Genetic Diversity And Conservation Biology Research Of Davidia Involucrata

Dove tree (Davidia involucrata) is a relic plant endemic to China surviving from the Tertiary and is reputed to be a ’living fossil’ plant in the plant kingdom. It is a rare and endangered plant listed as the first-grade plants of national protection. Dove tree is beautiful in appearance, and has a pair of white bracts on the base of inflorescence, which looks like wings of group dove in flower season. Thus, it has the laudatory name of "the Chinese dove tree". Dove tree has important scientific research and landscape plants development and utilization value. In this paper, the community type, distribution pattern, population structure, genetic diversity, reproduction and species reintroduction were investigated to analyze the population ecology and genetic structure of Dove tree and to provide a theoretical basis for the germplasm protection. The main results were presented as following:1. Community structure analysis. Three plots have been selected based on forest composition and habitat differences via the typical sampling method in GaoQiaoHe, QingShuiHe and HuangShaHe basins in LongCangGou, Daxiangling nature reserve. The height, crown width and diameter at breast height (DBH) of the woody plants greater than2.5cm were measured. The1m×1m small plot was setted in lower left corner in each5m×5m quadrat and the plant species name, average height and total coverage of herb layer were recorded. The community types were classificated according to the important value of plant in every layer. The results showed that three new community types were classificated in the three regions. The appearance, structure of each community types was analyzed and the corresponding protection strategies were proposed.2. Studies on the spatial distribution pattern of Davidia involucrate. The spatial distribution pattern of population was studied based on the data of sample field investigation and the theory of discrete distribution and the assemble intensity. The results indicated that the spatial distribution of D. involucrata population is a clumped pattern and it has strong assemble intensity in seedling and young tree phrase because of difficult spread of seed and regeneration by tillering. The distribution pattern changes from clumping to random gradually from the young tree to old tree because of the competition and high death rate of young tree.3. Population structure analysis. The age structure of the dove tree populations and their succession trends were discussed based on the DBH structure, the height structure, the static life table and the survival curve of the dove treepopulations. The result showed that the population structure is growth or steady in this region. The mortality rate is high of seedlings and young trees, and then after reaching a certain diameter, the population remained stable state relatively.4. Genetic structure analysis. Genetic diversity and genetic structure of Dove tree were analyzed for its conservation and management, using Inter-simple sequence repeat (ISSR) data obtained from eight populations distributed throughout seven provinces of China. A relatively high level of genetic diversity, at both population and species levels, was detected using POPGENE software. Analysis of Molecular Variance (AMOVA) revealed a moderate level of among-population variation (i.e.33.21%). The genetic structure of dove tree was closely consistent with their isolated topographical distribution region based on the results of the STRUCTURE, POPGENE-UPGMA and PCA analysis. It is postulated that the relatively high level of genetic diversity has been maintained because of:a) the original wild geographical distribution, b) propagation through outcrossing seeds or root suckers, c) the longevity of individuals, and d) relatively little human disturbance. Genetic drift and restricted gene are important factors affecting genetic differentiation. There was no significant correlation between geographical distances and a pairwise comparison with genetic distances as analyzed by the Mantel test, but the clustering result of genetic diversity was consistent with their isolated topographical distribution regions. Thus, maintaining the stable special habitats associated with this species is recommended for the in situ conservation. Furthermore, it is important to develop an effective seed germination system for the maintenance of an ex situ conservation pool of the germplasm resources.5. Propagation technology of Davidia involucrate. Scholars carried out a substantial amount of researches on seed dormancy and germination of Dovetree for many years, both at home and abroad. Many methods of seed germination have been reported, such as the mechanical damage, chemical reagent, immersion in human and animal urine and so on, but it was found out that stored seed in wet sand for a long time is still the best method, which could reduce the mechanical resistance of seed germination and the completion of after-ripening seeds,It can not only significantly improve the rate of seed germination, but also improve the uniformity of germination.10,000seedlings was produced from stored seed in wet sand for a long time, and2000seedlings were reintroduced to Xingdoushan, Qizimeishan and Badagongshan nature reserve.