基于基因组水平的华木莲种群动态历史研究

Studies on population demographic history are essentially important for elucidating the hisrotical factors responsible for the change in effective population size, range shift and population differentiation of an endangered species. Sinomanglietia glauca (syn. Manglietia decidua) is an endangered plant in southeast China. Due to its limited population size and great scientific values, this species is listed as Category I of the National Key Protected Wild Plants in China. Since the discovery of S. glauca, its genetic diversity and genetic structure have been investigated by different research groups using chloroplast, SSR and other molecular markers. In these studies, climatic change and anthropogenic fragmentation; are suggested to be the causes of the endangered status of S. Glauca. However, the details of demographic history, which are relevant to the conservation of this endangered species, remain vague because of the poor informativeness of molecular markers and simple analytical methods used in previous studies. In this project, we'd like to acquire genomic data of this species through RAD-sequencing method. In addition, population demographic history (population divergence time, the change in effective population size, etc.) will be inferred and simulated by means of several coalescence-based methods, such as ABC, IMa and dadi. The results of this project would clarify the key historical factors responsible for the population decline of S. glauca, and help strategize to preserve the genetic diversity and evolutionary potential of this endangered species. Moreover, this study will foster the development of population genetics and phylogeography of China in genomics era.

解析濒危物种的种群动态历史可以推测影响其有效种群大小、分布范围和种群分化的历史因素，从而解答濒危物种的濒危机制。华木莲（也称落叶木莲）是我国一级重点保护植物，前人群体遗传学结果显示，华木莲目前的濒危状态可能是自然和人为因素导致其种群收缩的结果。然而，由于前人研究采用的DNA序列（或分子标记）信息量较低，分析方法较为落后，这些研究没有明确其种群如何分化以及种群动态历史细节，我们也无从得知自然因素与人为因素在其濒危过程中的相对贡献。有鉴于此，本研究拟采用简化基因组RAD测序方法，获得华木莲高通量基因组数据，通过先进的基于溯祖理论的统计模型分析方法，重演华木莲种群动态历史过程，找到影响其种群分化和种群衰退的关键因素，为华木莲保护提供科学依据。本研究结果对于基因组时代濒危物种保护遗传学和谱系地理学研究也将具有重要借鉴意义。

解析濒危物种的种群动态历史可以推测影响其有效种群大小、分布范围和种群分化的历史因素，从而解答濒危物种的濒危机制。华木莲（也称落叶木莲）是我国一级重点保护植物，前人群体遗传学结果显示，华木莲目前的濒危状态可能是自然和人为因素导致其种群收缩的结果。然而，由于前人研究采用的DNA序列（或分子标记）信息量较低，分析方法较为落后，这些研究没有明确其种群如何分化以及种群动态历史细节，我们也无从得知自然因素与人为因素在其濒危过程中的相对贡献。有鉴于此，本研究拟采用简化基因组GBS测序方法，获得华木莲高通量基因组数据，通过先进的基于溯祖理论的统计模型分析方法，重演华木莲种群动态历史过程，找到影响其种群分化和种群衰退的关键因素，为华木莲保护提供科学依据。获得的主要结果如下：.1）.华木莲系统发育关系.本研究选取10个木兰科物种，即北美鹅掌楸、中国鹅掌楸、木莲、巴东木莲、三瓣木兰、西康玉兰、黄山木兰、玉兰、天目玉兰和厚朴。华木莲三个居群江西宜春玉京山采集8个个体，湖南小溪乡采集6个个体，朗溪乡采集8个个体，总计22个个体。简化基因组数据显示华木莲与木兰属较近，与木莲属较远。该结果需要进一步证实。.2）华木莲种群动态历史.对华木莲三个群体22个个体进行简化基因组测序，获取270万个SNP。结果显示华木莲种群数量从200kya开始经历了三次种群收缩，即100-200 kya经历了第一次种群数量下降，并在大约40-50 kya种群数量开始第二次下降，在大约20-30kya种群数量第三次下降种群数量保持稳定，种群大小缩减了20倍以上。更新世末期至全新世以来的气候变化造成了华木莲群体收缩和片段化，而人为因素进一步加剧了部分谱系的急剧收缩。.本研究结果对于基因组时代濒危物种保护遗传学和谱系地理学研究具有重要借鉴意义。