极小种群野生植物显脉木兰的保护遗传学研究

	极小种群野生植物显脉木兰的保护遗传学研究
	杨丰懋
导师	孙卫邦
关键词	保护遗传学，简化基因组，种群历史动态，极小种群野生植物，显脉木兰 Conservation genetics, RAD-seq, Demographic history, Plant Species with Extremely Small Populations, Magnolia fistulosa
摘要	显脉木兰Magnolia fistulosa (Finet & Gagnepain) Dandy为木兰科 (Magnoliaceae) 木兰属常绿灌木或小乔木。其叶片浓绿硕大，花朵白色，开放时香味浓郁，在木兰科中具有较高观赏价值。显脉木兰在云南的分布极为狭窄、分布点有限且受人为干扰严重。在《云南省极小种群野生物种拯救保护规划纲要 (2010–2020年)》和《云南省极小种群野生植物保护名录 (2021版)》中，显脉木兰均被列为极小种群野生植物。本研究对分布于中国的显脉木兰种群进行调查，并采用双端简化基因组测序 (double digest restriction‐site associated DNA sequencing; ddRAD-seq) 的方法研究了该物种的遗传结构、基因流、遗传多样性、当代有效种群大小和种群历史动态，研究主要结果如下。 1. 遗传结构和近期基因流显脉木兰的七个分布点可被划分为四个遗传单元和五个保护单元。近期基因流分析显示，虽然河口和马关的显脉木兰分布点间的距离并不遥远 (<15km)，但其间却呈现出较少的近期基因流。遗传距离与地理距离相关性分析显示显脉木兰分布点间的遗传距离与地理距离呈现显著的正相关性。 2. 遗传多样性与当代有效种群大小与一些濒危植物相比，显脉木兰在物种水平具有较高的核苷酸多样性 (0.072)，但现有分布点间的核苷酸多样性 (0.030–0.068) 和当代有效种群大小 (2.0–68.0) 差距较大。显脉木兰金平种群的核苷酸多样性明显低于河口和马关，表明应进行必要的遗传拯救。 3. 种群历史显脉木兰的种群历史推测显示，其种群在一百万年 (Ma) 内经历了多次下降，包括0.5–0.8 Ma、0.2–0.3 Ma、0.02–0.03 Ma。前两次种群下降可能对应各自时期全球范围的气温下降，而最近一次种群波动可能由于末次盛冰期的普遍降温。在末次盛冰期后，显脉木兰的历史有效种群大小回升到较高水平。人类活动对显脉木兰及其生境的破坏应是其致濒的主要因素。 4. 保护建议对大围山国家级自然保护区和古林箐省级自然保护区内显脉木兰的退化生境进行恢复和增强回归以促进分布点间的基因流，并为金平荞菜坪的孤立种群设立保护小区。收集显脉木兰迁地保护种质资源时，应将个旧清水河和金平荞菜坪分布点作为独立的遗传单元分别进行收集。对分布于河口和马关的分布点，应将古林箐马草坪、白沙河以及河口中部的显脉木兰视作同一个遗传单元进行收集，而将河口坝洒、河口龙堡的显脉木兰种质资源分别收集。显脉木兰金平荞菜坪种群的遗传多样性相比于马关和河口的种群出现明显下降，且该种群植株数量稀少，与其他种群有较远的地理隔离，建议利用马关马草坪分布点的个体对其进行遗传拯救。; Magnolia fistulosa (Finet & Gagnepain) Dandy is an evergreen shrub or small tree in Magnoliaceae. With broad oval leaves and extremely aromatic flowers, M. fistulosa has high horticultural values. The distribution areas of M. fistulosa in Yunnan is extremely narrow, with limited distribution points and serious anthropogenic disturbance. M. fistulosa was classified as a Plant Species with Extremely Small Populations (PSESP) in the Planning Outline of Rescuing and Conserving Yunnan’s PSESP (2010–2020) and in List of Yunnan Protected Plant Species with Extremely Small Populations (2021). This study investigated the distribution of M. fistulosa in China, using the double digest restriction-siteassociated DNA-sequencing (ddRAD-seq) method to study its population divergence, gene flow, genetic diversity, contemporary effective population size and demographic history. The main results are as follows. 1. Genetic structure and recent gene flow The seven distribution points of Magnolia fistulosa can be can be divided into four genetic groups and five conservation units. Recent gene flow analysis showed that although the distance between the distribution points in Hekou and Maguan is not far (<15km), there were less recent gene flow among them. Mantel test between the genetic distance and geographic distance showed that the genetic differentiation between the distribution points of M. fistulosa was significantly positive correlated with geographic distance. 2. Genetic diversity and contemporary effective population sizes Compared with some endangered species, Magnolia fistulosa has higher genetic diversity (0.072), but the genetic diversity (0.030–0.068) and the contemporary effective population sizes (2.0–68.0) in existing distribution points are quite different. The genetic diversity of M. fistulosa in Jinping population is much lower than that of plants distributed in Hekou and Maguan, suggesting that necessary genetic rescue should be carried out. 3. Demographic history Changes in the effective population size of Magnolia fistulosa within 1 Ma were detected, including three population decline about 0.5–0.8 Ma, 0.2–0.3 Ma and 0.02–0.03 Ma. The first two population declines may correspond to global temperature declines during their respective periods, while the most recent population fluctuations may be due to general cooling during the Last Glacial Maximum. The effective population size of M. fistulosa recovered after the last glacial maximum. The endangered status of M. fistulosa may due to the destruction of its habitat by human activities. 4. Protection recommendations Restoration and reinforcement of the degraded habitats of Magnolia fistulosa in the Daweishan National Nature Reserve and Gulinqing Provincial Nature Reserve to promote the geneflow between the distribution points and set up a mini-reserve for the isolated population of Qiaocaiping, Jinping. When collecting the genetic resources of M. fistulosa for ex situ conservation, individuals i
语种	中文
	2022-05
学位授予单位	中国科学院大学
文献类型	学位论文
条目标识符	http://ir.kib.ac.cn/handle/151853/75175
专题	昆明植物所硕博研究生毕业学位论文
推荐引用方式 GB/T 7714	杨丰懋. 极小种群野生植物显脉木兰的保护遗传学研究[D]. 中国科学院大学,2022.

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