Conservation Genetics And Molecular Phylogeography Of Dysosma Versipellis (Berberidaceae), An Endemic And Endangered Plant From China

Dysosma versipellis is an endemic endangered plant in China.The determination of genetic diversity,population structure,glacial refugia and historical processes which D.versipellis has undergone are of crucial importance in order to put forward feasible conservation strategies.Our present work investigated the factor induced rarity of D.versipellis.The analysis was carried out based on cpDNA trnL-trnF, trnL-ndhJ,trnS-trnfM intergenic spacer,Amplified Fragment Length Polymorphism (AFLP) and breeding system.Genetic diversity and population structure were detected in combination with the ecological investigations,population evolutionary history.Consequently,conservation strategies are proposed.There are 4 main conclusions of our research:1.Breeding system and pollination biologyD.versipellis is in flower from early April to July with a peak in May.The process of flower anthesis in D.versipellis lasts about 10-12 days.The number of pollen grains and ovules per flower is averaging 1060008±44184.13 and 50.7±1.94, respectively.The Pollen-ovule ratio(P/O) calculated is high,averaging 20933.7±844.89.Although Chrysomya megacephala(Calliphoridae) is the most common visitors,pollen transfer in this species is not highly effective and principally occurs by Longhorned beetle(Cerambycidae).Breeding system experiments showed that the mean(±s.e.) fruit set(%) under natural condition(11.8±2.4%) is less than that resulting from manual cross-pollination(62.7±4.1%).It is concluded that D. versipellis is self-incompatible,and pollinator-dependent for sexual reproduction,and lack of xenogamous pollination limits fruit formation in populations of D.versipellis. Thus,the identification and translocation of compatible mating types to create reproductively viable populations is essential for the recovery of D.versipellis.2.cpDNA genetic diversity and phylogeographic structureTen populations were analyzed using cpDNA trnL-trnF,trnL-ndhJ,trnS-trnfM intergenic spacer.A total of 2873 bp and 33 variation sites were detected,which gave rise to a total of 24 cpDNA haplotypes.Nucleotide diversity and haplotype diversity areπ=0.236×10^-3 and h=0.394 respectively.In wersten China,Nucleotide diversity and haplotype diversity areπ=0.000125 and h=0.329,respectively.In central/eastern China,17 haplotypes were found,Nucleotide diversity and haplotype diversity areπ=0.000264 and h=0.408.AMOVA revealed 86.8%variation exist among populations.High genetic differentiation was detected(F_ST=0.868,G_ST=0.60) among populations.The genetic differentiation was lower than that of cpDNA.When populations were grouped according to the major phylogeographic break identified by BARRIER,hierarchical AMOVA found 59%of the total cpDNA sequence variation distributed among western vs.central+eastern groups,33%was explained among populations within each group,and only 8%within populations.Neutrality test and mismatch distribution support significant postglacial population expansion of D. versipellis in China.The cpDNA data presented showed the near complete fixation of two major haplotype lineages in western vs.central/eastern populations.Irrespective of the outcome of such prospective studies,the two cpDNA lineages identified in D. versipellis should be taken into consideration as 'Evolutionarily Significant Units' in any program aimed at conserving genetic resources of this rare and endangered species.3.AFLP genetic diversity and population genetic structureA total of 184 individuals from 9 populations were investigated.Eight primer combinations produced 406 fragments,among which 89.66%are polymorphic.High genetic diversity was detected in western population DJ(h=0.1537),EM(h=0.1408). Low genetic diversity was detected in the central/eastern populations of SX (0.0379),TT(h=0.0388).High genetic differentiation(58.56%) among populations was detected with F_ST=0.586.The genetic differentiation was lower than that of cpDNA.Hierarchical AMOVA found 37.02%of the total cpDNA sequence variation distributed among western vs.central+eastern groups,30.69%was explained among populations within each group,and 32.29%within populations.UPGMA,principal coordinate analysis and misture analysis revealed two major phylogeographical groups:western China,central/eastern China.The result of AFLP indicated that western and central/eastern populations should be taken into consideration as 'Evolutionarily Significant Units'.4.Population history and implication on conservationIn terms of speciation processes,we propose that the deep cpDNA divergence of western and central/eastern lineages of D.versipellis renders this species at an incipient stage of allopatric speciation,whereby climate-induced eco-geographic isolation through(a) biotic displacement of temperate-deciduous forested habitats (almost entirely) prevented gene flow during and after the separation of these lineages. At smaller spatial-temporal scales,the same vicariance factor seems to have promoted population isolation and divergence in allopatry in the central/east,albeit to a lesser extent.Overall,the molecular data for D.versipellis accord with the premise that Late Quaternary refugial isolation is likely to have enhanced allopatric(incipient) species formation of East Asian temperate plants.Based on cpDNA and AFLP marker,high genetic differentiation among populations was detected.High genetic diversity was found in western China and central/eastern SN and HS populations.The genetic structure detected in this study is critical for the establishment of the conservation strategies.In order to conserve the genetic resources of D.versipellis,The western and central/eastern population should be taken into consideration as 'Evolutionarily Significant Units' in program aimed at conserving genetic resources of this rare and endangered species.We propose that the most desirable populations for the in situ conservation are those in western population(EM/DJ) and central /eastern HS populations.To enhance the adjustability and heterozygous of D.versipellis,gene flow and size of population should be increase.So,to retain as far as possible the genetic diversity of D.versipellis,most of population should be sample in ex situ conservation.And translocation of compatible mating types to create reproductively viable populations is essential for the recovery of D.versipellis.