横断山南段上新世的植被多样性与分布格局

横断山南段复杂的地形地貌和多样的气候环境造就了高度丰富的植被多样性。这种植被多样性的演化与形成是植物学、生态学等领域共同关注的科学问题, 而植物化石是回答这一科学问题的重要媒介。本文基于横断山南段的9个上新世化石植物群, 根据其植物组成和优势成分, 分析其所代表的植被类型, 总结了该地区上新世的植被多样性与空间分布, 并结合古环境研究资料, 探讨该地区植被多样性的兴起, 植被分布格局的形成, 及其与环境变迁之间的关联。结果显示, 横断山南段在上新世时期已经具有了多种植被类型, 包括亚热带常绿阔叶林、亚热带落叶阔叶林、硬叶常绿阔叶林、针阔叶混交林、灌丛草地等, 体现了丰富的植被多样性; 植被类型从南面的偏热性植被向北面的偏温性植被逐渐转变, 反映了当时随纬度变化的海拔梯度, 植被类型与分布呈现出与现在高度相似的格局。同时, 小范围内也具有适应于不同气候的植被类型, 反映了当地较大的海拔落差, 可能与高大山体的存在有着密切关联。我们推测, 横断山南段现在丰富的植被多样性和随纬度变化的植被面貌最晚在上新世就已基本形成, 但形成时间是否更早则需要更多、更老化石植物群的发现与研究。     

横断山北部高山区不同生态条件下土壤微生物数量及其与生态因子的相关性

采用全球定位系统(GPS)采集了横断山北部高山区35个样点的土样,用稀释平板法对该区细菌、真菌和放线菌进行分离计数,并分析了微生物数量与土壤养分、土壤水分、土地利用方式和pH等因子的相关性。结果表明,该区域3大类土壤微生物数量表现为细菌>放线菌>真菌。土壤微生物数量在不同区域表现为松林口>雀儿山>折多山;林地微生物比草地丰富,但不及草地微生物均衡。微生物数量与土壤理化因子间的相关分析表明,放线菌数量与pH呈显著正相关,真菌数量与土壤全钾含量呈极显著正相关。     

Pollen Morphology of Plants from the Hengduan Mountains and Their Ecological Significance

Pollen morphology of selected taxa from the Hengduan Mountains, Southwest China are investigated in the present study. Forty eight taxa (flowering in the summer, 46 species and 2 varieties) of 43 genera belonging to 27 families were observed by light and scanning electron microscopy. Pollen morphology is described in detail. Two pollen shapes are mainly found in these species: subprolate to prolate (271%) and prolate (25%). Spheroidal, subspheroidal to subprolate, suboblate and tetrad shapes can also be found in some species. Aperture type is mostly tricolporate, with a percentage of 438, and also contains tricolpate, pantoporate, stephanocolpate, 3 colporoid, 6 colpate, monocolpate. The most common ornamentation is finely reticulate, with a percentage of 50. Other exine ornamentations, such as coarsely reticulate, finely granulate, smooth, spinulose are also observed. The palynological documentation of these species will provide the modern palynological basis for paleopalynological studies of the Quaternary Strata. On the basis of pollen morphology characters, identification features of some species in the same families were discussed according to the results of cluster analysis used by SPSS. The ecological significance was also discussed based on the ecological properties of these taxa.     

云南横断山区小型兽类物种多样性与地理分布趋势

以云南横断山区的高黎贡山、怒山和云岭等重要山脉的7个山系作为样区,进行小型兽类的垂直分布调查并参考有关资料,采用不同山系样区各垂直带小型兽类物种多样性指数的平均值作为指标,对横断山区小型兽类的地理分布趋势、规律和相关影响因素进行了研究。结果表明：小型兽类物种多样性的地理分布趋势是由南向北,由西向东呈递减的趋势。与此趋势变化密切相关的主要因素是纬度的影响,其次是水湿条件,另外还与小型兽类的密度,物种丰富度、地理环境（坡向）和垂直带的影响等因素有关。此外,对横断山区不同区域小兽物种密度高峰问题作了分析和讨论。     

