【作者】 毛康珊；

【导师】 刘建全；

【作者基本信息】 兰州大学 ， 生态学， 2010， 博士

【摘要】 大陆板块运动是造就现存生物分布格局的主要原因。板块构造运动通过改变各个大陆之间的联系、(改变大气环流和洋流循环进而间接地)改变全球气候等,塑造了各大陆生物的分布格局。广义柏科全球广布并且化石记录丰富,是验证大陆板块构造历史的理想材料。该科刺柏属间断分布于北半球,是研究北半球植物区系演化历史以及验证北半球陆桥迁移扩散学说的理想类群。此外,该属西藏圆柏复合体分布于青藏高原南部和东部,是研究高海拔地区物种谱系地理学和冰期后种群重建历史的最佳对象。本文从三个不同的分类学等级(即：科、属、种)以及与之分别相应的三个不同时间尺度上,对柏科植物的生物地理学进行研究。第一,测定了柏科所有属、超过80%物种的5套叶绿体片段DNA序列,并通过多种分析方法,重新确立了该科的生物地理学历史和物种分化历史。结果表明该科起源于三叠纪末期并于侏罗纪中期开始分化,到白垩纪早期时所有亚科便已经全部确立：柏科起源于“泛古陆”,并随着该古陆的逐渐破碎、分离,形成现有的分布格局；澳洲柏亚科、狭义柏木亚科目前分别分布于南、北半球,二者大致在白垩纪早期中段(125.88±6.89百万年前)分化开来。本项工作具有广泛的生物地理学意义,古生物或广布类群地理分布格局形成机制等相关研究或将从中受益。第二,测定了刺柏属四分之三物种的9套叶绿体片段DNA序列,并通过多种分析方法,确立了该属的生物地理学历史和物种分化历史。刺柏属可能起源于古地中海植被,并且在始新世晚期、中新世中期和上新世时,自欧亚大陆往北美洲迁移过三次；在渐新世晚期时往非洲迁移一次。该属分化速率在渐新世有所减缓,但是从中新世开始,又大幅加快,产生了该属现存的大部分物种。本项工作为往后(古加利福尼亚-)古地中海植被相关研究提供了一个详尽的范例。第三,测定了青藏高原西藏圆柏复合体(刺柏属圆柏亚属)102个种群、590个个体、3个叶绿体片段DNA序列,并通过多种分析方法,确立了该复合体物种的谱系地理学历史。该复合体的种群间分化大(GST=0.49,NST=0.72),存在明显的谱系地理结构(NST>GST，P<0.01),且种群间的基因流较小在检测到的62种单倍型中,40种单倍型为(特定种群)特有单倍型(?)这些特有单倍型以及总体遗传多样性都均匀地分布在青藏高原台面和边缘的种群中,强有力地证明了在最后一次大冰期时该复合体现有分布范围内存在多个微型避难所,而且有些微型避难所存在于3500米海拔以上的区域。本项工作极大的完善了原有的避难所学说,并将引发更多关于高山地区微型避难所的研究。更多还原

