| Taxus chinensis var.mairei(T.mairei),an endemic species in China belonging to ancient 3rd century relic species,has been listed as the first-class protective wild plants of China.Nanling Mountain,a large number of ancient relic plants existed in and the distribution centers and "shelters" of ancient conifers,is the southem boundary for the distribution of T.mairei.Nanling belongs to rarely transverse mountainsin China and consists of numerous discontinuous mountains.A lot of basins,valleys and rivers were distributed forming the small climate and diverse terrain environment,which leading to the habitat diversity and genetic diversity for T.mairei populations.In this study,the climatic factors in 23 natural distribution populations of T.mairei were obtained through the interpolation and correction by using regression model and Ordinary Kriging method based on ArcGIS.Combining with morphological characteristics,cellular anatomy and microsatellite(EST-SSRs)marker technology,the comprehensive research about natural geographical distribution,habitat climate characteristics and genetic variation were carried out for T.mairei on Nanling.The results will provide scientific basis for the classification and protection of T.mairei.The main results were as follows:(1)The annual mean temperature(AMT)of 23 T.mairei populations in Nanling distribution area varied from 12.175 to 18.263 ? the optimum temperature range from 14.972 to 18.492? with an average of 16.732?.The warmth index(WI)varied from 86.381 to 160.420? per month,the optimum temperature range of 118.811?162.353? permonth with a mean of 140.582? per month;The cold index(CI)varied from-4.262 to-1.196? per month,the optimum temperature range from-2.885 to-1.169? per month with an average of-2.027? per month.The Xu Wenduo's humidity index varied from 9.264 to 13.687mm·(?·month)-1,the optimum temperature range of 9.689?11.909mm·(?·month)-1 with a mean of 10.799 mm·(?·month)-1;The potential evapotranspiration rate(PER)was 0.159?0.939 with optimum range varied from 0.416 to 0.906 with an average of 0.661;the annual mean rainfall(AMP)varied from 1147.996 to 1591.286mm with a mean of 1452.643mm.The annual average relative humidity were 77.473?82.347%with an average of 79.128%;the sunshine duration(SD)varied from 1194.318 to 1785.059h with a mean of 1509.458h.According to Penman's vegetation-climate classification system,Holdridge life zone classification system and Kira's temperature index classification,T.mairei are the tree species in subtropical humid forest life zone,with warm temperate and humidity climate type.The principal component analysis(PCA)showed that extreme temperature,humidity factor,geographical factor that played dominant roles in the geographical distribution of T.mairei.Clustering analysis showed that the populations of T.mairei were divided into three groups,the high altitude of Sangzhi and Rongshui were clustered into one group;The second group are in the East,including Guangdong,Jiangxi,Fujian,Zhejiang,Guangxi Rongshui,Hunan Youxian;The third group are in the west,including the west of Hunan Guangxi Ziyuan and Longsheng,Guizhou Taijiang.There was no significant difference between the groups in East and West areas although the most of climatic factors in eastern area was higher than that of the western area and high altitudes.The correlation analysis of geospatial and climatic factor showed that a negative correlation between the majority of climate factors and the latitude while longitude,aridity indexand sunshine duration were extremely negative correlation(P<0.01).There was a significant or highly significant correlation between the altitudinal and most of the climatic factors.The distribution of each group mainly ranged firom 500 to 1000m.(2)The phenotypic genetic diversity of the three populations,Sangzhi,Youxian,Rongshui,which represents the upper and lower limit of altitude distribution,were low.The coefficient of variation of leaf length and leaf width were less than or equal to 15%.The leaf length and leaf width showed that Sangzhipopulation>Youxian population>Rongshuipopulation.The leaf length and width of the Rongshui population had extremely significant differences with those of the Sangzhi and Youxian groups,while Sangzhi and Youxian groups did not reach a significant level(P<0.01).There was no significant difference in the ration of leaf and widthlength between the three populations.The correlations of leaf length,width,aspect ratio and latitude,longtitudewere not significant.A significant negative correlation were shown between leaf