云南横断山区蚤类物种多样性的地理分布趋势与重要环境因素的关系

根据云南横断山区具代表性的7个山系共9个样区山地蚤类及其宿主动物的垂直分布调查结果,并参考以往的部分调查资料,对所获数据进行统计学处理,应用不同山系样区各垂直带蚤类物种多样性的平均值作为指标,就云南横断山区蚤类物种多样性的地理分布趋势和规律,与宿主动物和重要环境因素的关系等问题进行了分析和探讨。结果显示,蚤类物种多样性的地理分布趋势是由西北→南→东→北呈递减的趋势。与变化趋势密切相关的重要因素是水湿条件,其次是经度的影响。另外还与蚤类的丰富度、地理环境、垂直带和人们的生产活动等因素有关。研究认为,形成蚤类与宿主动物间多样性地理分布趋势上的差异的主要原因是对环境的适应性不同,其中水湿条件就是很重要的因素之一。研究还发现,横断山蚤类在我国蚤类区系中是多样性最高的地区,它充分地反映了横断山区栖息地异质性对物种数的重要影响,并说明栖息地异质性对物种—面积关系起着重要作用。     

Rivers as barriers for high elevation amphibians: a phylogeographic analysis of the alpine stream frog of the Hengduan Mountains

At high altitude, rivers may function as barriers for amphibians. We examined 21 populations of Scutiger boulengeri from the Hengduan Mountains with 1038 base pairs of mitochondrial cytochrome b gene sequences. The haplotypes of S. boulengeri formed three clades on the gene tree, and each clade was restricted to one mountain ridge separated by two major river systems, the Yalong River and the Dadu River. The vicariant pattern of the gene tree suggests that these rivers functioned as effective barriers during population differentiation. On the other hand, mountain ridges may have facilitated amphibian movement. Populations within the uninterrupted mountain ranges of clades II and III, revealed little genetic structure. The northern clade I, harboured a substantial amount of genetic variation, which might be the consequence of the rugged terrain and heterogeneous habitat of this area. Furthermore, one outgroup species, Scutiger glandulatus , formed the fourth clade and nested within S. boulengeri , suggesting that S. boulengeri is likely a paraphyletic species or a species complex.     

云南横断山区蚤类物种丰富度与区系的垂直分布格局

为探讨横断山区蚤类物种丰富度与区系垂直分布格局的基本规律以及影响它们分布的主要生态因子,本文以云南西部横断山区18个山峰为主体,对海拔高度在1000–5000m之间已知分布的9科43属142种(亚种)蚤类的垂直分布资料进行综合整理和统计分析。结果显示:(1)蚤类的属丰富度、物种丰富度、特有种丰富度和特有度以及不同区系成分物种丰富度的垂直分布都呈现随海拔先增高后降低的单峰分布格局,最大峰值出现在中山海拔2500–3800m之间;(2)东洋和古北两区系成分物种构成比的垂直分布格局截然不同,前者随着海拔梯度的升高基本递减,后者则随着海拔的升高递增,垂直分布格局反映了它们沿纬度梯度分布的一般规律;(3)聚类分析将横断山9个不同海拔带的蚤类归为6个生态类型,反映出海拔高度、气候环境和森林植被等重要因素对蚤类分布的影响以及蚤类群落的组成、分布沿海拔梯度变化的一般规律,表达了蚤类分布与环境条件的统一性;(4)β多样性沿海拔梯度呈现为双峰形分布格局,两高峰值都反映出蚤类的组成和分布在不同气候环境和植被带之间的过渡与转变,说明β多样性垂直分布格局与海拔梯度上的气候和生境的变化程度有关。研究认为,中山地段物种丰富度高峰的形成主要是由于两大动、植物区系过渡区的边缘效应和山地水湿条件的影响。影响该区域蚤类垂直分布格局的综合因素有山体海拔高度、动植物区系过渡区的边缘效应、山地雨量分配特征、气候环境条件以及人们的生产活动等。     

