Biogeography and molecular phylogeny of the genus Schizothorax (Teleostei : Cyprinidae) in China inferred from cytochrome b sequences

Aim: To test a vicariant speciation hypothesis derived from geological evidence of large-scale changes in drainage patterns in the late Miocene that affected the drainages in the south-eastern Tibetan Plateau. Location: The Tibetan Plateau and adjacent areas. Methods: The cytochrome b DNA sequences of 30 species of the genus Schizothorax from nine different river systems were analysed. These DNA sequences were analysed using parsimony, maximum likelihood and Bayesian methods. The approximately unbiased and Shimodaira-Hasegawa tests were applied to evaluate the statistical significance of the shortest trees relative to alternative hypotheses. Dates of divergences between lineages were estimated using the nonparametric rate smoothing method, and confidence intervals of dates were obtained by parametric bootstrapping. Results: The phylogenetic relationships recovered from molecular data were inconsistent with traditional taxonomy, but apparently reflected geographical associations with rivers. Within the genus Schizothorax, we observed a divergence between the lineages from the Irrawaddy-Lhuit and Tsangpo-Parlung rivers, and tentatively dated this vicariant event back to the late Miocene (7.3-6.8 Ma). We also observed approximately simultaneous geographical splits within drainages of the south-eastern Tibetan Plateau, the Irrawaddy, the Yangtze and the Mekong-Salween rivers in the late Miocene (7.1-6.2 Ma). Main conclusions: Our molecular evidence tentatively highlights the importance of palaeoriver connections and the uplift of the Tibetan Plateau in understanding the evolution of the genus Schizothorax. Molecular estimates of divergence times allowed us to date these vicariant scenarios back to the late Miocene, which agrees with geological suggestions for the separation of these drainages caused by tectonic uplift in south-eastern Tibet. Our results indicated the substantial role of vicariant-based speciation in shaping the current distribution pattern of the genus Schizothorax.

青藏高原东部混农季节性放牧及其对高山林线格局的影响

混农季节性放牧（agropastoral transhumance）通过作物种植和畜牧生产相结合的方式对不同海拔高度带上的资源进行相互补充利用，在亚洲兴都库什地区、青藏高原、横断山、东部及南部非洲、南美安第斯地区等具有悠久的历史。这种传统的生计系统几千年以来一直是居住在该地区的人类社会和自然生态系统相互作用的主要形式之一。这种传统的资源利用方式与山地自然植被以及特殊的山地人类文化和社会特征具有密切的协同演变关系。认识和理解这一关系，是山地生态学和人类学的核心科学问题之一。近年来，山地生态系统的多重功能性及动态演变对山区社会经济可持续发展的重要意义受到人们的不断关注。本文通过对云南省德钦县的12个自然村的混农季节性放牧以及对云南德钦、四川壤塘等山地植被格局特别是高海拔地带植被格局的的详细调查，探讨青藏高原东缘地区混农季节性放牧的主要特征、系统构成及相互关系，及其在全球变化、经济全球化和市场化及现代化过程中的变化趋势，分析混农季节性放牧与高山林线格局及生态系统的互动关系，旨在探讨山地地区人类活动与自然生态系统之间的互动关系，从而为山区社会经济可持续发展、环境建设和生物多样性保护等国家战略提供理论依据。 调查结果表明，混农季节性放牧是一种适应青藏高原东部高山峡谷地区环境因子及自然资源呈明显的垂直分布、资源数量稀少而时空分布异质性极高的生存环境的一种传统经济形式。这种传统的畜牧业的主要生产目的仍然是提供当地基本生存所需的产品，饲养牲口的种类和数量取决于农户的当地需求并且受资源的限制，因而维持在比较低的水平的。分布在不同海拔高度的放牧资源在一年中被牲口利用的时间也不同，互为补充，共同构成混农季节性放牧的资源基础。根据各社区永久居住点的位置和该村的土地资源特别是牧草地资源的分布范围，牲口迁移的距离和格局有较大的差异。。天然牧场仍然是最主要的畜牧业生产资源。混农季节性放牧中的农业系统和牧业系统互为补充，共同构成调查地区完整的的生计系统，农耕活动为放牧活动提供精饲料如粮食等和冬季饲料如秸秆， 其数量往往成为家庭畜牧业生产规模的主要决定因子之一。 通过对牲口数量和结构、牲口的时空迁移格局、牧业活动在整个经济活动中的相对重要性以及牧业活动和作物种植的关系方面的研究分析，混农季节性放牧在近几十年发生了深刻的变化。主要表现在牲口数量总体下降，牲口组成发生变化，牲口移动性降低、牧业活动的经济重要性下降以及牧业活动和种植活动之间的相互依存度降低等。上述变化的根本驱动力是发生在当地、地区及全球尺度上的环境、政治、社会经济、技术和文化等的变化，从而造成当地群众畜牧生产目标、土地利用和劳动力的分布等发生了变化。当地生计系统发生的改变可能会带来对方面而深刻的政治、社会经济、文化和生态影响。 混农季节性放牧这种古老的传统生计策略面临着许多挑战，如冬季饲料短缺、草场退化、缺乏市场竞争力、经济重要性降低、对年轻人缺乏吸引力、国家缺乏专门的政策指导等。与此同时，经济全球化、市场经济、新技术的应用、替代生计机会的增加、国家对于山地生态系统的作用的重新定位等也为传统生计系统转型、实现社会与生态共赢创造了机遇。 混农季节性放牧活动对亚高山及树线交错带生态系统系统的互动方式主要体现在以下几个方面：（1）牲口啃食、践踏等影响森林群落更新，改变森林群落的组成和结构，从而影响森林群落的演替进程和植被格局。林线边缘是搭建夏棚的首选地点，因此林线及树线交错地带就成了牲口活动的主要场所之一；（2）利用火烧开辟、维持和改良高山牧场； 3）在亚高山火灾迹地的放牧活动能够阻止火烧迹地的顺向演替； 4）牧民在林线附近获取建材和薪材等活动影响高山林线附近森林的结构和功能。 