【作者】 王昊；

【导师】 张文驹；

【作者基本信息】 复旦大学 ， 生态学， 2011， 硕士

【摘要】 青藏高原的隆升和第四纪气候变化是高原上生物分布和进化的决定因素。青藏高原的隆升剧烈改变了亚洲的地形和气候,并影响了高原上和邻近地区的生物多样性。然而,青藏高原隆升的过程和时间存在争议,第四纪冰期-间冰期交替对植物遗传分化的影响模式也不确定,使得研究高原隆升对植物的传播、分化和适应的影响仍是一个难题。为了阐明高原上植物进化与高原隆起和第四纪冰期的关系,我们测序了高原上特有植物西藏沙棘(Hippophae tibetana Schlecht.)37个居群891个个体叶绿体DNA的trnT-trnF片段,并测序了外类群中国沙棘、云南沙棘、中亚沙棘、江孜沙棘、肋果沙棘、密毛肋果沙棘和理塘沙棘的个体。在西藏沙棘中研究共得到50种单倍型,并检测到了很强的谱系地理结构。结果表明西藏沙棘单倍型分为三个谱系,分别占据了整个地理分布范围的西部、中部和东部,其分化时间在距今约3.15百万年(Ma)。50种单倍型中,33种是私有单倍型,并散布在西藏沙棘现在的整个地理分布范围中；这些私有单倍型起源于多次分化,并且很多的分化时间在].0 Ma前。这些结果强烈表明在西藏沙棘现在的地理分布范围内,广泛存在着末次冰盛期,甚至是之前几次冰期时的微避难所。此外,在西部的居群平均海拔高于4500米,考虑到末次冰盛期时高原内部的冰川平衡线比现在仅下降500-300米,这意味着很多西藏沙棘末次冰盛期的微避难所海拔在4000米以上,这是目前世界上已知最高的植物避难所。对西藏沙棘三枝谱系之间和内部的分化时间,它们各自独立的分布范围以及造成隔离的气候原因的分析表明,我们的结果支持青藏高原在最近3.4 Ma快速隆升的假说。高原的快速隆升和伴随的环境变化影响了西藏沙棘的传播和分化,塑造了西藏沙棘现在的谱系地理结构。本研究还利用叶绿体trnT-trnF序列和5个微卫星位点研究了在一个具体的微避难所——珠穆朗玛峰北坡绒布河谷里不同海拔西藏沙棘的遗传变异,并整合冰川学、地貌学、第四纪地质学、气象学的资料来研究这一低矮的灌木是如何在此适应过去2万5千年剧烈的气候波动的。微避难所在物种的冰期后扩张中起着至关重要的作用,并且有助于人们理解物种应对现在和未来全球气候变化的响应。然而,学者们仍没有了解植物为什么能在微避难所中避难,以及如何度过冰期时以及冰期之后剧烈的气候波动。本研究的结果表明,绒布河谷是西藏沙棘的一个有很长历史的微避难所；末次冰盛期时西藏沙棘分布在河谷里海拔4800米以下的区域,而在末次冰盛期之后通过在海拔5000米附近的分布范围的上下变化度过了剧烈的气候波动。随着近40年来温度的上升,西藏沙棘的分布上限也已向上迁移了至少30米；并且出乎意料的是,这些新向上扩张的斑块不是来自附近区域,而是来自河谷里海拔最低处的群体。研究结果还表明山坡地形对于西藏沙棘的避难是重要的,同时冰雪和冰川融水也是西藏沙棘生存的关键因素。将种群历史和近期的分布变化相结合,是预测物种在未来气候变化中命运的重要手段。更多还原

【Abstract】 The uplift of the Qinghai-Tibetan Plateau (QTP) and Quaternary climate changes are crucial aspects affecting the distribution and evolution of the plateau biota. The uplift of the QTP dramatically changed the topography and climate of Asia and affected the biodiversity of the plateau and its adjacent areas. However, the effects of the uplift on the dispersal, differentiation and adaptation of plants remain a puzzle when the date and process of the uplift cannot be determined with certainty and the impacts of the alternations of Quaternary glacial-intergalcial on plants on the QTP are unknown. To clarify the relationships among plants on the QTP with the plateau uplift and the Quaternary glaciations, the cpDNA trnT-trnF regions of 891 individuals from 37 populations of Hippophae tibetana Schlecht., endemic to the QTP, were sequenced in the present study, as well as individuals of the outgroup species H. rhamnoides subsp. sinensis, H. rhamnoides subsp. yunnanensis, H. rhamnoides subsp. turkestanica, H. gyantsensis, H. neurocarpa, H. neurocarpa subsp. stellatopilosa and H. litangensis. In H. tibetana, a total of 50 h aplotypes were found and a strong phylogeographic structure was revealed. The results show that three main lineages of the present populations of H. tibetana occupy the western, the middle, and the eastern geographical range, respectively, and their divergence time dates back to 3.15 Ma before present. Of 50 h aplotypes,33 are private haplotypes are scattered throughout the present geographical range of H. tibetana. They originated from multiple differentiations in many lineages during a more than 1.0 M a period, strongly suggesting that multiple microrefugia of H. tibetana existed throughout the present geographical range during the last glacial maximum (LGM) and even earlier glaciations. Additionally, the average elevation of present populations is over 4500 m in the west and the equilibrium-line of glaciers in the LGM was 500-300 m lower than present in the major interior part of the plateau suggesting that at most sites in the west, LGM microrefugia of H. tibetana may have been over 4000 m above sea level, the highest of all known plant refugia. Besides, the divergence times among and within the three lineages and their distinct distributions as well as dispersal barriers support the theory of the recent and rapid uplift of the QTP. The rapid uplift of the plateau within the last 3.4 Ma and the associated environmental changes may have affected the dispersal and differentiation of H .tibetana and shaped its phylogeographic structure. Furthermore, using cpDNA trnT-trnF regions and five microsatellite loci, this study investigated the genetic varations of H. tinetana at different elevations along Rongbuk valley, north of Mt. Everest, which is one of the LGM microrefugia, and by integrating geological, glaciological and meteorological information, to study how the low shrub has adapted to the extreme climate fluctuations of the last 25,000 years. Microrefugia are thought to play an important role in the post-glacial colonization of species, and are pertinent to understanding how species might respond to recent and future climate changes. But why species could survive in such microrefugia and how they responded to climate changes in the glacial and post-glacial periods remain unclear. The results show that Rongbuk Valley was a microrefugium of H. tibetana with a long history, and that H. tibetana survived below 4800 m during the LGM and survived the extreme climate fluctuations after the LGM by upward and downward migrations at around～5000 m. Moreover, with the rise of temperature in the last four decades, the upper limit of H. tibetana has shifted at least 30 m upward; surprisingly, these new arrivals did not expand from adjacent areas but from populations near the lower altitudinal limit. Our results demonstrate that not only did mountain slopes play an important part in H. tibetana finding refuges, but that ice and glacial meltwater were also critical for its survival. Combining population history and recent range shifts of this species is important in predicting the fate of this species to future climate changes.更多还原