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题名: 南方红豆杉保护遗传学研究
作者: 张雪梅
学位类别: 博士
答辩日期: 2008-01-25
授予单位: 中国科学院昆明植物研究所
授予地点: 昆明植物研究所
导师: 李德铢
关键词: 南方红豆杉 ; 谱系地理学 ; 遗传多样性 ; 遗传结构 ; 保护遗传学
学位专业: 植物学
中文摘要: 珍稀濒危植物南方红豆杉是我国一级保护野生植物。其雌雄异株、风媒传粉、种子通过鸟类或啮齿类动物散布。由于红豆杉属植物中发现的对癌症治疗有特殊疗效的次生代谢产物紫杉醇,导致近十年来红豆杉属植物野生资源的过度采集,致使现存南方红豆杉的野生居群急剧减少,生境已高度片段化。对南方红豆杉进行保护生物学研究迫在眉睫。本文对南方红豆杉进行保护遗传学研究,主要结果与结论如下: 1、谱系地理学研究 通过对南方红豆杉18个居群494个个体的叶绿体基因组的trnL-F片段进行了PCR-RFLP分析,共检测到6个叶绿体DNA单倍型,H1、H2、H3、H4、H5和H6。除了台湾(TW)居群外,所有的居群都包含有单倍型H1和H2;黄山(HSH)居群除H1和H2外还包含单倍型H3;临安(LA)居群除H1和H2还包含单倍型H4。台湾(TW)居群共有两种单倍型H5和H6。谱系关系分析显示单倍型H1、H2为较古老的的祖先单倍型,其它单倍型演化自这两种单倍型。AMOVA分析揭示南方红豆杉仅24.49%的遗传变异存在于居群间,居群内的遗传变异为75.51%。NCA分析揭示现在的遗传结构可能源于居群的片段化效应。台湾为最先分离出去的居群,台湾(TW)居群可能是由于曾经的居群片段化而隔离或长距离扩散所致。居群间的基因流受到一定程度的限制。叶绿体DNA单倍型变化揭示在第四纪冰期,华东地区可能存在南方红豆杉的避难所。 2、基于ISSR的遗传多样性分析 通过对南方红豆杉18个居群494个个体的ISSR研究,揭示了南方红豆杉保持较高水平的遗传多样性,假设处于哈迪-温伯格平衡状态:期望杂和度(HE )为0.3456;Shannon 信息指数(I)为0.5134;有效等位基因数(AE)为1.6047;多态位点百分比(P)为98.4%;居群间的遗传分化系数GST = 0.4079,贝叶斯法的估计值为θB= 0.4854;基因流Nm = 0.7256;近交系数的估计值为f = 0.5066。遗传变异的18.29存在于台湾(TW)居群。UPGMA遗传关系图显示南方红豆杉呈现东西分化的趋势。各遗传参数综合揭示了居群片段化效应。与已报道的其它红豆杉属物种相比较,南方红豆杉保持了较高水平的遗传多样性。 核DNA及叶绿体DNA检测结果均显示现存南方红豆杉的分布可能是由曾经连续分布的南方红豆杉居群片段化而形成,且片段化的过程漫长。避难所居群对现存南方红豆杉的遗传结构依然存在影响,但曾经的大面积连续分布并非由单一的避难所居群扩散而形成,南方红豆杉现在的遗传结构除了植物本身的特点外,受多种因素如多次的片段化过程、分布区的地质历史、避难所、气候及人为干扰等多种因素的影响。 3、种子发芽实验 初步的种子萌发实验显示,在种子苏醒后,红豆杉种子胚乳吸水膨胀使厚厚的种壳开裂,并有少许的绿色,随后即消失。据此,我们初步推断,红豆杉子叶一旦露出胚乳,即与胚乳脱离,基本没有“哺乳期”或者说“哺乳期”非常短,此时幼苗的叶片和根系并不具备完善的功能,幼苗易被灼伤,影响了幼苗的成活率。 4、保护对策 建阳(JY)居群有较高的遗传多样性、较大的群体及合适的年龄结构可作为就地保护的居群。黄山(HSH)、临安(LA)及台湾(TW)居群由于具有其叶绿体DNA具有较高水平的遗传多样性,及独特的单倍型,也应采取就地保护。收集野生居群的种子,通过人工方法提高种子的发芽率,并保证幼苗的成活率,用于增加居群的个体数,特别是对居群内个体间距离相隔较远而年龄结构老化的居群。保护生态环境是提高红豆杉幼苗成活的关键。幼苗的成活为物种不断注入新鲜血液,大量幼苗的成活则可提高遗传多样性,为物种的延续提供基本保障。不同居群间可相互引种从而增加居群间基因的交流。
英文摘要: Taxus wallichiana var. mairei (Lemée & Léveillé) L. K. Fu & Nan Li is a highly endangered conifer. It is dioecious and wind-pollinated, and the seed is dispersed by birds and mammals. It is the source for taxol, an important anti-tumour substance. However, extant natural populations in China are highly scattered due to exceptional loss of habitat and inappropriate harvest of barks of mature trees in the past decade. The research of the conservation biology of it is urgently needed. In this study, some 494 individuals from 18 populations of T. wallichiana var. mairei were collected across the distribution range, including the East China, Central China, and South China mountain floristic regions. 1.Phylogeographic study A total of six haplotypes (H1, H2, H3, H4, H5, H6) were detected in all 494 individuals of 18 populations, in chloroplast DNA trnL-F fragment by PCR-RFLP. H1 and H2 existed in all the populations, but H3 only existed in HSH population, while H4 only existed in LA population, with H5 and H6 coexisting in TW population. The phylogeographic analysis suuggested the H1 and H2 were the ancestor haplotypes, while the others haplotypes were evolved from them. Some 24.49% of the total variation existed among the populations; while 75.51% in the populations suggested by AMOVA. Variation of cpDNA haplotypes suggested a glacial refugium of T. wallichiana var. mairei in the East China region. NCA analysis suggested that the genetic structure of T.wallichiana var mairei resulted from the effect of populaton fragment or the long-distance colonisation. The gene flow was rerestricted. 