在调查区域，梅里雪山、白马雪山、甲午雪山的林线海拔高度在4200-4300m之间； 四川雅江、理塘一线，林线位置多在4300-4400m；四川壤塘二林场一带的林线主体在4100-4200m，在个别地区达到4300m； 在贡嘎山的南坡和东坡一带，林线位置在3600-3700m；而在四川松潘一带，林线位置主体在3700-3800米左右。树线高度的分布趋势和林线一致。混农季节性放牧及其有关人类利用活动使研究地区很多地方高山林线降低、树线交错带宽变窄或消失。在研究地区，总体情况是，阳坡和半阳坡（南坡、西南坡等）的林线和树线比阴坡和半阴坡（北坡、东北坡等）低，变化幅度达20-200m。这种差异主要是为了开辟牧场而人为清除了南向坡自然林线及其以上的植被从而使林线位置下降所致。在南坡自然林线保留得比较好的地方，林线和树线依然可以达到甚至超过北坡林线和树线的高度。放牧活动抑制了高山林线带火烧迹地的天然更新，从而使林线位置保持在目前的位置。 放牧活动对高山林线带森林群落更新的影响是显著的。自然林线内的乔木个体密度特别是新生苗和幼苗的密度大大高于非自然林线。没有放牧的自然林线及树线交错带内的I级个体（新生苗）密度达到725-2917株/公顷，而与之相对的处理样地内I级个体的密度只有0-228株/公顷；II级个体（高度10-50cm）也表现出类似的趋势，在没有放牧的自然林线及树线交错带样方内，其密度达到550-5208株/，而在放牧处理样方内只有14-321株/公顷。在非自然林线带样地内，在有正常放牧的样地内，完全缺乏I级个体。 从相对比例来看，没有放牧的样方内的I、II级个体在全部个体中所占的比例显著高于有放牧活动的样方。放牧使林线交错带的乔木幼苗数量显著减少，从而影响林线及树线交错带森林群落的天然更新过程。林线和树线交错带的灌木对乔木幼苗具有重要的保护作用，能够为树线树种如冷杉等幼苗的定居体提供有利的微气候环境，同时保护苗免受牲口的啃食和践踏。火烧以后接着进行放牧能够100%地抑制高山林线带的幼苗更新。 高山牧场放牧强度降低、使用时间缩短而低海拔地带放牧强度增加是研究地区混农季节性放牧系统的一个显著变化。这种变化也必然会引起各海拔带上的生态系统的变化。放牧强度的降低、生产性用火的停止将导致原来通过人工火烧而降低并通过进一步的火烧和放牧活动来维持的林线及其以上地带的灌木盖度和高度的增加，从而为林线森林群落的扩张创造条件。 青藏高原东部高山峡谷地区是我国重要的山地生态系统，在我国的生物多样性保护、生态环境建设、社会经济可持续发展战略中具有举足轻重的作用。正确认识人类特别是当地传统的生计系统与生态环境系统的互动关系是实现上述战略目标的前提。决策者必须以综合、系统的的视角协调促进社会经济可持续发展、保护生物及文化多样性和维持人、牲口和生态系统之间的平衡的多重目标。 Agropastoral transhumance, which makes a complementary exploitation of the natural resources at different altitudinal belts through a combination of migratory animal husbandry and crop cultivation, has a long history in Hindu-Kush Himalaya, Tibet Plateau, Hengduan Ranges, eastern and southern Africa and the Andes region of south America.For millennia, this traditional livelihood strategy has been one of the main forms of interaction between human societies inhabiting in these regions and their natural ecocystems. A close co-evolutionary relationship has been developed between this indigenous resources management systems and the mountain vegetation systems on the one hand and a unique set of cultural values and social features on the other. Understanding this relationship has been one of the core scientific issues in mountain ecology and anthropology. In recent years, the importance of the multiple functions of the mountain ecosystems and their dynamic changes in the sustainable socio-economic development of the mountain regions has gained increasing attention. This paper, which is based on a detailed study on the agropastoral practices of the 12 natural villages in Deqin County of Yunnan, and the mountainnn vegetation patterns in Deqin of Yunnan and Rangtang County of Sichuan, intends to reveal the major characteristics, system composition and the inter-relations of the subsystems of the agropastoral transhumance in Eastern Tibetan Plateau as well as the trends of changes of the system within the context of global changes, economic globalization and modernity process of China and analyze the relations between agropastoral transhumance and alpine ecosystem, ao as to understand the interactions between human activities and natural ecosystems of the mountains and provide theoretical basis for the national strategies in eocioeconomic development, environmental reconstruction and biodiversity conservation in the mountain regions. Results of the survey indicate that agropastoral transhumance in the investigated area is a traditional economic form that is highly adapted to the eastern Tibet Plateau where the topography features high peaks and deep gorges and where the highly variable environmental parameters and scanty natural resources exhibit a distinct vertical spectrum of distribution and great temporal and spatial heterogeneity. The main objective of pastoral management is still aimed at the production of basic goods and services of local people and thus the type and size of animals raised for each household mainly depend on local