Phylogenetic Study On Racomitrium Of China

In this study, gene sequencing methods combined with traditional morphologicalmethods were used to study phylogeny of Racomitrium in China.24speciesdistirbuted in China were studied and the samples were collected from North Ameirca，Asia, Europe and most of them rfom China. For molecular studies, three chloroplastgenes (trnL, trnG, psbT) plus one nuclear ribosomal RNA gene (ITS2) were used.Atfer receiving sequences, PAUP，Phyde，MacClade，MrBayes and other sotfwareswere used for systematic analysis. The morphological systematic trees and molecularphylogenetic trees reflect the evolutionary relationships between the various speciesare basically uniform. The basic results are as following:1)The phylogenetic tree shows that the involved species of Racomitrium in theresearch performed a single Department of Genetics, with a95%bootstrap supportand the posterior probability was0.95. Therefore，the traditional concept ofRacomitrium should be retained as a genus. The trees don’t support the viewpoint ofBednarek-Ochyra and Ochyra (2003) that regarded Racomitrium as a subfamily ofGirmmiaceae and divided into four genera (Bucklandiella, Niphotrichum，Racomitrium and Codriophorus).2)The molecular results of this study support the categorization that dividedRacomitrium into four groups which Bednarek-Ochyra and Ochyra proposed based ontraditional morphological characteristics. Further, suggest to arranging them as foursubgenera including subg. Racomitrium，subg. Niphotrichum, subg. Codriophorus andsubg. Bucklandiella.3)However，in the systematic trees based on molecular data, all samples of R.aciclure keep off from other species and flock together. The morphological characteirstics are also special, the leaf tips are obtuse and distinct from other speciesin this study. So the species is recommended to be treated as a single subgenus.4)The early researchers had different viewpoints about the position of R.sudeticum. In this study, molecular evidences support to leave it in the genus ofRacomitrium and affiliate to the group of Bucklandiella. However, further study isnecessary because of the samples are scarce.5)During the process of creating phylogenetic trees based on gene fragments,comparing with each other，the resolution of the sequences of trnL is the best，thenITS2，followed by trnG, the effect ofpsbT is the worst among all four genes.6)For the3methods of creating the phylogenetic trees, including MaximumParsimony, Maximum Likelihood and Bayesian, the topologies are basically the sameand the resolutions are also roughly equal. But the phylogenetic trees established byBayesian method usually with a higher support rate, followed by the MaximumLikelihood method. Both are all superior to the Maximum Parsimony method.