length and aspect ratio and altitude gradient,while leaf width and altitude gradient were not significant.The leaf length,leaf width and leaf aspect ratio of the three altitudinal gradients,low elevation(1500?1600m),middle elevation(1700?1800m)and high altitude(1900?2000m),had significantly correlation with the altitudinal gradient.The leaf length and width at low altitude were significantly larger than those of medium and high altitude,while medium and high altitudewere not significantly.The leaf anatomical structure of Guangxi Rongshui,Youxian and Sangzhi of Hunan and Henan Lushan showed the common features of low light tolerance,resistance to cold and humidity;But the similarity between T.mairei in Rongshui and T.chinensis in Lushan was higher than that in Sangzhi and Youxian.Therefore,the Taxus chinensis var.mairei in Rongshui should be further identified.The shape of seeds from Sangzhi population were dominated by two longitudinal ridges or three longitudinal ridges,while four longitudinal ridges existed in Youxian population.The number of lateral leaves and leaves of Sangzhi population were higher than those of the Youxian populations in synchronization.(3)13 micro satellite loci were selected to analyses nine representative populations in Nanling with 217 individuals,the results demonstrated that genetic diversity ofT.maireiwere at a moderate level(He=0.459),and the degree of inbred was higher(Fis =0.249).Significant genetic differentiation existed among populations(Fst=0.251,P<0.01)and the gene flow(Nm)was 0.746<1.There was a clustering tendency by geographical distance and climatic factors among population in which Rongshui and sangzhi population have far relationship with other populations.As the vertical distribution,the average number of alleles(Na)is 4.02,the average heterozygosity(He)is 0.48,and the average Shannon index(I)is 0.92 for the 4 altitude gradient population in Badagongshan,indicating that T.mairei have moderate genetic diversity.The genetic diversity of low-altitude were higher than that of high-altitude population,there was significant genetic differentiation and genetic distance between Bd4 population and other low-elevation populations.Thegene flow within 4 altitude gradient populations were sufficient.The obvious climatic differences in high altitude areas may be the main cause of genetic differentiation among populations.On the large scale,the Shannon's information index(I)and the expected heterozygosity(He)of the 9 populations weresignificantlynegativelycorrelated with the altitude(P<0.05),and the correlation with the longitude and latitude were not significant.On the small scale,the climatic factors and genetic diversity of the four populations,Fenyi,Shuangpai,Youxian and Rongshui were similar with the low altitude range,showing higher genetic diversity,and the correlation with the altitude gradient were not significant,while the high altitude of the Rongshui population showed a low level of genetic diversity due to low temperature and high humidity.(4)The correlation analysis between climatic factors and genetic diversity parameters showed that Shannon's information index(I)hadsignificant positivecorrelation with extreme maximum temperature(MVMT),mean temperature of July(TAV07)and possible evapotranspiration(PER),while significant positivecorrelation with kira cold index(CI),and negatively correlation with the wetting index(HI)and relative humidity(RH)of Xu Wenduo,while negativecorrelation with dryness(K).There was a significant positive correlation between expected heterozygosity(He)and PER,and negative correlation with dryness(K),and significant positive correlation with MWMT,annual temperature difference(TD),summer heat and humidity ratio(SHM)and TAV07;It showed that with the rising of temperature,annual temperaturedifference and dryness while the humidity decreaseswill lead to the increasing genetic diversity of T,mairei.The correlation between the fixed index(F)and the whole climatic factors were not significant,indicating that the climatic factors had little effect on the reproductive mating pattern of T.mairei,inferring that geographical isolation,human disturbance and other factors had a great influence on the reproductive mating system.(5)On the whole,the populations showed abundant genetic diversity,and the differentiation among populations was obvious(Fst=0.251,Nm<1).The protection strategies could be protected in situ,assisted with artificial regeneration,and maintained the genetic diversity of populations. |
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