needs and are limited by the availability of natural resources. The scale of production is relatively low. Pastoral resources at different altidudinal belts are complementarily used at different seasons of a year and thus form the resources basis for agropastoral production of the study area. Migration distances and patterns vary with the location of the permanent settlements, the elevational distribution range of the resources of the villages concerned. Natural pastures (rangelands) are the main fodder resources and sumplement feedings only account for less than 5% of the total fodder consumption. Crop cultivation and pastoral activities support each other to form a complete livelihood system. The ability of the farmig lands (crop cultivation) to provide the pastoral activities with concentrates and sumplements often becomes a main factor limiting the scale of livestock production at household level. Agropastoral transhumance is experiencing drastic changes in recent decades as is reflected in the size and composition of animals, the seasonal migration pattern, the relative importance of pastoralism in the household economy and the interplays of agricultural and pastoral elements of the system. In general, there is a decline in animal population and mobility, a shift in animal composition to meet new needs arising from changed macro-economic situation, a decrease in the relative importance in the household economy and an increasing decoupling of agro&pastoral relations. The fundamental divers of these changes can be traced to environmental, social, economic, technological and cultural changes from local to global levels and such changes have further caused local changes in livestock management objectives, land use and distribution of labor forces. Changes in local livelihood systems could have profound political, socioeconomic, cultural and ecological conseuquences. Agropastoral transhumance, as an age-old traditional livelihood strategy, is facing multifacet challenges, such as winter fodder shortage, rangeland degradation, lack of market competitiveness, decrease in economic importance, lack of appreciation among the young generation and adequate policies from the government. At the same time, economic globalization, market economy, intrdoctution of new technologies, increase of alternative income generating opportunities and the national re-oreitation of policies on mountain ecosystems have all brought about new opportunities for the transformation of the traditional livelihood system and the synchronized development of local society and the environment. Agropastoral transhumance interacts with the ecosystems at the timberline and treeline ecotone mainly through the following aspects: 1)Animal browsing and stamping affect the regeneration process of the forest communities and alters the composition and structure of the forest which in turn affect the succession process and vegetation pattern of the forest communities. Forest edges are the priority locations for summer houses and therefore the timeline and treeline area becomes the major venues of aninal activities; （2）herders create, maintain and improve pastures through burning that remove the forest communities at the timeline and treeline ecotone; 3）immediate grazing on the fire sites can significantly prevent the fire sites from perogressive succession; and 4）herders harvesting of construction timber and firewoods affects the structure and functions of the forest communities at the timberline and treeline zone. Timberline position in the survey region shows geographical variations. It is around 4200-4300m in Meilixueshan, Baimaxueshan and Jiawuxueshan in Northwest of Yunnan and rises to 4300-4400m in Yajiang