A Study On The Conservation Genetics Of Ostrya Rehderiana Chun.

Ostrya rehderiana Chunis one of the most endangered plant species in China, currently only 5 individuals in the wild. Since 1980s, some seeds were collected, and germinated ex situ. Nowadays, there are about 175 artificial individuals. Although seed germination technique had been developed well and the artificial population expanded, no genetic information has been studied till now. Conservation of O. rehderiana population without knowledge on its genetic information would be less effective.In this study, AFLP was employed to reveal the genetic diversity of the natural population, to assess whether genetic diversity declines in the artificial population. Parentage analysis was done to compare the offspring number of each natural individual and different parent pairs.The percentage of polymorphic bands is 29.9% in natural O. rehderiana population, and 41.18% in artificial O. rehderiana population. The effective allele number for natural and artificial population were 1.242 and 1.208 respectively. The avrage null bands in natural population is 23, and in artificial population is 43.8.The expected heterozygosity were 0.381 and 0.184 by Bayesian method for natural and artificial population respectively. Moreover, based on Bayesian method, the estimated effective population size is only 1.We found that the genetic diversity of natural population is very low, deduced that is the nature of O. rehderiana and the habitat loss lead. Base on the essential enviromental factors in the life history of Ostrya rehderiana, there is a tendancy of forming scattered small population. This distribution pattern will influence genetic structure. After habitats were destructed, only several individuals in a single population survived, genetic diversity lost.In the artificial population, heterozygosity decreased significantly, and the increase in null homozygotes was observed. The deduced reason is the low level of genetic diversity in the natural population. The genetic difference between parents is too low, bringing a similar result to inbreeding, leading to the rise of homozygosity. Thus, the positive bands shared by natural ones and the artificial ones decreased and the similarity between them is lower. As a result, the natural ones and the artificials are clustered to two separate branches in the cluster analysis based on Jaccard similarity.Parentage analysis show that all natural individuals have some descendants, but different parent pairs are distinctive in offspring number, ranging from 1 to more than 30. Parent pairs with higher genetic similarity tends to have less descendents, even if being influenced by the seeds number of each individual.