic plants in our country.Recent study demonstrates that Relmannia is merged into five species.For a long time,the medicinal properties and component analyes of R glutinosa are the focus of study.However,Little is known about the dynamic change with respect to geographic distribution and the formation and evolution history of Rehmannia.Therefore,a total of 51 populations and 576 specimens were collected across the entire Rehmannia distribution area.In order to effectively reveal the evolution history and the origin,distinctly clarify impacts of quaternary glacial climate fluctuations on change of distribution distribution and speculate glacial refuge and the centre of the diversity of Rehmaannia,three chloroplast genetic non-coding regions (trnL-trnF,trnM-trnV,trnS-trnG) and ribosome transcribed spacer ITS were sequenced cross all the samples for phylogenetic analysis of Rehmannia.The main conclusions are listed below:(1)Based on the cpDNA sequence analyses,the phylogenetic tree strongly supports the monophy of Rehmannia(100%).R chingii as the first diverged species located at the bpoase of phylogenetic tree,followed by R henryi,R piasezkii,R glutinosa and R solanifolia constituting a sister groups with rapidly radiation.(2)Further analysis based on nrlTS region,the median-joining network identifies shared generaltypes between R chingii and R henryi.The phylogenetic tree clarifies that R henryi nested in R chingii,ocuppied the same genetic branch joinly.Our results infer that species divergence already took place,sometimes followed by secondary contact hybridization and introgression between divergent inter-specific taxa,resulting in ITS evolutionary incompletely.(3)The genetic diversity patterns based on cpDNA and nrDNA sequence variation revealed a strong degree of genetic differentiation among Rehmannia.The firstly species differentiation occurred in the early Pleistocene,that is 2.45mya using BEAST.Analysis on population,we estimated Rehmannia underwent population expansion after 0.12Ma,orresponding to the occurrence of Quaternary climatic oscillations.(4)Based on morphology evidence,chloroplast and ITS sequence analysis showed that R solanifolia alwaylys contained by R glutinosa.Thus,From morphology and the specimen observation, we support R glutinosa and R solanifolia should be the same species with two species similar morphology and overlaping geographic area.(5)Based geographic distribution pattern and geneic diversity analyes,shennongjia-wushan area may be centers of genetic diversity and potential refuges for Rehmannia.Shennongjia mountain and east Mongolia become possible glacial refugias for R glutinosa,that is Tianmu mountains to R. chingii.These findings point to the importance of geological and climatic changes during the Pleistocene as causes of interspeciflc diversification and range shifts of Rehmannia.