The Research On Genetic Diversity And Molecular Phylogeography Population Of Taihangia Rupestris Yu Et Li

Taihangia rupestris Yu et Li is an perennial herb endemic to China. T. rupestris is the most primitive diploid species(2n =l4) in the tribe Dryadeae belong to the family Rosaceae according to its morphology, anatomy of carpel, chromosome counting, microscopic and submicroscopic structure of pollen, so it is an ancient relic species. T. rupestris, with the characterization of evolvement from bisexual flower to unisexual flower, is at an important systematic position in the tribe Dryadeae, and study on it could throw a new light on evolution of the tribe Dryadeae.Microsatellites marker based on nuclear genes was used to research the genetic diversity and genetic structure of T. rupestris populations. Meanwhile, associating with the analysis of cholorplast DNA multisequence variations, we would explore procedure of dynamic history of the level of T. rupestris sepecies and the population level, which providing the basic information of population genetics for designing the genetic resource conservation strategy of T. rupestris. The major findings are as follows:(1) A total of 224 individuals from 10 populations in China were investigated using 10 pairs of SSR loci. High genetic diversity(0.773)was detected in species. AMOVA revealed that 81.49% variation exists within populations. Low genetic differentiation among populations was detected with FST =0.1792, GST =0.177. Gene flow(Nm) among populations was estimated to be 1.0536.(2) The UPGMA analysis clustered 10 populations into two groups. GroupⅠ contained populations DPB, YDS, LHP, QPG, XXT and HHS. Group Ⅱ included other four populations. Structure analysis revealed two major phylogeographical groups in China: Southern and Northern populations. These results analysis supports the results of UPGMA clustering, Southern and Northern populations had their own source of their ancestors.(3) The mantel test showed that there was significant positve correlation between geographical distance and genetic distance(r =0.597, P<0.001), indicating the role of geographic isolation in shaping the present population genetic structure of T. rupestris.(4) Bottleneck test showed that 7 populations(DPB, YDS, LHP, QPG, JG, NY, DLG) experienced the bottleneck effect based TPM and SMM model.(5) After a preliminary survey on 20 chloroplast DNA regions, we obtained four chloroplast fragments, then amplified and sequenced these four fragments for 220 individuals of 10 populations.Nucleotide diversity and haplotype diversity are π=1.37×10-3 and Hd =0.729 respectively. The total diversity(HT =0.803) was high while the within-population diversity(HS =0.017) was low. Molecular variation analysis(AMOVA) results revealed a high level of genetic differentiation(90.72%) among populations. The estimates of interpopulation differentiation were very high(GST =0.979, FST =0.995, NST =0.996). Further, GST being the same as NST(P>0.05) suggested a non-phylogeographical pattem whereas the value of average gene flow(Nm =0.01) was low. Mantel test(r =0.204, P>0.05) showed the populations are lack of apparent phylogeographical structure.(6) A total of 9 variation sites were detected, which gave rise to a total of 7 cp DNA haplotypes. Similar to the chlototypes network, haplotype phylogenetic analysis recognized that seven chlototypes clustered into three clades. Basic clade contained the haplotype that fixed in the Southern populations and Northern populations, the second clade contained the haplotype which only found in the Southern and Northern populations, the third clade contained the haplotypes that distributed in the SSM population.