青藏高原生态屏障生态系统时空演变及驱动机制

青藏高原生态屏障是我国生态安全战略格局的重要组成部分,对我国乃至亚洲生态安全具有重要的屏障作用。研究青藏高原生态屏障生态格局的演变规律,探究影响生态系统变化的驱动机制,对青藏高原生态屏障建设和保障国家生态安全具有重要的意义。利用多源遥感数据,分析了2000-2015年国家屏障区生态格局演变规律,选取了自然和社会经济等驱动要素,采用冗余分析等方法解析了青藏高原生态屏障生态系统演变机制。结果表明：（1）2000-2015年间,青藏高原生态屏障生态系统格局发生明显变化,草地生态系统减少了1792 km²,主要转化为荒漠生态系统和河流生态系统,转换面积分别为1088 km²和832 km²;河流生态系统增加了1600 km²,主要由荒漠生态系统和草地生态系统转换而来,分别转换了1152 km²和832 km²。（2）2000-2015年青藏高原生态屏障生态系统格局演变驱动机制中以社会经济因子为主。冗余分析结果显示国内生产总值（83%）和人口数量（72%）贡献率最大;方差分析结果中国内生产总值和人口数量的共同贡献率达到了77%;地理加权回归结果显示生态系统演变受社会经济因子主导的区域面积比例为60.41%。（3）青藏高原生态屏障内人口数量的总贡献率达到了72%,在人口数量作用下生态系统呈正向转换的面积占比达到了86.24%,且人口数量与河流、森林生态系统的相关程度较高,综合说明了青藏高原生态屏障内生态保护政策的实施、生态工程的建设卓有成效。     

Chromosome counts and karyotypes in Chaetoseris and Stenoseris (Asteraceae-Cichorieae) from the Hengduan Mountains of SW China

Chaetoseris and Stenoseris are two morphologically close genera from the tribe Cichorieae of the sunflower family and they are endemic in alpine eastern Himalayas to the Hengduan Mountains of SW China.Mitotic chromosome numbers and karyotypes are reported for 12 populations representing eight species of Chaetoseris and two species of Stenoseris from the Hengduan Mountains region.Eight species are new and the other two provide confirmation of previous reference.All Chaetoseris and Stenoseris taxa are diploidy with 2n ＝ 16 and their basic number is tentatively suggested as x ＝ 8.Karyotypes of Chaetoseris and Stenoseris are similar to each other with 2A and 2B for the former and 2A for the latter.Cytological data of chromosomal numbers and karyotypes support a close relationship of the two genera.Currently no polyploids are found for these two genera and it seems that polyploidization has played a minor role in their evolutionary speciation in the Hengduan Mountains region.     

Plant diversity and floristic characters of the alpine subnival belt flora in the Hengduan Mountains,SW China

There have been few studies of the alpine subnival belt flora in the Hengduan Mountains (HM), which host remarkable biodiversity. To extend knowledge of this flora, we examined published florae, herbarium specimens, and field observations (and material) collected by both ourselves and others. In total, 942 seed plant species have been recorded in the belt, representing 168 genera and 48 families. Twenty-four large families (with ≥10 species) are present, represented by 873 species (92.68% of the total). These include Asteraceae, Saxifragaceae, and Brassicaceae (146, 82, and 71 species, respectively). There are also 27 large genera (represented by ≥10 species), collectively contributing 587 species (62.31%) to the flora, including Saxifraga, Corydalis, and Saussurea (75, 55, and 49 species, respectively). Areal elements represented by the highest numbers of genera are the North temperate, Sino-Himalaya, and Old World temperate elements (39.88%, 14.29%, and 12.50%, respectively), while the Hengduan Mountains, Sino-Himalaya, and Qinghai-Tibetan Plateau elements are most species-rich (355, 281, and 161 species, respectively), collectively accounting for 84.61% species of the known flora. Of these, 295 species (31.32%) are endemic to the Sino-Himalayan alpine subnival belt and 151 (16.03%) strictly endemic to the alpine subnival belt of the HM. These findings indicate that the flora is young, strongly differentiated, probably developed as a result of the plateau's uplift, and speciation has been accelerated by the harsh environment and strong heterogeneity of niches.     