County and Litang County of Sichuan. In Rangtang of Sichuan, it is between 4100-4200m, though reaching 4300m in localized sites. In the southern and eastern slopes of Gongga Mountain, the timberline is only between 3600m and 3700m and in Songpan County at the upper reach of the Minjiang River the timberline is around 3700-3800m.Treeline pattern follows similar trend. In many places, agropastoral transhumance and related human activities have lowered the timberline and treeline and narrowed or removed the treeline ecotone. In the area of survey, generally speaking, timberlines and treelines are lower on the southern slopes than on the northern slopes, with a difference between 20 and 200m. This is mainly because that the use of fires to crerate pastures has removed the forest vegetation at the previous timberline and above. In fact, in many places, well-preserved forests on the south slopes have even high timberline position that the corresponding northern slopes. At subalpine zone, grazing activities could have prohibited the natural regeneration of many forest fire sites and maintained the forest position at the present level. Grazing has a significant impact on the regernation process of forest communities at the timberline zone. Natural timberline and treeline ecotone has much higher density of treeline species individuals especially the emergents and seedlings than the timberlines that are maintained by human activities. In natural timberline and treelien ecotone without grazing interference, the density of the I Class seedlings (less than 10cm in height) ranges 725-2917 /hm2; while that in the treatment plots (with grazing disturbance) is only 0-228//hm2；II Class seedlings (10-50cm）exhibit similar density trends, reaching 550-5208//hm2 in natural timberline without grazing but only 14-321//hm2 in the plots with grazing treatment. In the man-created timberlines, there is no I Class seedling at all in plots with normal grazing activities. In relative terms, in plots without grazing activities, the propotion of I Class and II Class seedlings is much higher than that in plots with grazing. Grazing activities have significantly reduced the number of seedlings in the timberline ane treeline ecotone, and thus affect the natural regeneration process of the forests. Shrubs at the timberline and treeline ecotone can effectively protect the seedlings from severe climate and animal tramping, thus increasing the survival rate of the seedlings. Grazing following fires can completely inhibit forest regeneration process at timberline. Changes in agropastoral transhumance will have great impact on the timberline and treeline pattern of the studied area. The decrease in grazing intensity on alpine pastrues and the cessation of the use of fires will result an increase in the cover and height of shrubs above the present human-maintained treeline, which will create further condition for the expansion of timberline forest communities. Eastern Tibet Plateau harbors some most important mountain ecosystems of China that are of vital importance to the country’s strategy in biodiversity conservation, environmental construction and sustainable sociaoeconomic development. A proper knowledge of the interactions between traditional livelihood systems and the ecosystems in the region is a precondition to the realization of the above strategic goals. Therefore, the decision-makers must have a holistic and systemic perspective so as to integrate the multiple objectives of promoting sustainable socioeconomic development, conserving biological and cultural diversity and maintaining the balances among people, animal population and the ecosystems.

青藏高原东部长周期大地电磁测深研究

