青藏高原高原鼠兔（Ochotona curzoniae）的进化研究

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	青藏高原高原鼠兔（Ochotona curzoniae）的进化研究
其他题名	Evolution studies of plateau pika (Ochotona curzoniae) on the Qinghai-Tibetan Plateau
	慈海鑫
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	青藏高原高原鼠兔进化体型大小贝格曼规律海拔年温度年降水量年初级净生产力寄生虫感染两性差异年龄差异海拔差异 Mtdna 冰期种群扩张基因流谱系地理结构
摘要	青藏高原是全世界最高的高原，总面积约2.5×106 km2，平均海拔在3000 m以上。自上新世以来，青藏高原历史上经历了高原的强烈隆升和第四纪冰川的发育，彻底改变了高原的整体环境。高原隆升造成了地形的空间异质性，也创造了其他生态环境的异质，为生物进化提供了舞台；而高原上的冷暖气候、冰期间冰期的交替发生，对高原生物的适应辐射、隔离进化和物种形成也产生了重要影响。因此，青藏高原成为研究生物进化的热点地区和理想场所。高原鼠兔（Ochotona curzoniae），又称黑唇鼠兔（black lipped pika），隶属兔形目（Lagomorpha）鼠兔科（Ochotonidae）鼠兔属（Ochotona），是一种植食性小哺乳动物，同时也是青藏高原的特有种和关键种。高原鼠兔地理分布广泛，几乎遍布整个青藏高原。高原鼠兔经历了青藏高原的隆升和第四纪冰川的发育，是研究青藏高原生物进化的理想材料。本论文以高原鼠兔为研究对象，从形态学、生理学、分子生物学、谱系地理学等多个学科方面交叉研究其进化，其主要研究内容和结论如下： 1. 动物体型大小的变化通常与环境条件密切相关。贝格曼规律是反映动物体型大小变化最经典的规律，但对该规律的正确性一直受到人们的怀疑。本研究运用多种数理统计分析方法，研究了高原鼠兔头骨大小的地理变异，验证贝格曼规律及其经典解释的有效性，并对影响高原鼠兔体型大小地理变异的环境因子进行探讨。我们的结果表明，高原鼠兔的体型与纬度和海拔正相关，随着纬度和海拔的升高而逐步变大，遵循贝格曼规律；与年温度、年降水量和年初级净生产力这三个环境因子负相关，随年温度、年降水量和年初级净生产力的降低而体型变大。这与达乌尔鼠兔的研究结果不同，可能是由于高原鼠兔在青藏高原上独特的生态适应策略和适应高原环境压力的特殊生理机制造成的。 2. 在寄生虫感染研究中，寄主性别被认为是一个与寄生虫感染水平相关联的重要因素，它们之间的进化关系已经受到越来越多学者的关注。本研究分析了高原鼠兔体表寄生虫的感染率与寄主性别、年龄以及海拔之间的进化关系。我们的研究结果表明，高原鼠兔体表寄生虫的感染率存在着两性差异、年龄差异和海拔差异：高原鼠兔雌性成体的感染率显著高于雄性；雌雄个体的寄生虫感染率分别随着年龄的增长而上升；雌雄成体尤其是雌性的寄生虫感染率与海拔显著正相关，随着海拔的升高而增加。这可能是由于高原鼠兔荷尔蒙激素、体重、巢区和能量分配在性别、年龄和不同海拔地区中的差异造成的。但是，寄生虫感染率与寄主性别之间的相互关系是一个非常复杂的现象，其季节性变化的研究，应该被进一步开展。 3. 目前，谱系地理学的研究主要集中在伴随着地质历史事件的环境变化对动植物的遗传结构和分布格局的影响。本研究分析了取自青藏高原32个种群的245只高原鼠兔mtDNA的1616 bp片段，包括Cytochrome b （Cyt b）、tRNAThr、tRNAPro和D-loop的高变区（hypervariable domain I, HV I），希望藉此了解高原鼠兔在第四纪冰期气候变迁中的分布变化，以期阐明第四纪冰川发育等重大地质、环境事件对青藏高原地区物种多样性分布格局的影响。我们的研究结果表明，高原鼠兔在历史上经历了快速扩张，种群扩张事件估计发生在0.24～0.03 Mya，这个区间正好位于末次冰期最盛期之前的间冰期。这是因为间冰期内温度上升，冰川消退，给种群的迅速扩张提供了时间和场所，此结果从生物学角度上驳斥了M. Kuhle的“冰盖论”。高原鼠兔不同种群之间存在着从高原边缘种群到高原内部种群的单向性基因流以及高原内部种群之间的双向性基因流。我们推测，这种特殊的基因流类型可能是由于最大冰期和末次冰期对高原鼠兔种群影响的不同程度所造成的。青藏高原最大冰期导致了高原鼠兔内部种群的绝灭，而在那些未被冰川覆盖的高原边缘区域，高原鼠兔又可能幸存下来，从而使这些边缘区域成为最大冰期时的避难所。在间冰期时，伴随着冰川的消退，高原鼠兔从这些处于高原边缘的避难所中逐步向高原内部扩散，形成了明显的单向性基因流。末次冰期时，青藏高原干旱的环境和高日照反射率限制了高原内部冰川的发育。高原鼠兔内部种群在末次冰期避难所中得以幸存，形成了双向性基因流。然而，末次冰期的山谷冰川阻碍了高原鼠兔内部种群与边缘种群之间的基因交流，没有形成反向的基因流。与青藏高原四种土著动物（棕颈雪雀、白腰雪雀、褐背拟地鸦和青海沙蜥）相比，高原鼠兔各种群之间具有中等程度的谱系地理结构。我们认为，高原鼠兔的种群扩张，引发了种群间介于鸟类与爬行类大小之间的基因交流，形成了该类型的谱系结构。
其他摘要	The Qinghai-Tibetan Plateau (QTP) is the highst plateau in the world, with an area of 2.5×106 km2 and with an average elevation more than 3000 m above sea level. Environmental heterogeneity of the QTP had been greatly shaped by the uplifting of plateau since Pliocene and the Quaternary Glaciation. They had great impact on the adaptive radiations, isolation evolution and speciation on the QTP. Therefore, the QTP is becoming a hot area and model region for the research of biological evolution. Plateau pika (Ochotona curzoniae), a member of Lagomorpha orders Ochotonidae family Ochotona genera, is endemic to the QTP. The pika is considered a keystone species in the plateau ecosystem. The distribution of plateau pika largely coincides with the range of the QTP, making it an ideal candidate for understanding the relationships between climate changes and topographic structure and the evolution of species on the plateau. In the dissertation, morphology, physiology, molecular biology and phylogeography of plateau pika were examined. The main contents and research conclusions are as follows: 1. Variability of animal body size often is correlated with environmental conditions. Bergmann’s rule is a classical rule to responding the variation of body size in animal species, but many scientists provide a lively debate on the validity of Bergmann’s rule. In this dissertation, the geographical variation of skull size in plateau pika was studied with advanced statistic analysistic methods. We testified the validity of Bergmann’s rule and its classical explanation and gave the rational interpretations of environmental factors influencing the geographical variation of body size. Our results indicated that skull size was positively correlated with both latitude and altitude, and negatively correlated with annual temperature, annual precipitation, and annual net primary production. These results indicated conformity to Bergmann’s