密叶红豆杉的种级界定和保护遗传学研究
其他题名Species Delimitation and Conservation Genetics of Taxus fuana Nan Li & R.R. Mill (Taxaceae) in Pakistan
MuhammadAminUllahShahAmin
学位类型博士
导师李德铢
2007-05-30
学位授予单位中国科学院昆明植物研究所
学位授予地点昆明植物研究所
学位专业植物学
关键词密叶红豆杉 物种界定 保护遗传学 谱系地理 遗传多样性 遗传分化 保护策略
摘要密叶红豆杉是西喜马拉雅地区特有的濒危物种,且红豆杉的分类在西喜马拉雅地区一直比较混乱。本文对分布于西喜马拉雅地区的须弥红豆杉、欧洲红豆杉和密叶红豆杉进行了研究,通过对62份蜡叶标本的27个形态学性状的主成份分析及核基因ITS和叶绿体基因trnL-F的序列分析,结果表明三个种形成不同的分支,支持各自为独立的种,组合的形态性状可做为区分三个种可靠的鉴别特征。分布于西喜马拉雅地区的红豆杉为密叶红豆杉,其种级地位得到形态学和分子证据的强烈支持,并对三个种的分布区进行了重新的界定。 RAPD数据的遗传学分析表明,密叶红豆杉居群内的遗传多样性较低,而居群间存在较高的遗传变异。这样的结果可能是由于密叶红豆杉的生境的片断化和进化历史,如遗传漂变和有限的基因流所导致。在此结果的基础上对密叶红豆杉的就地保护和迁地保护的策略进行了讨论。 利用DPS和PCA对密叶红豆杉的形态学性状进行了分析,结果表明这些性状受生态因子的影响较大。Mantel 检测显示欧式距离与地理距离间存在一定程度的相关性,而居群间的遗传距离与欧式距离间无相关性。 在谱系地理研究中发现了2个单倍型,单倍型I分布最广,存在于所有的居群中,而单倍型II仅发现于居群SW中的单一个体中。由于检测到的单倍型有限,密叶红豆杉的谱系地理关系没有得到很好的解决,还需要进一步的深入研究。
其他摘要Taxus fuana Na Li & R. R. Mill, an endangered species, is endemic to the Western Himalayas. Recent deforestation and overexploitation have driven numerous wild populations of the species into the extinction, and surviving populations are rapidly declining in size. The extent and distribution of genetic variation within a species is of fundamental importance to understand its evolutionary potential, and thus determine its survival. Assessment of genetic variation within endangered populations is perquisite for effective conservation strategies. The nomenclature and taxonomic status of Taxus in the Western Himalayas has long been problematic. Twenty-seven morphological characters, 62 selected herbarium specimens of T. wallichiana, T. baccata and tentatively identified T. fuana were used to investigate the taxonomic status of Taxus in Pakistan by means of principal component analysis (PCA). Three discrete clusters representing the three species were observed in the PCA scatter plots. Character combinations allowed reliable identification of specimens of T. wallichiana, T. baccata and T. fuana, while sequence data of nrDNA ITS and the chloroplast trnL-F region were used to further delimit T. wallichiana, T. baccata and T. fuana. Using maximum parsimony analysis three distinct clades were obtained representing the three species. Based on both morphological and molecular data, the Taxus species occurring in the Western Himalayas including Pakistan was shown to be T. fuana and not T. wallichiana or T. baccata. Levels of genetic variation and pattern of population structure within and among 10 wild T. fuana populations from Pakistan were investigated. The results showed that there is a low level of genetic diversity within population and a significant genetic differentiation among populations was detected (ΦST = 0.5685). The gene flow was low with an estimate of Nm = 0.3558. As a consequence of habitat fragmentation, evolutionary factors including genetic drift and limited gene flow may be responsible for the above-mentioned findings. Based on these findings, conservation concerns are discussed together with possible strategies for implementing in situ and ex situ conservation. The morphological characters were analyzed by using data processing system (DPS) and principal component analysis (PCA). The results indicated that continuous characters were significantly determined by ecological factors. No significant correlation between genetic distance and Euclidean distance was present. While there is correlation between Euclidean distances and geographical distances by Mantel test in the 10 sampled populations of T. fuana. No correlation between the morphological and molecular data was found. Of 12 regions of chloroplast DNA screened by using nine restriction enzymes with PCR-RFLP, in only one region (trnL-F) was a usable polymorphism detected. Only two PCR-RFLP haplotypes were distinguished in the 10 populations. Haplotype 1 was widespread and fixed in all sampled populations, while the private haplotype 2 was detected in a single individual of population SW. Haplotype 2 might be derived from Haplotype 1 by two mutational steps. No phylogeographic pattern in T. fuana in Pakistan was resolved due to limited haplotypes detected in the present study. The chloroplast DNA variation of T. fuana was much lower than that of other gymnosperm species, which possibly resulted from its evolutionary history.
页数108
语种中文
文献类型学位论文
条目标识符http://ir.kib.ac.cn/handle/151853/238
专题昆明植物所硕博研究生毕业学位论文
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MuhammadAminUllahShahAmin. 密叶红豆杉的种级界定和保护遗传学研究[D]. 昆明植物研究所. 中国科学院昆明植物研究所,2007.
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