As a complement to conventional MT, Long-period Magnetotellurics (LMT) has been developed at low frequency for soundings of deep electric structures. Eastern Himalayan Syntaxis (EHS) and surrounding area is a key place for the study of dynamics of the uplift of Tibetan plateau. Experiments in the pioneer studies for EHS3D project showed that the study area shares an unusual low resistive crust and upper mantle. Conventional MT could not provide sufficient information about the deep structures of the study area that requested long period MT measurement to be complemented. This thesis presents the LMT studies in eastern Tibet along the EHS3D-3 Profile from Xiachayu to Yushu including data acquisition, processing, inversion and interpretation. The effective period of the measured LMT signals extend from 10s up to 30000s for the duration more than one week measurement. The resulting model shows that the LMT sounding coincides with the MT data in overlapped periods. Especially the induction arrows and tippers derived from LMT data provide more information about the base of the conductors beneath the plateau with higher resolution. Anomalous induction coefficients and 2-D model suggest extensive conductive bodies beneath Lhasa block and Qiangtang terrain which would be a possible evidence for partial melt and fluids at depth.

东喜马拉雅构造结新生代碰撞变形与岩石圈演化

The Eastern Himalayan Syntaxis (EHS) is one of the strongest deformation area along the Himalayan belt resulted from the collision between Indian plate and the Eurasian Plate since the 50～60Ma, and has sensitivity tracked and preserved the whole collisional processes. It should depend on the detail geological investigations to establish the deformational accommodate mode, and the uplift history, to elucidate the deep structure and the crust-mantle interaction of the Tibet Plateau of the EHS. The deep-seated (Main Mantle Thrusts) structures were exhumed in the EHS. The MMT juxtapose the Gangdese metamorphic basement and some relic of Gangdese mantle on the high Himalayan crystalline series. The Namjagbawa group which is 1200～1500Ma dated by U/Pb age of zircon and the Namla group which is 550Ma dated by U/Pb age of zircon is belong to High Himalayan crystalline series and Gangdese basement respectively. There is some ophiolitic relic along the MMT, such as metamorphic ocean mantle peridotite and metamorphic tholeiite of the upper part of ocean-crust. The metamorphic ocean mantle peridotites (spinel-orthopyroxene peridotite) show U type REE patterns. The ~(87)Sr/~(86)Sr ratios were, 0.709314～0.720788, and the ~(143)Nd/~(144)Nd ratios were 0.512073～0.512395, plotting in the forth quadrant on the ~(87)Sr/~(86)Sr-~(143)Nd/~(144)Nd isotope diagram. Some metamorphic basalt (garnet amphibolite) enclosures have been found in the HP garnet-kynite granulite. The garnet amphibolites can be divided two groups, the first group is deplete of LREE, and the second group is flat or rich LREE, and their ~(87)Sr/~(86)Sr, ~(143)Nd/~(144)Nd ratios were 0.70563～0.705381 and 0.512468～0.51263 respectively. Trace element and isotopic characteristics of the garnet amphibolites display that they formed in the E-MORB environment. Some phlogolite amphibole harzburgites, which exhibit extensive replacement by Phl, Amp, Tc and Dol etc, were exhumed along the MMT. The Phl-Amp harzburgites are rich in LREE and LILE, such as Rb, K etc, and depletes Eu (Eu~* = 0.36 ～ 0.68) and HFSE, such as Nb, Ta, Zr, Hf, P, Ti etc. The trace element indicate that the Phl-Amp harzburgites have island arc signature. Their ~(87)Sr/~(86)Sr are varied from 0.708912 to 0.879839, ~(143)Nd/~(144)Nd from 0.511993 to 0.512164, ε Nd from- 9.2 to - 12.6. Rb/Sr isochrone age of the phlogolite amphibole harzburgite