rule in this species. We suggest that, based on the special adaptive strategies of the plateau pika, increasing rather than decreasing body size (as its counterpart, the Daurian pika, does) helps plateau pika survive serious environmental stresses on the QTP. 2. Host sex is considered a significant factor correlated with parasitism levels in the study of parasitism parasitic infections. The evolution relations between host sex and parasitism are attracting increasing attention. In this dissertation, relations between infection rate and host sex, age and altitude were studied in plateau pika. Our results indicated that there is sex-biased, age-biased and altitude-biased parasitism in this species: adult females had significantly higher infection rate than that of males; the parasite infection rates for both males and females increased with increasing age; the parasite infection rates was positively correlated with altitude. We suggested that the differences of hormone, body mass, home range and energy distribution between males and females had mainly caused the biased parasitism of plateau pika. Because the relation between host sex and parasitism is a complex phenomenon, the study of seasonal variation will be continued. 3. At present, most phylogeographical studies have focused on Pleistocene glaciations, which are thought to have had profound impacts on genetic diversification and distribution pattern of the biota. In this dissertation, we studied 1616 bp of mtDNA sequence (Cytochrome b, tRNAThr, tRNAPro, and partial control region) in pika sampled from 32 localities. The study aimed to test the relationship between population history of plateau pika and climatic oscillations in the late Pleistocene, and to study the long-term gene flow of plateau pika. Our results indicated that the population expansion of most groups had occurred 0.24–0.03 Mya, which mostly coincides with the interglacial period before the last glacial maximum (LGM). We suggest that the warmer climate in that period caused degeneration of glacier sheets and thus provided opportunities for population expansion. The result is inconsistent with "Kuhle's hypothesis". Our analysis detected significant unidirectional gene flow from areas around the edges of the QTP towards more central regions and bidirectional gene flow among central regions group. We suggest that this pattern of gene flow reflects the different degrees to which the extensive glacial period (EGP) and the last glacial period (LGP) affected this species. During the EGP, ice cover would have been permanent in the highest altitudes and central regions of the QTP, which would have caused extinction of the central populations. During the interglacial period following the retreat of the EGP glacier, surviving populations in ice-free areas around the edge of the plateau could have expanded towards the interior of the plateau and generated the unidirectional gene flow detected in this study. Although the LGP followed, the very arid conditions and high sublimation rates on the main plateau restricted glacier growth and may have reduced its impact on the central populations. As a result, these central populations apparently survived the LGP and maintained bidirectional gene flow. The LGP conditions, however, did support extensive glacier in the relatively humid areas surrounding the interior of the plateau, and these glaciers might have prevented or greatly reduced the “counter” gene flow from the central populations to more peripheral populations. The phylogeographical pattern of plateau pika differs from the patterns for other QTP endemic species: the red-necked snow finch, the white-rumped snow finch, the ground tit and the lizard. The result showed a moderate level of geographical genetic structure within plateau pika. The moderate level of geographical genetic structure for plateau pika is probably due to the limited dispersal ability of this small mammal.
页数	120
语种	中文
文献类型	学位论文
条目标识符	http://210.75.249.4/handle/363003/3230
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	慈海鑫. 青藏高原高原鼠兔（Ochotona curzoniae）的进化研究[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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