Genetic Diversity And Spacial Genetic Structure Of Endangered Species Heptacodium Miconioides

Heptacodium miconioides, an edemic plant of Heptacodium in Caprifoliaceae with limited distribution and restricted population number, had been listed as a member of the national class II protective plants. H. miconioides discontinuely distributed in Zhe jiang Province and An hui Province. ISSR and cpSSR molecular markers were used to analyze the genetic diversity and spacial genetic structure of H. miconioides. The aim of the study were to elucidate the endangered mechanism of H. miconioides and provide scientific strategies for the endangered speices through exploring the genetic differentiation of small-scale populations and the gentic diversity of chloroplast DNA. The results were showed as the follows.1. The genetic diversity and genetic differentiation of H. miconioides in five populations in Tiantai County were analyzed using ISSR markers. The total percentage of polymorphic loci of H. miconioides was 58.17% at moderate level. The genetic diversity of SZYK population was the highest (41.18%) and that of ZXC population was the lowest (33.33%). The gene differentiation (GST) was significant (0.3497), and the limited gene flow estimated by GST was 0.9299. DML population and CS population gathered together into one group first, while ZXC population, SZYK population and HJD population gathered together into another group. This might due to the heterogeneity of the microenvironments.2. The genetic diversity of the chloroplast DNA of H. miconioides was analyzed using cpSSR molecular markers. No cpDNA variation was detected in the study, indicating that all of the individuals shared the same maternity and originated from a large population after glaciations, which were similar to the other studies.3. Fine-scale spacial genetic structure of H. miconioides was analyzed using ISSR molecular markers and the correlation between the genetic distance and geographic distance was explored. There was significant spatical genetic structure at 0~8.06m distance class showing aggregration distribution pattern. And the spacial genetic structure at the other distance classes was not significant. The spacial genetic structure of I age class was significantly at 0~4.36m, and that ofâ…¡age class was 0~6.42 m, that ofâ…¢age class was 0~3.3m, and that ofâ…£age class was 0~8.06m. With the decreasing of the age, the distance showing significant genetic structure increased with more similar genotype aggregated together with limited gene flow. This might be due to the limited pollen dispersal distance, the heterogeneity of the microenvironment and inbreeding depression.4. The genetic diversity at species level was relatively high and that at population level was low, which might be the main cause for the endangered species. Based on the spacial genetic structure, the low genetic variation resulted from limited gene flow might be the main cause for the endangered of the species. The effective conservation strageis for this endangered species were put forward based on study results, such as enhancing pronounce, decreasing human destroy, expanding population size, increasing gene flow by outbreeding among populations, progressing research of reproductive ecology and developing in-situ conservation and ex-situ conservation.