A Systematic Study Of The Rhodiola Sect.Trifida Group (Rhodiola Sect.Trifida)

Species is the basic unit of biodiversity research and conservation practice.How to delimit species accurately has always been the core issue of systematic research.In reecent years,with the united species concept,some authors tried to integrate multiple data,including morphological,different genetic markers and niche differentiation,and combine the evolutionary history to delimit species in complex groups,to provide a scientific and rational species delimitation of these groups.The Qinghai-Tibetan Plateau(QTP)and Hengduan mountains comprised the world's highest biodiversity hotspots.Studies have demonstrated that extensive uplift of QTP has triggered entensive diversification of some lineages.Species delimination in such lineages is often problematic.Our study focuses on Rhodiola Sect.Trifida(Frod.)S.H.Fu(Crassulaceae),which is endemic to the QTP and its adjacemt area.Although previous molecular phylogenetic study supported its monophyly,species dilimination in the section has been under dispute for a long time due to the abundant phenotypic variation and the diversity of habitats in the group.Based on extensive population sampling(590 individuals of 46 population),this stuy firstly investigated evolutionary history of this group using phylogeographic pipeline,and then integrated multiple sourse data,including morphological,different genetic markers and niche differentiation to get a better species delimination.The main results and conclusions are as follows:1.The evolution history of Rhodiola sect.TrifidaI here conducted a evolutionart history study using sequence of three chloroplast(trnL-F,psbA-trnH,trnS-G)and internal transcribed spacers in this group,the results showed that:1)the origin of major clades of sect.Trifida were in accordance with the last phase of QTP upflits,indicating that uplift of QTP has triggered diversification and origin of this group;2)a high frequency and an even distribution of private haplotypes in both plastid and ITS datasets throughout the distribution of sect.Trifida were detected.The ecological nich modeling results showed that there were suitable habitats on the QTP platform and Hengduan mountain during LGM.All those results found that multiple microrefugia existed on QTP platform and Hengduan mountain,supporting the hypothesis that species with similar distribution and inhabiting the same community had similar response to the Quaternary climatic oscillations.2.Species delimination of Rhodiola sect.TrifidaBased on the study of evolutionary history,this study combined multiple lines of evidence including morphological,molecular and ecological modeling for redefine the species delimination of Rhodiola sect.Ttrifda.Based on 46 population(7 morphology species),I firstly measured 14 morphological traits and conducted clustering analysis,and then combined 6 molecular markers(including two nuclear genes and the combination of the three segments of chloroplast and a ribosome ITS sequence)using Bayesian species definition method based on BP&P,finally implemented ecological niche modeling to redefine species boundaries of this group,the results showed that:1)R.liciae and R.sinuata has diverged from other species of sect.Trifida by morphology,molecular and ecology niche;reciprocal monophyly for R.liciae was achieved in the cpDNA data,and in the rpb2 data set;based on all BP&P results they were sister to other species of sect.Trifida;ecological nich analysis showed distinctness with other species.2)this analyses support merging R.chrysanthemifolia,R.ovatisepala,R.sexifolia and R.sacra into R.chrysanthemifolia:whether single gene tree or multispecies coalescent model phylogeny showed that those four morphology species has no genetic divergency;as for clustering analysis of morphological traits they were intermingled together;ecological modeling analysis also showed that distribution areas of the four species are very similar with rach other.3)The species status of R.alterna still needs to be further explored.This study inferred the evolutionary history and species delimination of Rhodiola sect.Trifida based on mulitiple evidence.The study provided further evidence that distribution pattern of species endemic to the QTP area has been affected by both complex geological heterogeneity and climatic oscillations in the Quaternary.Also,I used an intergratuve taxonomic method to revise species limits in Rhodiola sect.Trifida.This study provide evidence for the formation process and mechanism of biodiversity in QTP.At the same time,these results suggest that in the complex groups,using intergrative species delimination method can not only solve the dispute for a long time,but also can deepen our understanding for species differentiation and speciation process and mechanisms.