Taxonomy And Phylogeny Of Rehmannia

There are about 6 species in Rehmannia, of which, Chinese traditional medicine R. glutinosa distributed from East Asia to Japan, all others are endemic to China. As worldwide studies emphasized on R. glutinosa but neglected other species, it leaves us many unsettled problems related to Rehmannia, such as, how to differentiate R. glutinosa from similar species, where is R. elata, and how about the phylogenetic development of the genus. This thesis is an exploration aimed to all those problems from the view of taxonomy and phylogeny.Start with specimen researches on Rehmannia geographic distribution and environmental adaptive traits both from herbaria and from field environments, detailed species data have been acquired, which provide ecological evidences for taxonomy. Next, morphological and anatomical studies performed on fruits, seeds, seedlings, root tubers, leaves, stems, flowers, pollens and placentas of Rehmannia, and many particular identifying characters and variations of each species acquired for the first time. By comparing fruit and seed morphology, pollen characters and placenta types with other genera, it shows that Rehmannia has some possible relationships with Gratiola, Digitalis, Paederota, Wulfenia, Picrorhiza, Mazus and Buddleja.To explore the relationship among the species of Rehmannia, cross-fertilization have been performed. The results indicate that R. glutinosa exhibits wider distances . from other species, whereas R. piasezkii and R. elata are among the closest species. Cytological observation brings out the first records on the same chromosome number 2n=28 of R. piasezkii, R. elata, R. henry and R. chingii, and suggested polyploid nature in R. glutinosa. Phytochemical analysis reveals existence of iridoid glycoside (catalpol and aucubin), with the most abundant catalpol content in root tubers of R. glutinosa.Internal transcribed spacer (ITS) sequences of all the Rehmannia species have been sequenced, among which, 5 sequences (R.glutinosa, DQ069312; R. chingii, DQ069313; R. solanifolia, DQ069314; R. etata, DQ069315; R. piasezkii, DQ069316 are accepted by Gene Bank of NCBI.Molecular phylogenetic analysis using ITS sequences from Rehmannia and other 39 related genera have been performed under PAUP* 4.0bl0 and Mrbayes 3.0b4.Three kind of consensus trees (Maximum Parsimony tree, Neighbor Joining tree and Bayesian Inference tree) show approximately similar branches with Rehmannia always a sister group of Buddleja and Oreosolen.For species within Rehmannia, phylogenetic analysis shows that it's a monophyletic group with 3 clades: clade 1, R. chingii and R. henryi; clade 2, R. elata and R. piasezkii; clade 3, R. glutinosa and R. solanifolia. Herein, the two species of clade 2 deserve to be considered one species because of the highest bootstrap percentages and morphological resemblance and their overlapping distribution, and clade 3 an advanced group considering its polyploid nature.For systematic position of Rehmannia in Lamiales, it shows that Rehmannia may be considered a member of Scrophulariaceae (sensu stricto), be close to tribe Gratiolieae and Rhinantheae of Veronicaceae, be far from Gesneriaceae and tribe Digitalieae of Veronicaceae, with supports from phylogenetic analysis, phytochemical studies, morphological and anatomical observes.Lastly, a revision of Rehmannia taxonomy achieved: (1) a new synonym of Rehmannia piasezkii Maxim.—Rehmannia elata N. E. Brown (syn. nov.), (2) an amended description of the genus and species, (3) a new key for species, and (4) a detailed feature collection for identifying Chinese traditional medicine R. glutinosa.