Population Dynamics And Genetic Differentiation Analysis Of Metapetrocsmea Peltata(Gesneriaceae),an Endemic Herb In Hainan Island

Metapetrocosmea peltata(Gesneriaceae)is an endemic species widely distributed in the middle and southern mountainous area of Hainan Island.It is an ideal material for studying the impact of the geographical isolation on pattern of genetic diversity.In this study,population dynamics of different geographical populations on both sides of the Changhua River valley were studied by age structure,static life table and survival curve analysis.Then,the amount and distribution of genetic diversity of M peltata were stLidied based on three chloroplast fragments and internal transcribed spacer(ITS).The main results are as follows:(1)The results of population dynamics analysis of five geographical populations of M.peltata on both sides of the Changhua River valley indicated that the habitat of QX and LM were more suitable for the early-age plants;there are many early-age plants in these areas,showing a growth population.M.peltata has a large population in both WZ and JX,and the population belongs to a stable population.The population of M.peltata in XA is small,low in altitude and vulnerable to human disturbance.The population is gradually declining and suitable conservation measures should be taken.On the whole,the population of M.peltata is stable at present,and the difference between the two sides of Changhua River valley has little effect on this species.(2)We collected 172 M.peltata individuals from 12 natural populations,and assessed the genetic diversity and differentiation of this species based on sequence variation of cpDNA fragments(ndhC-trnV/trnL/ycf1b)and nrDNA fragment(ITS).At the level of cpDNA,there was high genetic diversity at the species level(HT=1.000,?=0.0061)and high divergence among populations(GsT=0.447);average gene flow among populations was very low only 0.08;the results showed that 81%of the genetic variation among populations,and there was no haplotype shared among the populations;Structure analysis results also showed that most populations were composed of their unique genetic components,which was supported by the haplotype network analysis and clustering analysis based on Nei's genetic distance.The Mismatch curve was multi-peak,indicating that the population was stable and did not expand recently.At the level of nrDNA,the genetic diversity at the species level was also high(HT=0.993,?=0.0235);The genetic differentiation of the population was high(GST=0.370)and the gene flow was small(Nm=0.12).;Structure analysis clustered individuals of M.peltata into six genetic groups,whose geographic distribution is largely concordant with the isolation pattern of Hainan mountainous area caused by Changhua River.The geographic distribution of genetic clusters was further supported by population cluster analysis based on Nei's genetic distance.This study manifests the isolation effect of Changhua River on the distribution of genetic diversity of M.peltata AMOVA showed that 69%genetic variation was partitioned among populations,suggesting genetic differentiation of this species was mainly caused by geographic isolation.On the whole,the population of M.peltata has high genetic diversity and strong genetic differentiation.The gene flow of the cpDNA fragment is more limited than that of the ITS of nrDNA,which may be due to the pollen diffusion is easier than the seed dispersal.Therefore,cpDNA shows stronger genetic differentiation,and the total analysis of cpDNA and nrDNA will more comprehensively reveal the evolutionary history of M.peltata population.In conclusion,most of the M.peltata is a stable population at present.The geographic isolation of Hainan mountainous area caused by Changhua River and its tributaries should be the driving force for the strong genetic differentiation among M.peltata populations,and also may lead to the high genetic diversity detected at the species level of M.peltata.This study not only provides recommendation for efficient conservation and utilization of M petata,a potential ornamental plant species,but also facilitates the understanding of geographic distribution of genetic variation for Hainan Island endemic and other plant species.