On Genetic Diversity And Phytogeography Of Macromitrium Gymnostomum

Macromitrium gymnostomum Sull.& Lesq.widely distributed in subtropical and warm temperate areas,with a high morphological variation.To understand the status of genetic diversity and morphological variation,morphological differentiation of geographical populations,and to clarify whether its morphological variations are affected by genetic background or geographical origin,we conducted an integrated study including morphological variation,genetic diversity,and molecular biogeography by using 140 samples of M.gymnostomum from 25 geographical locations in Zhejiang,Guangxi,Fujian,Guizhou,Taiwan provinces.According to the present and future climatic conditions,we predicted the potential geographical distribution region of the species and its possible changes.The main results are as follows:1.32 morphological traits of 140 samples from 25 geographical populations of M.gymnostomum were determined.According to the variation coefficient,we found that the characters with higher morphological variations included the leaf base width,leaf lower cells width,leaf upper middle cell length,leaf base length,and leaf lower length.Meanwhile,other characters show low morphological variation,which included costa length,folds number of branch leaves,basal cell width,leaf apex angle,the revolution number of leaf.2.Among 140 samples of M.gymnostomum,93 samples have capsules,accounting for 66.43% of the total samples.The proportion of the samples with capsules varied among different geographical populations.Capsules were often absent in the samples collected from island environments,while present in 95% samples collected from Fujian,Guizhou and Guangxi.3.Based on 32 morphological traits of branch leaves,the 140 samples could be clustered into eight groups.Except revolution number of branch leaves(P = 0.949),other 31 traits were all significantly different among eight groups(P < 0.01),which reveal a good division of the 140 samples by using Cluster Analysis.Based Principal Component Analysis on the morphological traits,140 samples were roughly divided into two groups.The samples in Group I were collected from Libo and Jiangkou(in Guizhou),and some from Guangxi,Taiwan and Fujian;while those in Group II were mainly from Zhoushan Islands and the eastern coastal mountains.6.According to the sequences of nr ITS of the 140 samples,21 haplotypes were found.In the species level,haplotype diversity(h)is 0.688,nucleotide diversity(?)is 4.21×10-3.H1 was a widespread haplotype,found in 16 samples and 8 geographic groups.H2 was the second large haplotype,found in 7 samples and 5 geographic groups.H3 was in the inland region of Zhejiang Province(not including Zhoushan Archipelago).H4 was found in the samples collected from Nantou(NT),Longwantan(LW),Maolan(ML).H5 was found in the samples from Liangyuan(LY),Maolan(ML),Jiangkou(JK).Other haplotypes were all found from single geographical unit.Our analyses showed that H1,H2 and H3 were ancient haplotypes at internal of haplotype network.The haplotype network revealed the pattern of speciation is like two ancient haplotypes(H1,H2)evolved new haplotypes respectively.Other haplotypes evolved from these two haplotypes.According to the distribution pattern of haplotypes in 25 populations of M.gymnostoumum,we found a molecular geographical relationships among these populations,with relatively close relationships among the eatern inland areas and costal islands of Zhejiang,and among some areas in southwestern China.4.The correlation coefficients among morphological,genetic and geographic distances among the 140 samples were calculated.We found that the morphological variation of M.gymnostomum was influenced by geographic origin(P < 0.01),but there was a lack of genetic background based on ITS2.The possible reasons maybe that morphological variation of M.gymnostomum were mainly resulted from climate factors.However,the morphological variations had no genetic background,being geographically plastic.5.Based on 150 occurrence data of M.gymnostomum,and 38 environmental variables,the potential geographical region of M.gymnostomum was predicted by using a maximum entropy algorithm modeling program(Max Ent).The environmental variables included temperature,rainfall,sunshine,evaporation,etc.In view of present climate,sunshine and vegetation conditions,we found that the potential geographical regions of M.gymnostomum covered the Southeastern China(Zhejiang,Anhui and Jiangxi province),Southern China(Fujian,Taiwan and Guangdong and Guangxi province),and Southwestern China(Guizhou,Chongqing,eastern Sichuan and the eastern border of Yunnan).The distribution of M.gymnostonmum were mainly influenced by nine environmental variables,which included Annual Mean Temperature(contribution 26.5%),water evaporation in August(16.7%),mixed forests(14.2%),mean temperature of the coldest quarter(12.7%),solar radiation in December(9.7%),solar radiation in March(8%),solar radiation in May(2.9%),max temperature of the warmest month(2.8%),mean Temperature of the driest quarter(1.8%).We also predicted the potential distribution regions of M.gymnostomum based seven bioclimate variables under current,2050 and 2070 climate conditions.The integrated habitat suitability indexes of M.gymnostomum in the whole country was 0.980(current),0.937(2050)and 0.908(2070),which reveal that the distribution regions of M.gymnostoumum in China will become narrower under warming climates.Compared with the current distribution range of the species,those in 2050 or 2070 will decrease,or even disappear in Anhui,northern Zhejiang,southern Fujian,Guangdong,Guangxi,Hunan,southern Hubei.