| The application of molecular data has greatly changed the classification system of Saussurea.Twenty sections from six subgenera identified based on the morphological characteristics were found to show some classification errors.One subgenus and three sections belonging to another subgenus in these twenty sections representing six subgenera were determined as the single genus through phylogenetic studies.Meanwhile,the research results showed that most of the remaining sixteen sections from five subgenera were not natural groups.The previous studies possessed some limitations that several individuals,often less than five samples,were sampled for systematics studies,especially subg.Theodorea.The sampled individuals were too few to represent the actual genetic diversity of these sections or subgenera.Subg.Theodorea consists of twenty species mainly distributed in the Eurasian continent of North Temperate Zone.Most species exist in high altitude areas of northern China containing recorded seventeen species including two widespread species and eleven endemic species in China.The subgenus species have the private structure-the tablet on the top of total tablets,namely purple,membranous and enlarged appendages.However,there are significant differences in the morphology of tablets among species in subg.Theodorea.According to two mainly type of the tablets,Lipschitz devided subg.Theodorea into two groups,subg.Theodorea sect.echenais and subg.Theodorea sect.spanioptilon.Because of the significant differences of two types of the tablets and one of the two types differ from species in other subgenera on the aspect of the appendage color,it is worthy to be investigated whether the two groups came from the same ancestor.In addition,the morphological differences between the two species are great,while the distributional ranges of the most endemic species are small and the differences between species are not significant.Therefore,the taxonomic of these species are still to be verified.To solve the questions above,we conducted a large number of field investigation containing the distribution ranges of the subgenus.We collected specimens and plants from 58 populations representing 10 species in subg.Theodorea sect.echenais,1 species in subg.Theodorea sect.Spanioptilon,48 populations representing 7 species in subg.Saussurea sect.laguranthera and 5populations reprsenting 1 species in subg.Saussurea sect.Acaules.The tested four gene regions containing three chloroplast genes(psb A-trn H,trnK and matK)and one nuclear gene(ITS)were amplified and sequenced.The sequencing results and those of 26 were used to construct two group data.One group data contained ITS sequences,with a length of 680 bp,247 variable sites and 151 informative sites.The other contained three chloroplast genes,with a length of 2283 bp,135 variable sites and 75 informative sites.Bayes trees were constructed based on the two group data.The results showed that Saussurea DC.could been classified into two large branches.One branch consisted of 11 species in subg.Theodorea sect.echenais,6 species in subg.Saussurea sect.laguranthera and 1 species in subg.Saussurea sect.acaules.While,the other branch consisted of the remaining species in subg.Saussurea sect.laguranthera and subg.Saussurea sect.acaules and representative species in other subgenera.Whereas,the former was further clustered into two branches and the branch results of three chloroplast genes were continent with those of ITS.Synthetically considering various data including chromosome number,morphological characteristics,geographical distribution and other microscopic traits,we got some results as the followings:1.Subg.Theodorea should be classified and determined.The results both showed that species in subg.Theodorea sect.echenais and some species in subg.Saussurea sect.laguranthera and subg.Saussurea sect.acaules.could cluster into a single pedigree branch.Meanwhile,the species with tablets showed affinity relationships with the species without tablets supporting that subg.Theodorea should been redefined and some species in subg.Saussurea sect.laguranthera and subg.Saussurea sect.acaules should be transferred to the subgen.Theodorea.These species were all perennial herbs with some similar morphological characteristics rarely found in other subgenera.We speculated that part of the features could be the synapomorphy of the subgenus.Whereas,subg.Theodorea might be the result of multiple origins within the subgenus.2.Redefined subg.Theodorea clustered into two branches based on the phylogenetic analysis of ITS sequences.One branch consisted of 9 species in subg.Theodorea sect.echenais and 5species in subg.Saussurea sect.laguranthera.While,the other branch consisted of 1 species in subg.Theodorea sect.spanioptilon,3 species in subg.Saussurea Sect.laguranthera and 1 spcies subg.Saussurea sect.acaules.The two branches both showed the same posterior probability of100%.However,the analysis results of three chloroplast genes,together with chromosome number and some morphological characteristics,were not consistent with those of ITS.Therefore,the classification of subg.Theodorea should be further studied.Otherwise,the results also showed that the top shapes of external total tablets including three types(bone-like,membranous and acuminate),often used to compile the retrieval table,could be the result of multiple origins withinthe subgenus and the species with similar morphological characteristics do not necessarily have a closer relationship.3.Saussurea japonica and Saussurea amara have a widespread distribution ranges.Different individuals within the species have significant differences on tha aspect of morphological characteristics.They both have been published as multiple species and currently have been merged as two variants.The study investigated 27 individuals from 11 populations of the two species.The results showed that significant differences were found on the morphological characteristics and genetic diversity of these populations.The mean value of genetic distances within species in Saussurea japonica was 0.00065,while mean value of genetic distances within species in was0.0033.However,the private populations of two species clustered into one single branch and sub-branches consistent with the morphological variation were not found supporting the current classification of two species.No less than three individuals from other species were analyzed.The results showed that most species clustered into one single branch.However,three species,including Saussurea salsa,Saussurea davurica and Saussurea laionowii,and two species,including Saussurea pinnatidentata and Saussurea japonica,were composed of two multiple divergent branches.Otherwise,the morphological characteristics of these species were relatively similar.Therefore,we speculated that hybridization events or late differentiation might make a contribution to the situation. |
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