高原鼢鼠（Myospalax baileyi）分子系统地理学与形态变异研究

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	高原鼢鼠（Myospalax baileyi）分子系统地理学与形态变异研究
其他题名	Molecular Phylogeography and Morphologic Variation of Myospalax baileyi
	唐利洲
学位类型	博士
导师	苏建平
	2009-06-01
学位授予单位	中国科学院西北高原生物研究所
学位授予地点	西北高原生物研究所
关键词	高原鼢鼠线粒体dna 分子系统地理学遗传多样性遗传分化基因流冰期避难所青藏高原隆升第四纪冰期种群历史动态形态变异
摘要	高原鼢鼠（Myospalax baileyi）是青藏高原特有的一种专营地下生活的小型啮齿动物，主要分布于青海、甘肃南部及四川西部的高山草甸、高寒草甸、高山灌丛、农田、浅滩及荒地区域。以往的研究主要集中于对高原鼢鼠分类地位、形态特征、食性、繁殖、行为等宏观生态学的探讨，尽管有线粒体D-loop区标记的研究涉及高原鼢鼠群体遗传多样性及遗传分化，但较少的采样种群并不能完全反映该物种的系统地理格局。迄今为止对高原鼢鼠的种群历史动态变化及分化历史仍缺乏了解，包括种群现有分布格局、历史成因以及种群进化历程和可能存在的冰期避难所。本研究根据线粒体细胞色素b和D-loop区直接测序的序列数据，运用种群遗传学和分子系统地理学方法，分析了187只高原鼢鼠在DNA水平上的遗传多样性、系统地理结构及种群历史动态，探讨了造成地域性种群分化的历史因素，推测该物种的冰期避难所，并通过形态指标多变量比较探究了高原鼢鼠不同地域种群的形态变异。主要研究结果如下： 1．高原鼢鼠的单倍型多样性、核苷酸多样性分别为0.9616±0.0049和0.0531±0.0257。与其它啮齿动物相比，该物种表现出较高的单倍型多样性，而核苷酸多样性很低，这可能与地下稳定生活环境减慢了核苷酸碱基替换速率有关。 2．AMOVA分析结果显示，显著性的多态性变异比例主要分布于群体间（76.3-88.7%）和群内种群间（8.2-20.7%），说明高原鼢鼠存在显著的系统地理结构与遗传分化水平。整个高原鼢鼠种群分化为两个大的血统，即青藏高原内部血统（Clade A）和青藏高原边缘血统（Clade B、C、D和E），五大地域性分支间双向基因流水平很低（Nm=0.03-0.12），表现为分支间平均每一百代仅有3-12只高原鼢鼠的交换，这种限制性的基因流可能与高原鼢鼠独特的地下挖掘取食行为有关。五大地域性分支的分歧时间大致处于0.2-0.9百万年期间，而这段时间正好是第四纪冰期的频发期。内在生物学特性决定的限制性基因流与外在冰期产生的距离隔离、生境片段化，是造成高原鼢鼠地域性种群分化及现有系统地理格局的主要原因。 3．多峰状的错配分布（Mismatch distribution）及为显著正值的Fu’ s Fs检验结果说明，高原鼢鼠群体未经历近期的种群扩张事件；各地域性种群拥有独特的单倍型，分布区域互不重叠。Coalescent模拟分析及验证结果表明，高原鼢鼠在末次盛冰期（Last Glacial Maximum）存在4个冰期避难所，分别对应于四个地域性分化种群所在区域。 4．根据鼢鼠属（Myospalax）大致5-12百万年的化石时间，估计出鼢鼠线粒体细胞色素b基因的平均进化速率为2.434%/百万年/碱基，95%自信区间为1.352-3.493%/百万年/碱基。 5．高原鼢鼠有效种群大小（Ne）对进化时间（Age）的动态分析追溯了33万年以来的种群历史动态。0.33-0.16百万年期间种群波动强度最大，0.16-0.08百万年阶段种群大小基本趋于稳定分布状态，有效种群大小在0.08百万年至今总体呈现缓慢下降趋势，充分证明倒数第二次冰期和末次冰期对高原鼢鼠种群历史产生了重要影响。 6．17项形态测量指标的主成份分析和聚类分析结果一致表明，高原鼢鼠种群存在显著的地域性形态差异，分化产生两个无重叠分布的类群，两个类群呈现出两个不同的分化方向：一个方向表现为头骨较小，顶嵴、额嵴相对分开即颧弓扩张程度小，另一个则为头骨较大，顶嵴和额嵴相对靠拢即颧弓扩张程度大的趋势。
其他摘要	Myospalax baileyi, Qinghai-Tibetan plateau endemic small rodent, strictly adapts to subterranean lifestyle and restricted in the alpine meadows, steppe meadows, alpine shrubs, farmlands, banks and wasteland of the provinces Qinghai, southern Gansu and western Sichuan. Prerious studies mainly focused on discussion about macroscopical ecology, such as the classified status, morphologic character, foraging, reproduction and behavior. Although a study has involved the genetic diversity and divergence by the molecular marker of control region in mitochondrion, lesser sampled populations cannot entirely reflect the phylogeographical pattern of M. baileyi. So far, the population dynamics and diverged history of this species remain unknown, including distribution pattern of current populations, historical reasons, evolutional course and potential refugia in glaciations. Based on sequence data from directly sequencing cytochrome b and control region of mitochondrion, this study revealed the genetic diversity, phylogeographical structure and population dynamics. The history factors affecting population differentiation and potential refugia of this species were investigated. In addition, this study also has explored the morphological variation among different populations of this species based on comparison with multi morphology variables. The main results are summarized as follows: 1. The haplotype diversity and nucleotide diversity of M. baileyi were 0.9616±0.0049 and 0.0531±0.0257, respectively. Compared with other rodents, this species revealed relatively