Study On The Genetic Diversity And Strategy Of Conservation Sampling For Natural Population Of Davidia Involucrata

Davidia involucrata is a species that is specially distributed in China and belongs to Davidia and Nyssaceae. It has epibiotic origin and is relic species from tertiary palae-tropical flora. It also has been called as "Chinese pigeon tree" owing to elegant tree gesture and striking inflorescence that looks like flying by white pigeon with expanded wing. The Davidia involucrata has very high academic position in research on development of plant system and alternation in the history of the earth. At present, it is only sparsely-distributed in China and has been presently listed as first class of protective, rare and endangered plant in China.This research conducted species studies of Davidia involucrata on genetic diversity and conservation of germplasm resource mainly from three aspects:(1) Detection of genetic diversity within and among 5 natural populations of Davidia involucrata distributed in China has been carried out by use of RAPD molecular marker, the genetic variation from DNA level was elucidated;(2) Effect of different sampling methods on population genetics parameters has been detected;(3) Sampling strategy on core collection for conservation of germplasm resource to Davidia involucrata in China has been put forward based on research on genetic diversity among Davidia involucrata from DNA level.The research results are as follows:(1) 13 primers that can produce polymorphic, clear and bright bands, sound repeatability have been selected for RAPD amplification and analysis on DNA samples in 5 Davidia involucrata populations from 40 random primers.(2) Totally 101 polymorphic markers were obtained through carrying on amplification on 186 samples by use of the 13 selected polymorphic primers, in which each primer can yield 7.78 polymorphic loci averagely. The percentage rate of polymorphic loci in 3 populations from Emeishan of Shichuan Province, Fanjingshan of Guizhou Province and Shengnongjia of Hubei Province are significantly higher thanthose from Xuan'en of Hubei Province and Wenxian County of Gansu Province.(3) There exist broader variations among genetic diversity of all populations. Those of populations from Fanjingshan of Guizhou Province, Shengnongjia of Hubei Province and Emeishan of Shichuan Province are obviously broader than those from Wenxian County of Gansu Province and Xuanven of Hubei Province. The average genetic diversity within species of Davidia involucrata is 0.3345, but 0.2476 for that within population, and 0.0869 for that among populations. The coefficient of genetic differentiation has reached up to 0.2599, and gene flow has arrived at 1.4239. It is indicated that 26% of total variation for genetic variation among populations and genetic differentiation among population is relatively larger because of being short of effective gene flow due to influence by minor population effect and scattered distribution for Davidia involucrate, though most of variation in Davidia involucrata exists within the population.(4) There are higher genetic similarities among 5 populations of Davidia involucrata, all of which is above 0.8, but the largest one has reached 0.9321 in 2 populations from Fanjingshan of Guizhou Province and Shengnongjia of Hubei Province. The next is 0.8878 in 2 populations from Xuanxen and Shengnongjia of Hubei Province and the smallest one is 0.8141 in populations from Xuan'en of Hubei Province and Wenxian County of Gansu Province.(5) It has been shown according to cluster dendrogram that the 5 natural Davidia involucrata populations can be divided into 2 big groups i.e first group from Xuanen, Shengnongjia and Fanjingshan; second group from Emeishan and Wenxian. Therefore, we can divide it into 2 provenance regions i.e southeast region and northwest region.(6) Differentiation among populations from Xuanven of Hubei and Wenxian of Ganshu estimated by use of Shannon index are significantly higher than coefficient of gene differentiation for total populations, but all the 3 populations from Emeishan, Fanjingshan and Shengnongjia are lower than that of total population. However, whatever comparison is made in any case, the genetic diversity is mostly existed within population, genetic diversity for total population is only accounted for 25-26% by genetic diversity among populations, the 2 conclusions are identical.(7) The genetic similarity between two of them has been calculated based on data from RAPD molecul marker to 54 plants of Davidia involucrata in sample plot, so cluster program has been obtained, and regards small cluster groups with higher similarity as a neighborhood, also could obtain schematic diagram neighborhood of Davidia involucrata, therefore it can calculate that area (diameter) of neighboring regionfor Davidia involucrata is 15-30 m and average is 25 m.(8) It might be known that reliability of polymorphic loci for 3 populations through random sampling might reach 99% according to capturing curves established from sampling size of Davidia involucrata populations and percentage of polymorphic loci. The reliability of 25 individuals through random sampling within the populations reached over 95%, while 30 individuals from random sampling might reach 99%.(9) Through detecting influence on genetic parameters for population of the results indicate that the influence of numbers for effective alleles (Ne) and gene diversity degree (h) on is very small, while sample number influences the coefficient of differentiation Gst between populations and estimation of Nm value of gene flow obviously.(10) Strategy for conservation sampling of core collection through analysis on genetic diversity of Davidia involucrata and study on population genetic structure can be obtained accordingly. The sampling strategy for conservation in original place: 3 populations from Wenxian County of Gansu Province, Emeishan of Sichuan Province and Fanjingshan of Guizhou Province were selected as conservation object with conserved area of above 3 hm2 for each population. The sampling strategy for conservation, ex situ: sampling 4 populations from Wenxian County of Ganshu Province, Emeishan of Sichuan Province, Shengnongjia of Hubei Province and Fanjingshan of Guizhou Province with 30 sampled individuals for each population, the smallest plant space of above 30 m among each individual and total conservation number of 150 individuals (> 4 x 30) and establishing one ex situ conservation site respectively in Southeast and northwest China.