Landscape Genetics Of Three Cymbidium Species From The Mountain Regions Of Jiangxi Province

Cymbidium are one of the most important ornamental plants of Orchidaceae.Most of them are rare and endangered plants,and they are all included in the protection scope of the Convention on International Trade in Endangered Species of Wild Fauna and Flora(CITES).The genus is mainly distributed in the subtropical and tropical Asia and Austrialia.Cymbidium plants spread over various mountain ranges.It is an ideal species to identify geographical isolation and landscape isolation.Little is known about the geographical distribution patterns of Cymbidium species to date.In this study,we combined genetic data(cpDNA ITS,and ISSR markers)and geospatial data(climate and geographic location)with landscape genetics to infer the historical migration corridors and glacier refuge of the three Cymbidium species(Cymbidium ensifolium,Cymbidium kanran,and Cymbidium faberi)in the Mountain regions of Jiangxi,a province known for its mountainous landscape in southeast China.The main results are as follows.First,based on species distribution models(SDMs)of geospatial and climate data,we studied the distribution of the suitable areas of the three species in China.Our results showed that the distribution pattern of these speciesin the paleoclimate period was consistent with the current one,indicating that there were multiple refugia in the mountain areas of China.In addition,the suitable habitats of C.ensifolium,C.kanran and C.faberi are mainly distributed in south China.The suitable habitats of C.ensifolium and C.faberi are found primarily in Jiangxi,Fujian,Guangdong,Taiwan.Compared with C.ensifolium and C.kanran,suitable habitats for C.faberi are more widely distributed in China,extending to Sichuan,Yunnan,Zhejiang provinces and Chongqing.Under the scenarios of climate change,species distribution model prediction of the potential changes of C.ensifolium,C.kanran and C.faberi in China have been made.We found that the suitable habitats for C.ensifolium and C.kanran showed a trend of range contraction,while C.faberi showed range expansion under a warming climate.Second,we studied the population structure of the three Cymbidium species in the mountain regions of Jiangxi Province using cpDNA,ITS,and ISSR markers.Cymbidium ensifolium can be divided into 3 groups.Barrier analysis identified three major barriers among the seventeen populations.The first barrier was located between the Luoxiao mountains and Wuyi mountains.Optimal group division The optimal K value for C.faberi populations was also 3.Barrier analysis determined three major barriers.The first barrier was located between the Luoxiao mountains and Jiuling mountains.Unlike C.ensifolium and C.faberi,and the optimal division value of C.kanran is 2.Barrier analysis confirmed the first barrier was located between clusterⅠand clusterⅡ.From the overall genetic structure map,the most likely genetic structure group(K)of three plant populations was inferred based on ISSR data.However,there was also mixing among the populations,suggsting that dispersal and gene flow were occurred among these mountains.Third,combing genetic data and species distribution model,we simulated potential dispersal route in three time periods using the least cost path method.The main results are as follows.There are two dispersal corridors for C.ensifolium:Luoxiao mountains-Dayu ling mountains,and Jiulianshan mountains-Wuyi mountains.There are two migration corridors of C.kanran:Jiuling mountains-Yushan mountains-Wuyi mountains and Jiulian mountains-Wuyi mountains.There are two dispersal corridors for C.faberi:the Jiuling mountains,and Jiuling mountains-Yushan mountains-Wuyi mountains.In the future,compared with the other two corridors,the connectivity of the new migration corridor,Jiuling mountains-Huaiyu mountains will be enhanced.From the simulation results of the migration corridor,the mountains acted as a bridge,promoting gene flow between the eastern and western populations.Due to the fluctuation of quaternary climate,the habitats and migration corridors are often occupied by warm temperate evergreen forests,which may lead to the fragmentation of species habitats and aggravated the differentiation of eastern and western populations.Eventually,the population retreated to isolated mountain refugia,forming the current geographic pattern.