| Didymodon Hedw.is a large genus with wide distribution and many species in Pottiaceae Hampe.Its species show extremely rich morphological diversity.It is one of the most important groups to study the phylogenetic evolution of mosses.In recent years,foreign scholars have subdivided Didymodon into seven genera,but the definition of genus and the systematic status of some species are still controversial.The species of Didymodon have characteristics like high diversity,wide distribution and important ecological functions in China,and it’s a hot area of distribution.In this study,the species of Didymodon was selected as the research object.Through field investigation and a large number of literature inquiry,using the method of combining morphology and molecular systematics to explore the classification,geographic distribution and phylogenetic relationships of Didymodon s.lat.in China.The main research conclusions are as follows:1.According to statistics,47 species and 1 variety of Didymodon s.lat.are redivided into four genera in China,namely Didymodon s.str.(32 species and 1 variety),Geheebia(7 species),Husnotiella(6 species)and Trichostomopsis(2 species).2.The most critical taxonomic features of Didymodon s.lat.include: Leaf state when dry and moist,leaf apex,the shape of the ventral surface cells of costa above midleaf,the number of cell layers at the upper laminal margin cells,the structure of the lower middleaf costa(the number of layers of ventral stereids,the number of layers of guide cells),leaf margin recurved characteristic.3.Using the sequences of nuclear gene ITS and chloroplast gene(rps4,trn M-trn V),This study constructed a phylogenetic tree from the perspective of molecular systematics using Bayesian analysis and maximum likelihood method analysis.This study supports the idea of dividing Didymodon s.lat.of the world into seven genera.The genus Didymodon s.lat.in China is divided into four genera,and supports the status of Didymodon gaochienii as an independent species. |