2. The analysis of genetics diversity base on ISSR The ISSRs revealed a high genetic diversity with PPB = 98.4%, HE = 0.3456, and I = 0.5134 at the species level in 494 individuals of the 18 populations. Population differentiation was low (GST = 0.4079; θB= 0.4854) as was the gene flow among populations (Nm = 0.7256). 18.29% of the total variation existed in TW population suggested by AMOVA. A UPGMA-dendrogram suggests that the population in Taiwan is the most isolated and a trend of east-west split of the populations. The inbreeding coefficient was low (f = 0.5066). The genetic parameters suggested the effect of the fragment, and the gene flow was disturbed. It seems that Taxus wallichiana var. mairei possessed the much high genetic diversity level than the other studied taxa of Taxus Both the detection of nDNA and cpDNA suggested the genetic structure of genetic variation of the extant of T. wallichiana var. mairei was the result of fragmentation of a historically continuous distribution, and the fragmentation process was far-flung. The refugium populations still contribute to the genetic structure of the T. wallichiana var. maire, but the primal metapopulation was not due to the expansion from a single refugium. Beside the feature of T. wallichiana var. mairei per se, the current genetic structure of it was co-effected by the fragmentation of the population, the climate change and the geological history of the distribution ariea and the large-scale habitat destruction caused by human activities. 3. Germination study A preliminary germination test suggested that the endosperm was pale green at the beginning of the seed resurgence. For the species of Taxus, once the cotyledon emerges, it means that the seedling isolates utterly with the endosperms. However, at this stage, the seedlings bear neither functional leaves nor lush root system. Therefore it seems that the seedlings are easy to be burned. This observation is very preliminary and there is no sufficient data in the germination test in the present study. We assume that these characters may have decreased the survival rate of the seedlings in T. wallichiana var. mairei. 4. Conservation stratergy Based on field survey and the results revealed by ISSR markers and chloroplast haplotype variation, together with other evidence, conservation strategy was proposed for the sustainable use of the endangered plant. It is needed to collect seeds from the wild to enhance the germination rate and the survival rate of the germinated seedlings. The seedlings should be used to ensure the size of the disturbed populations. Conservation of the natural habitat is the key to the survival rate of the seedlings. The survival rate of the seedlings is the base of further populations and is the indemnity for the plant to survive. Artificial pollination between populations can increase gene exchanges. Population JY is the largest population of T. wallichiana var. mairei we collected. The population has a reseanable age structure and higher genetic diversity, and therefore is an excellent candidate for in situ conservation. Although the size of populations LA and HSH are small they possess unique cpDNA haplotypes, and may be valuable for in situ conservation, too.
语种: 中文
内容类型: 学位论文
URI标识: http://ir.kib.ac.cn/handle/151853/174
Appears in Collections:昆明植物所硕博研究生毕业学位论文_学位论文

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南方红豆杉保护遗传学研究.张雪梅[d].中国科学院昆明植物研究所,2008.20-25
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