| Mongolian plateau, in the hinterland of Eurasian continent, includes Mongolia, southern Siberia of Russia and northern regions of China. The study chose Mongolia and Inner Mongolia of China, the main part of Mongolian Plateau (referred to as Mongolian Plateau). The study was on the basis of the previous collection and research, through the specimen collection, sorting, using the method of comprehensive analysis of morphological data and molecular data to explore the classification, geographic distribution and phylogenetic relationships of Didymodon sect. Didymodon in Mongolian Plateau. The main conclusions are as follows:1. According to statistics,17 species and 1 variety of Didymodon sect. Didymodon are reported in Mongolian Plateau, including 2 new species:D. innermongolicus and D. mongolicus:1 taxon is recorded new to Mongolia:D. rufidulus.10 species are found in both Mongolia and Inner Mongolia. China. D. australasiae, D. glaucus. D. mongolicus, D. subandreaeoides and D. rigidulus var. sublatus are onlv found in Monaolia. as well as D. baii. D. cordatus. D. ditrichoides and D. rivicola are only found in Inner Mongolia, China. D. anserinocapitatus, D. luridus and D. validus are excluded from Didymodon sect. Didymodon of the study area.2. Didymodon sect. Didymodon is distinguished from Didymodon sect. Fallaces by its not elongate, quadrate, short rectangular or subquadrate ventral surface cells of costa above midleaf. Some characters, such as leaf state when dry, leaf shape, leaf apex, margin, gammae, the number of layers of guide cells and the type of papillae, play an important role in distinguishing species under section.3. Molecular phylogenetic analysis based on chloroplast rps4 and nuclear ITS sequences suggested, rps4 sequences did not resolve the internal relationships as a result of lacking of effective sequence information sites. Bayesian analysis based on ITS sequences showed Didymodon include 2 taxa, one group consists of Didymodon sect. Fallaces, Didymodon sect. Vineales and Didymodon sect. Asteriscium, another group is mainly from Didymodon sect. Didymodon. According to morphological and molecular data, author suggest that Didymodon sect. Rufiduli and Fuscobryum are reduced to subsections of Didymodon sect. Didymodon.4. Molecular phylogenetic analysis revealed D. mongolicus shows a sister relationship to D. icmadophilus with high support (PP=0.98); D. innermonglicus is most closely related to D. tectorum and D. cordatus. which is also supported by morphological data. |