shows the metasomatism took place at 41Ma, and the Amp ~(40)Ar/~(39)Ar cooling age indcate the Phl-Amp harzburgite raising at 16Ma. There is an intense crust shortening resulted from the thrust faults and folds in the Cayu block which is shortened more 120km than that of the Lasha block in 35～90Ma. With the NE corner of the India plate squash into the Gangdese arc, the sinistral Pai shear fault and the dextral Aniqiao shear fault on the both sides of the Great bent of Yalun Zangbu river come into active in 21～26Ma. On the other hand, the right-lateral Gongrigabu strike-slip faults come into activity at the same period, a lower age bound for the Gongrigabu strike-slip fault is estimated to be 23～24Ma from zircon of ion-probe U/Pb thermochronology. The Gongrigabu strike-slip faults connect with the Lhari strike-slip fault in the northwestern direction and with the Saganing strike-slip at the southeastern direction. Another important structure in the EHS is the Gangdese detachment fault system (GDS) which occurs between the sedimental cover and the metamorphic basement. The lower age of the GDS is to be 16Ma from the preliminary 40Ar/39Ar thermochronology of white mica. The GDS is thought to be related to the reverse of the subducted Indian crust and the fast uplift of the EHS. Structural and thermochronology investigation of the EHS suggest that the eastern Tibet and the western Yunnan rotated clockwise around the EHS in the period of 35～60Ma. Later, the large-scale strike-slip faults (RRD, Gaoligong and Saganing fault) prolongate into the EHS, and connect with the Guyu fault and Gongrigabu fault, which suggest that the Indianchia block escape along these faults. Two kind of magmatic rocks in the EHS have been investigated, one is the mantle-derived amphibole gabbro, dioposide diorite and amphibole diorite, another is crust origin biotit-garnet adamellite, biotit-garnet granodiorite and garnet-amphibole-biotite granite. The amphibole gabbro dioposite diorite and amphibole diorite are rich in LREE, and LILE, such as Ba, Rb, Th, K, Sr etc, depleted in HFSE, such as Nb, Ta, Zr, Hf, Ti etc. The ratio of ~(87)Sr/~(86)Sr are from 0.7044 to 0.7048, ~(143)Nd/~(144)Nd are from 0.5126 to 0.5127. The age of the mantle origin magamatic rocks, which result from the partial melt of the raising and decompression anthenosphere, is 8Ma by ~(40)Ar/~(39)Ar dating of amphibole from the diorite. The later crust origin biotite-garnet adamellite, biotite-garnet granodiorite and garnet-amphibole-biotite granite are characterized by aboudance in LREE, and strong depletion of Eu. The ratios of ~(87)Sr-~(86)Sr are from 0.795035 to 0.812028, ~(143)Nd/~(144)Nd from 0.51187 to 0.511901. The ~(40)Ar/~(39)Ar plateau age of the amphibole from the garnet-amphibole-biotite granite is 17.5±0.3Ma, and the isochrone age is 16.8±0.6Ma. Their geochemical characteristics show that the crust-derived magmatic rocks formed from partial melting of the lower curst in the post-collisional environment. A group of high-pressure kaynite-garnet granulites and enclave of high-pressure garnet-clinopyroxene grnulites and calc-silicate grnulites are outcroped along the MMT. The peak metamorphic condition of the high-pressure granulites yields T=800～960 ℃, P=1.4～1.8Gpa, corresponding the condition of 60km depth. The retrograde assemblages of the high-pressure grnulites occur at the condition of T=772.3～803.3 ℃, P=0.63～0.64Gpa. The age of the peak metamorphic assemblages are 45 ～ 69Ma indicated by the zircon U/Pb ion-plobe thermochronology, and the retrograde assemblage ages are 13～26Ma by U/Pb, ~(40)Ar/~(39)Ar thermochronology. The ITD paths of the high-pressure granulites show that they were generated during the tectonic