【Abstract】 Plate tectonics has greatly impacted the distribution and migration of biota on different continents by changing connectivity between them; it has thus shaped the current biogeographic pattern. Nearly all current continents were united together as the single one, known as the supercontinent "Pangea" during the latest Paleozoic and the early Mesozoic. From the Jurassic on, the northern and southern part of this supercontinent began to drift apart and form two new supercontinents; of which, Laurasia was in the north and mostly comprised the northern hemisphere continents, while Gondwana in the south consisted of the southern hemisphere continents. Laurasia started to break up into plates that gave rise to the current Eurasia and North American since the Jurassic, while Gondwana was gradually disassembled into plates that became the present Africa, South America, Antarctic. Australia and India etc. When two such landmasses separated, biota inhabiting each one began to evolve in different directions, which is the basis of the "Vicariance" theory in the biogeographic studies. Plate tectonics might also change the circulation of atmosphere and ocean currents, which could in turn lead to paleoclimate changes; and through the later, plate tectonics indirectly affected the biogeographic pattern of each continent. In addition, climate oscillations during the Quaternary influenced the distribution pattern of the current biota, especially at the species level. Generally. it is hypothesized that when paleoclimate was warmer, e.g. during interglacial periods, species tended to colonize or move towards high latitude regions or high attitude habitats; and when climate was cooler, e.g. during glacial maxima, these species retreated to lower latitudes and altitudes:glacial refugia provide an example of this.Cupressaceae sensu lato (comprising 32 genera and about 160 species) is of cosmopolitan distribution and its fossil record is long and abundant. This family is ideal for testing biogeographic hypothesis related to vicariance due to paleo-tectonics. As the biggest genus of this family, Juniperus contains 67 species disjuctly distributed in the Northern Hemisphere. The biogeographic history of this genus may be highly correlated with migrations and dispersals of plants through the Land bridges in the Northern Hemisphere. In addition, some species of this genus are distributed in the high altitude regions, for example, the Qinghai-Tibet Plateau (QTP) which was suggested to have experienced extensive glaciation and climate changes during the Quatenary. These species are good models for studying the phylogeographic history on the QTP. In this study, we aimed to study biogeographic patterns of members of Cupressaceae on three different taxonomic levels (family, genus and species) and also at different timescales from the Cretaceous to the Quaternary.First, the biogeographic and diversification histories of the whole family were constructed, Phylogenetic relationships within the Cupressaceae were constructed using 5 cpDNA regions and the diversification history of this family was dated by relaxed molecular clock approach with multiple calibrations. By employing ancestral distribution area reconstruction analysis, a biogeographic history of Cupressaceae was inferred together with fossil records. Cupressaceae and "Taxadoids" (includes Taxaceae, Cephalotaxus) diverged with each other around the Permian/Jurassic boundary. The subfamily Cunninghamioideae split from the other members of Cupressaceae since the middle Jurassic, followed by the subfamily Taiwanioideae, Athrotaxioideae, Sequoioideae and Taxodioideae during the middle to late Jurassic, the late Jurassic, the Jurassic/Cretaceous boundary and the early Cretaceous, respectively. The remaining lineage diverged into the subfamily Cupressoideae (Rich. ex Sweet) and Callitroideae (Saxton) during the middle Early Cretaceous. This vicariance between the monophyletic Cupressioideae (Northern Hemisphere) and Callitroideae (Southern Hemisphere) was estimated to have occurred during the middle Early Cretaceous (125.88±6.89 million yeas ago), which is highly consistent with these new geological evidences for separation betwen Gondwana and Laurasia. The present first independent estimation has a general significance for understanding vicarient patterns of other organisms between the current continents during the Cretaceous.Second, the biogeographic and diversification history of Juniperus was examined in detail. Nine cpDNA fragments (>10000bp) from 51 Juniperus species were determined and phylogenetic relationships were constructed. The diversification timescales of Juniperus were generated by employing three relaxed molecular clock approaches with 8 calibration points. Then, the biogeographic history of this genus was infered based on Bayes-DIVA analysis and fossil records. Juniperus and Cupressus s. lat. are both monophyletic and they diverged with each other around the Cretaceous/Tertiary boundary. Juniperus may have had a wider distribution range including Europe and Asia during the early Tertiary:and it began to diversify into seven lineages and dispersed all over the Northern Hemisphere during the period from the late Eocene to the early Oligocene. Three migrations of junipers from Eurasia to North America were detected; these occurred during the late Eocene, the middle Miocene and the Pliocene, respectively. The only juniper species (J. procera) occurring south of the equator probably migrated from Eurasia to Africa during the late Oligocene. The diversification of this genus was slow during the Oligocene, but since the Middle Miocene, its diversification was accelarated, generating most of the current species. Juniperus species probably comprised a part of the Madrean-Tethyan vegetation that strentched from California (Madrean) to Mediterranean (Tethyan) during the early to middle Tertiary (Paleocene, Eocene and Oligocene). This study provides a detailed example of how one genus in this vegetation belt diversified and migrated.Third, the phylogeographic history of the Juniperus tibetica complex from the Qinghai-Tibet Plateau was studied. Three cpDNA regionsfor 590 individuals from 102 populations of this complex were sequenced. Significant interpopulation differentiation as well as phylogeographic structure were detected (GST= 0.49, NST= 0.72, NST> GST, P< 0.01), indicating limited gene flow among populations. Of 62 haplotypes,40 were restricted to single populations. These private haplotypes and overall degrees of diversity were evenly spread among plateau and edge populations, providing strong evidences for the existence of numerous Last Glacial Maximum (LGM) microrefugia throughout the present distribution range of this complex, most of which were located above 3500 m. These results mark the highest known LGM tree lines, illustrating the potential significance of the high-mountain areas for the glacial refugia. More researches on alpine microrefugia may be triggered by this study.更多还原