| Climate change is the primary driving force of changes in species distribution patterns,and species migration will directly affect ecosystem services.Didymodon Hedw.is a prototypical xerophytic moss and the predominant ground cover in the delicate ecological milieu of cold and arid regions.With the widespread application of molecular technology and spatial distribution model and the extensive development of bryophyte investigation,the species inventory and geographical distribution information of Didymodon in China has been further updated and enhanced.Moreover,previous studies have simulated the future distribution patterns and migratory behavior of Didymodon in localized regions of China,revealing its potential as an effective indicator for climate change and habitat fragmentation.However,to date,there is a lack of comprehensive national-scale reports on the species diversity of Didymodon and no deep study of the distribution pattern and variation of the genus’species has been documented.Therefore,on the basis of extensive field investigation,data collection and collation,combined with model specimen collection,this study used a combination of classical morphological taxonomy and molecular phylogeny to study the species diversity of the Didymodon in China;The simulation of spatial distribution patterns is used to compare the characteristics and differences among different Didymodon species and explore their relationship with topographic and climatic factors;A high-precision distribution model is employed to predict the distribution patterns and migration routes of Didymodon species under future climate conditions,thereby revealing the impact of climate change on typical Chinese Didymodon species distributions,and the species with indicative potential for climate change were screened out.The main results of this study are as follows:（1）On the basis field survey and the borrowing of resources from the main herbarium collection in China,combined with classical morphological taxonomy and molecular phylogeny,48 species（including 1 variety）of Didymodon in China were identified,including3 new species of Didymodon from Didymodon changbaiensis C.Feng,J.Kou,H.-X.Xiao et T.-T.Wu sp.nov.,D.manhanensis C.Feng et J.Kou sp.nov.and D.sinicus C.Feng et J.Kou.sp.nov..And,the leaf shape and tip shape of the plant,the number of cell layers on the ventral side of the upper part of the middle rib of the leaf,the number of layers of the abdominal thick-walled cell belt in the middle and lower part of the middle rib of the leaf,the number of guide cell layers,the number and morphology of cell layers on the upper edge of the leaf,and whether the leaf edge is curled can effectively distinguish most of the species of Didymodon in China.（2）The MaxEnt model and ArcGIS software were employed to simulate and visualize the potential geographical distribution of 22 Didymodon species in China.The results showed that most of the potential geographical distribution centers of the species were concentrated in the Qinghai-Tibet Plateau and the Hengduan Mountains in southwestern China,and the probability of the distribution of the species in the extremely humid areas was extremely low.Furthermore,the potential geographic distribution areas of D.tibeticus J.Kou,X.-M.Shao et C.Feng,D.erosodenticulatus（Müll.Hal.）K.Saito,and D.mesopapillosus J.Kou,X.-M.Shao et C.Feng in China are narrow and concentrated.Moreover,the highly suitable areas only account for 0.96%,1.10%,and 1.12%of China’s national land area.（3）Altitude is the primary environmental factor influencing the simulation of the potential geographical distribution of most Didymodon species in China,and it also serves as the main limiting factor for the geographical distribution and distribution range of most Didymodon species in China.Temperature variables contribute more significantly to the formation of most Didymodon species distribution patterns compared to precipitation variables.Among them,the contribution of isothermality（Bio3）and temperature seasonality（Bio4）to the species distribution simulation of Didymodon ranks second only to elevation.The impacts of precipitation on the distribution of D.johansenii（R.S.Williams）H.A.Crum,D.giganteus（Funck）Jur.,D.hedysariformis Otnyukov,and D.gaochenii B.C.Tan et Y.Jia were found to be more pronounced compared to elevation and temperature,suggesting a higher sensitivity of these species towards precipitation.The contribution rate of each environmental factor to the simulation of the subgenus Didymodon species showed a high similarity,suggesting that the relationship between the distribution of these species and the key environmental variables may be related to their phylogenetic position.The response relationship is similar between the distribution probability of most Didymodon species and environmental variables.The distribution probability of Didymodon species is generally higher in the high mountainous areas with an altitude of about 4000 m in China,and the optimal growth environment conditions of most Didymodon species are similar,and there may be niche overlap.The suitable environment threshold of D.hedysariformis Otnyukov,D.gaochenii B.C.Tan et Y.Jia,and D.johansenii（R.S.Williams）H.A.Crum exhibited robust adaptability to temperature variables while displaying high sensitivity to precipitation variables.（4）Through the simulation of the species distribution patterns under the future climate background,it is found that the distribution of Didymodon species in China is relatively stable,and in the future,it will still exhibit a concentrated distribution pattern dominated by the Qinghai-Tibet Plateau and the Hengduan Mountains.Compared with the potential distribution area of current species,the distribution range of most species of bryophytes in the suitable habitat in China will generally expanding in the future,and increase with the increase of CO2emission concentration.However,the distribution area of D.asperifolius（Mitt.）H.A.Crum,Steere et L.E.Anderson,D.perobtusus Broth.,D.tibeticus J.Kou,J.A.Jiménez,X.-M.Shao et C.Feng,D.mesopapillosus J.Kou,X.-M.Shao et C.Feng,D.acutus（Brid.）K.Saito and D.icmadophilus（Schimp.et C.Muell.）K.Saito,is narrow and concentrated and will be reduced under different CO2 emission concentrations in the future,while the potential geographical distribution centers of most species of Didymodon will show a trend of migration from east to west.In conclusion,this study systematically summarized the species diversity information of bryophytes in China,and provided basic data support for the ecological and physiological research of bryophytes in China.In addition,using spatial and climate data for the first time,this study discussed the distribution pattern of bryophytes in China under the background of climate change and its dynamic change trend with the passage of time and the increase of CO2emission concentration,and analyzed the role of key environmental factors in the formation of the distribution pattern of Bryophytes in China,which was helpful to understand the adaptability and response ability of species to climate change. |