thickening and more rapid tectonic exhumation caused by the subducting of the Indian plate and subsequent break-off of the subducted slab. A great deal of apatite, zircon and sphene fission-track ages, isotopic thermochronology of the rocks in the EHS show that its rapid raising processes of the EHS can be divided into three main periods. There are 35～60Ma, 13～25Ma, 0～3Ma. 3Ma is a turn in the course of raising in the EHS which is characterized by abruptly acceleration of uplifting. The uplift ratios are lower than 1mm .a~(-1) before 3Ma, and higher than 1mm .a~(-1) with a maximum ratio of 30mm .a~(-1) since 3Ma. The bottom (knick point) of the partial anneal belt is 3.8km above sea level in the EHS, and correspond to age of 3Ma determined by fission-track age of apatite. The average uplift ratio is about 1.4 mm .a~(-1) below the knick point. The EHS has raised 4.3km from the surface of 2.36km above sea level since 3Ma estimated by the fossil partial anneal belt of the EHS. We propose a two-stage subduction model (B+A model) basing on Structural, thermochronological, magmatical, metamorphic and geophysical investigations of the EHS. The first stage is the subduction of the Indian continental margin following after the subduction of the Tethys Ocean crust and subsequent collision with the Gangdese arc, and the second stage is the Indian crust injecting into the lower crust and upper mantle of the Tibet plateau. Slab break-off seems to be occurred between these two stages.

藏东南迦巴瓦变质岩楔入体东边界阿尼桥断裂带构造变形性质、年代学与构造意义

The Namche Barwa metamorphic rock indenter is a part of the Indian plate. The Aniqiao fault, a northeastern striking shear zone, is the eastern boundary of the Namche Barwa metamorphic rock indenter. The activities of the Aniqiao fualt reflects the history of structure deformation and uplift of the Namche Barwa metamorphic rock indenter. In this dissertation, studied the history of activities of the Aniqiao fault, I study the deformation of the Namche Barwa metamorphic rock indenter based on which, I try to discuss the history of action and deformation of the eastern Tibet. The Aniqiao fault composes of mica quartz schist. With observing in the field and by the microscope, there are at least two stages of deformation. The earlier is right lateral striking, the later is normal striking. The biotite, in the hornblende biotitic mylonite in western footwall, the muscovite and sericite, in the mica quartz schist in eastern hangingwall, show 4 plateau and isochron ages: 3.7-3.3Ma, 6.8-6.4Ma, 13.4-13.2Ma, 23.9Ma, by ~(40)Ar/~(39)Ar. Combine the characteristics of kinematics with the characteristics of isotopic ages, this dissertation figured three stages of deformation: in 23.9Ma and 13.4-13.2 Ma, the Aniqiao fault undertook twice strike-slip deformation; in 6.8Ma-6.4Ma, the Aniqiao fault occurred normal strike deformation; in 3.7-3.3Ma, there was another thermal case which maybe relating to uplift. Combine the deformation of the Aniqiao fault and the deformation of the western boundary fault of the Namche Barwa metamorphic rock indenter, this dissertation considers that the Namche Barwa metamorphic rock indenter has occurred three defomational cases during the period of Oligocene and Quaternary: in 23Ma and 13Ma, the Namche Barwa metamorphic rock indenter wedged into the Gangdisi granite zone; from 6-7Ma, the Namche Barwa metamorphic rock indenter begins to uplift. From 6-7Ma, the Namche Barwa metamorphic rock indenter must has been occurred multi-stage uplifting. The indentation of the Namche Barwa metamorphic rock indenter is correspond to the structure escape of the Chuanxi, Dianxi blocks. In the surface deformation, the movement of these blocks are very harmonious.

