【作者】 薛辉；

【导师】 鲁长虎；

【作者基本信息】 南京林业大学 ， 野生动植物保护与利用， 2013， 博士

【摘要】 南方红豆杉(Taxus chinensis var. mairei)为我国特有物种。由于生境丢失和片断化,其种群资源急剧下降,已位于濒危的境地,国家已将其列为Ⅰ类重点保护植物。关于南方红豆杉种群资源保护研究已经进行,南方红豆杉的遗传保护研究也逐步展开。微卫星分子标记可用于保护遗传学的研究。微卫星多态性检测技术在保护遗传学中可应用于种群杂合度、历史种群推测、种群异质性分析。微卫星分子标记还可用于生境片断化对物种基因流阻碍作用。本研究采用富集文库法从南方红豆杉基因组中分离多态性位点,为该树种的种群基因流和空间遗传结构的研究提供分子标记。南方红豆杉种群现多已片断化分布,甚至点状化分布,多以小种群形式存在,局限于狭小的分布范围。生境丧失和片断化对物种地理分布和多样性的变化有着至关重要的作用,被认为是威胁生物多样性的构成,结构及功能的主要因素。片断化不仅影响生态系统的种类组成、数量结构、生态过程等因素,同时也关系到物种的种群遗传结构。生境片断化产生的隔离效应亦阻碍了生境斑块间的基因交流,过度近交导致等位基因流失,遗传多态性降低。本研究以南方红豆杉片断化种群为对象,研究片断化对其种群内遗传变异影响以及片断化种群间的基因流和遗传分化。南方红豆杉野生种群片断化程度较高,生长在山地景观中的南方红豆杉种群能否突破山脊线的阻碍实现片断化种群间的基因流?景观遗传学可以分析识别基因流的传播障碍或生境走廊,并可评估预测保护管理方案在景观连接度方面的效果。本研究通过景观遗传学方法分析南方红豆杉的景观遗传结构,验证山脊线对基因流的阻碍作用。主要研究成果如下：1.从南方红豆杉基因组中筛选出11个多态性位点。用32个样本对获得的11个位点进行检测,共计发现等位基因数77个,发现等位基因数最多的为位点Tach9(10个等位基因),最少的为位点Tach1(5个等位基因),各位点平均等位基因数为7。预期杂合度为0.5196至0.8680,均值为0.7548；观察杂合度为0.2500至0.8333,均值为0.6186。分析结果表明PIC值自0.4891至0.8432,均值为0.6233。2.研究了南方红豆杉片断化种群的遗传多样性,结果表明其种群内等位基因数和等位基因丰度均维持在较高水平,杂合度缺乏现象在现有种群中表现不显著。AMOVA分析表明遗传变异主要来源于种群内,揭示种群间的遗传分化没有达到特别显著的趋势,但是南方红豆杉种群间已经表现出一定程度的遗传分化。从种群间遗传分化系数Fst来看最大达到0.4301,总体达到0.141,从基因流来看已有34.8%的两两种群间低于1。结合现存种群片断化严重的实际情况,故而我们认为种群间遗传分化已经在加剧,生境片断化已经阻碍了部分种群间的基因流。3.研究了山地景观中山脊线对南方红豆杉基因流的阻碍作用。Monmonier最大差异算法,SAMOVA算法,以及STRUCTURE和TESS两种贝叶斯分配检验的方法分别对南方红豆杉种群的景观遗传结构进行了分析,识别南方红豆杉种群间的基因流障碍。发现在山脊线(≥700m)两侧的的种群存在相对较强的遗传分化,体现出山脊线对其遗传分化的作用,推断南方红豆杉基因流受到部分山脊线(≥700m)的阻碍。更多还原

【Abstract】 Taxus chinensis var. mairei is an edemic species in China, its populations declined rapidly tothe edge of extinction because of the habitat loss and fragmentation. It s listed as key protectedplant in Class I by Chinese government. Research on conservation strategies of the plantpopulation was in progress, and conservation genetics was also carried out step by step.Microsatellite markers were used for conservation genetics study. Polymorphism microsatelliteloci were suitable for research on heterozygosity, history and heterogeneity of populations.The marker was also used to identify the barrier for gene flow between fragmented populations.We planed to isolate some polymorphism microsatellite loci using enriched library method forthe study on gene flow and spatial genetic structure of the plants. Now, The populations ofTaxus chinensis var. mairei fragmented seriously, even dotted distribution. The species distributedin limited range as small population status. Habitat and fragmentation influenced seriously on thedistribution and diversity of species. It s also regarded as major threaten to the component,construction and function of biodiversity. Not only component, size and process of eco-system,but also genetic structure the fragmentation influence on. Isolation of fragmentation hindered thegene flow between habitat patches and lead to excess inbreeding. Gradually, Allele was lost andgenetic diversity declined. We were interested in the fragmented populations of Taxus chinensisvar. mairei and wanted to know the genetic diversity, gene flow and genetic difference of them.We also wanted to know how the gene flew between the fragmented populations since they werefragmented seriously. Landscape genetics method were used to study whether the ridge ofmountain hinder the gene flow of Taxus chinensis var. mairei. The result conveyed as follows:1. Isolated11polymorphism microsatellite loci from Taxus chinensis var. mairei. Testing the11loci with32samples, we found77allele. There were most allele in Locus Tach9(10allele) andfewest in Locus Tach1(5allele). Mean of allele in all loci is to5. Expected heterozygosity is0.5196to0.8680with a mean of0.7548; Observed heterozygosity is0.2500to0.8333with amean of0.6186The PIC value is0.4891to0.8432with a mean of0.6233.2. Study on the genetic diversity of Taxus chinensis var. mairei in fragmented population. Theresult indicated that number of allele and richness of allele sustain in high level. Heterozygositydeficiency was not significant in the population researched. AMOVA analysis showed thatgenetic variation existed within population, which inferred that genetic differention amongpopulations was not to significant level especially. Meanwhile, Genetic differention amongpopulations has being found to a certain extent. Fixation index Fstamong population is most upto0.4301, Fstin all populations is0.14. Nmvalue between populations which is not up to1hold34.8%. Considering on the fragmentation status of Taxus chinensis var. mairei, We believed that genetic differention among the populations had increased, and the gene flow between somepopulations had been hindered.3. Study on the barrier for gene flow by moutain ridge in mountain landscape. Assignment testwas taken by Monmonier s maximum difference algorithm, SAMOVA, and two bayesianmethods STRUCTURE and TESS to analysis the landscape genetics structure and identify geneflow barrier for Taxus chinensis var. mairei. Through analysis, we found populations at both sideof the mountain ridge(700m) existed genetic differention which is larger than other pairpopulations of Taxus chinensis var. mairei, which indicated the ridge of mountain(700m)related to the genetic differention and hinder the gene flow.更多还原