Genetic Structure Of Heptacodium Miconioides And Identifying Populations For Priority Conservation

Heptacodium miconioides is a nation-level endangered plant species, endemic to China. Due to anthropic disturbance, it was disappeared in Hubei Province where the modal specimen was collected; only about 10 populations were remained in Zhejiang and Anhui Province, and population size ranged from less than 20 to several hundreds. Of the remaining populations, two are located in reserves, and others received no effective conservation. As indicated by other studies, population genetic information plays a critical role in the conservation. However, no genetic studies were reported in H. miconioides.In this study, we analyzed the genetic diversity and genetic structure of 9 remaining populations in H. miconioides. We also constructed a population genetic contribution model which can be used to estimate the contribution of each population to species-level genetic variation. Using this model and RAPD-based genetic variation, we identified populations for priority conservation in H. miconioides and suggested several conservation implications for H. miconioides.A total of 10 primers were used, which produced 75 bands in all the 241 individuals of 9 populations tested. At species level, the percentage of polymorphic loci (92%), the number of effective alleles (1.45), the Nei's genetic diversity (0.2929) and the Shannon index (0.4112) were all higher than those of most endangered plants. Relative high genetic variation was due to the strong ability of coppicing from older stems. This ability decreases the negative effects of drift and inbreeding on genetic diversity in small populations.Most variation in H. miconioides was found within (75.14%) rather than among populations as estimated by AMOVA analysis. The gene differentiation (GST=0.2569) also shows the same result. Mantel test indicated significant relationship between differentiation and geographical distance in H. miconioides. The strong relation between genetic diversity within populations and estimated population size was also found in H. miconioides. These results interpreted that the gene flow, other than drift and inbreeding, plays a critical role in the genetic structure of H, miconioide.The genetic contribution of a population to species depends on two parts: one is the genetic variation within the population and the other is the genetic differentiation compared with otherpopulations. Two models of population genetic contributions, based on allele richness and Nei's genetic diversity, respectively, were constructed. The estimates of the parameters in the models were given according to different molecular markers. By using the population genetic contribution models, we found that the populations located in Qingliangfeng, Dapanshan, Simingshan, and Tiantaishan were the most important on maintaining genetic diversity of H. miconioide, and should be conserved with higher priority.