Uniformity of karyotypes in Ligularia (Asteraceae : Senecioneae), a highly diversified genus of the eastern Qinghai-Tibet Plateau highlands and adjacent areas

Ligularia, a highly diversified genus in the eastern Qinghai-Tibet Plateau and adjacent areas, was chosen as a suitable subject in which to study speciation patterns in this 'hot spot' area at the chromosomal level. Chromosome numbers and karyotypes were studied in 23 populations of 14 species, most of which are endemic to this area. The basic number x = 29 was confirmed for all species. Ligularia virgaurea was found to have diploid and triploid cytotypes, 2n = 58 and 87. Other species are only diploid, with 2n = 58. The karyotypes of all populations within any species, and all species spanning most sections and covering most of the morphological range in Ligularia, are very similar to each other, belonging to type 2A according to Stebbin's classification. This karyotype was also found in its close allies, e.g. Cremanthodium, Ligulariopsis, Parasenecio, and Sinacalia. Aneuploid reduction of chromosome number from 2n = 60 to 58 and karyotypic variation was found in Ligularia and its allies. Such a chromosomal pattern with few polyploids infers that variation of karyotype structure at the diploid level seems to be the predominant feature of chromosomal evolution in this group and sympatric speciation via hybridization and polyploidization has played a minor role in its species diversity. (C) 2004 The Linnean Society of London

Potential refugium on the Qinghai-Tibet Plateau revealed by the chloroplast DNA phylogeography of the alpine species Metagentiana striata (Gentianaceae)

Metagentiana striata is an alpine annual herbaceous plant endemic to the east of the Qinghai-Tibet (Q-T) Plateau and adjacent areas. The phylogeography of M. striata was studied by sequencing the chloroplast DNA (cpDNA) trnS-trnG intergenic spacer. Ten haplotypes were identified from an investigation of 232 individuals of M. striata from 14 populations covering the entire geographical range of this species. The level of differentiation amongst populations was very high (G(ST) = 0.746; N-ST = 0.774) and a significant phylogeographical structure was observed (P < 0.05). An analysis of molecular variance found a high variation amongst populations (76%), with F-ST = 0.762 (highly significant, P < 0.001), indicating that little gene flow occurred amongst the different regions; this was explained by the isolation of populations by high mountains along the Q-T Plateau and adjacent areas (N-m = 0.156). Only one ancestral haplotype (A) was common and widespread throughout the distributional range of M. striata. The populations of the Hengduan Mountains region of the south-eastern Q-T Plateau showed high diversity and uniqueness of haplotypes. It is suggested that this region was the potential refugium of M. striata during the Quaternary glaciation, and that interglacial and postglacial range expansion occurred from this refugium. This scenario was in good agreement with the results of nested clade analysis, which inferred that the current spatial distribution of cpDNA haplotypes and populations resulted from range expansion, together with past allopatric fragmentation events. (c) 2008 The Linnean Society of London.