higher level of haplotype diversity, as well as the lower nucleotide diversity, which suggest the stable underground environment might have restricted the nucleotide substitution rate. 2. An AMOVA result revealed that significant proportion of diversity attributable to differences among regions (76.3-88.7%) and among populations within regions (8.2-20.7%). That means significant phylogeographical structure and high levels of genetic divergence within M. baileyi. Two large lineages have diverged from the total population, the Qinghai-Tibetan plateau interior lineage (Clade A) and the Qinghai-Tibetan plateau edge lineage (Clade B, C, D and E). The bidirectional level of gene flow (Nm=0.03-0.12) among the five regional clades, indicated three to twelve individuals exchange occurred at average per one hundred generation. This restricted gene flow may be related to the subterranean behavior of digging and foraging. In addition, the branching age among five regional clades approximately happened at 0.2-0.9 million years ago, which were correspond to the frequent glaciations in the Quaternary. The restricted gene flow from biological traits, distance isolation and fragmented habitats were the main factors for the population differentiation and current phylogeographical pattern. 3. The lack of recent population expansion was supported by the multimodal mismatch distribution and significant positive value of Fu’s Fs within M. baileyi. The regional populations were distributed in separate areas and had the unique haplotypes each other. The result of coalescent simulation and testing from MESQUITE (Version 2.5), combined with the significant phylogeographic structure suggest the existence of four separate glacial refugia during last glaciations. 4. The average mutation rate of 2.434% per million years per site was estimated for the mitochondrial cytochrome b gene of M. baileyi according to the fossil age calibration of genus Myospalax occurred at 5-12 million years. 5. The population dynamics about 0.33 million years have been described as the formal of effective population size through evolution age. The effective population size presented three states of the most intension distribution (0.33-0.16 million years), stable distribution (0.16-0.08 million years) and slow downtrend distribution (0.08 million years to present) at different evolution age. These findings also suggest the population history of M. baileyi might be importantly affected by the penultimate glaciation and the last glaciation. 6. The results of principal component analysis and cluster analysis from seventeen metrical indexes congruously revealed that significant morphological variation among separate populations. The sampled populations were divided into two large regional groups, that is to say, Gansu group and the mixed group including Qinghai and Sichuan populations. These results actually reflected two different directions of evolution: one showed with lesser skull, divided parietal ridges and frontal ridges, such as Gansu group; another showed with biggish skull, closed parietal ridges and frontal ridges, such as the mixed group.
页数	112
语种	中文
文献类型	学位论文
条目标识符	http://210.75.249.4/handle/363003/3224
专题	中国科学院西北高原生物研究所
推荐引用方式 GB/T 7714	唐利洲. 高原鼢鼠（Myospalax baileyi）分子系统地理学与形态变异研究[D]. 西北高原生物研究所. 中国科学院西北高原生物研究所,2009.

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