Different trends and divergent responses to climate factors in the radial growth of Abies georgei along elevations in the central Hengduan Mountains

Climate change has been unprecedented in the last half-century. Tree growth dynamics and responses to climate warming at different elevations vary by study area due to regional diversity in site-specific climatic conditions in the central Hengduan Mountains. A. georgei is the dominant species in high-elevation montane forests in the central Hengduan Mountains. To study the response of A. georgei radial growth to climate and identify tree growth trends at different elevations, tree-ring width chronologies at four elevations across the subalpine A. georgei forest belt were built and growth-climate relationships were analyzed. The primary findings of this study were as follows: (1) radial growth rates of A. georgei decreased with elevation; (2) warming alleviated the limitation of low temperatures and abundant precipitation on tree radial growth at the highest sampling site; and (3) unlike at other elevations, the trend of trees basal area increment (BAI) at the lowest sampling site showed a significant decline over the past 20 years. This suggests the presence of an elevational inflection point, likely between 3800 m and 4000 m, where tree growth trends diverge. These results confirmed that A. georgei at higher elevation in the central Hengduan Mountains currently benefits from higher temperatures. However, the effects of drought on A. georgei at lower elevations would cause radial growth to decrease with climate warming. Therefore, it is critical to establish effective management strategies based on how A. georgei responds to climate change at various elevations.     

DNA barcoding of Rhododendron (Ericaceae), the largest Chinese plant genus in biodiversity hotspots of the Himalaya–Hengduan Mountains

The Himalaya–Hengduan Mountains encompass two global biodiversity hotspots with high levels of biodiversity and endemism. This area is one of the diversification centres of the genus Rhododendron, which is recognized as one of the most taxonomically challenging plant taxa due to recent adaptive radiations and rampant hybridization. In this study, four DNA barcodes were evaluated on 531 samples representing 173 species of seven sections of four subgenera in Rhododendron, with a high sampling density from the Himalaya–Hengduan Mountains employing three analytical methods. The varied approaches (nj , pwg and blast ) had different species identification powers with blast performing best. With the pwg analysis, the discrimination rates for single barcodes varied from 12.21% to 25.19% with ITS < rbcL < matK < psbA‐trnH. Combinations of ITS + psbA‐trnH + matK and the four barcodes showed the highest discrimination ability (both 41.98%) among all possible combinations. As a single barcode, psbA‐trnH performed best with a relatively high performance (25.19%). Overall, the three‐marker combination of ITS + psbA‐trnH + matK was found to be the best DNA barcode for identifying Rhododendron species. The relatively low discriminative efficiency of DNA barcoding in this genus (~42%) may possibly be attributable to too low sequence divergences as a result of a long generation time of Rhododendron and complex speciation patterns involving recent radiations and hybridizations. Taking the morphology, distribution range and habitat of the species into account, DNA barcoding provided additional information for species identification and delivered a preliminary assessment of biodiversity for the large genus Rhododendron in the biodiversity hotspots of the Himalaya–Hengduan Mountains.     

五种齿突蟾在横断山南潜在地理分布预测

由于栖息地质量下降,近年来齿突蟾属物种种群数量急剧减少,明确齿突蟾属物种空间分布,是监测、管理、保护齿突蟾属物种的基础。横断山区可能是齿突蟾属的起源中心和分化中心,但齿突蟾属在横断山区的地理分布格局尚不明确。利用优化后Maxent模型,首次预测西藏齿突蟾Scutiger boulengeri、刺胸齿突蟾Scutiger mammatus、胸腺齿突蟾Scutiger glandulatus、圆疣齿突蟾Scutiger tuberculatus、贡山齿突蟾Scutiger gongshanensis 5种高海拔齿突蟾属物种在横断山南生物多样性保护优先区域的潜在地理分布,并分析其与环境因子的关系。结果显示,5种齿突蟾属物种在横断山南的潜在地理分布格局存在差异,西藏齿突蟾主要分布在横断山南的北部,圆疣齿突蟾主要分布在横断山南东北部的四川省境内,贡山齿突蟾主要分布在横断山南的西南部,刺胸齿突蟾和胸腺齿突蟾的潜在分布格局较为相似,在横断山南的中部、西北部地区都有较多分布,但胸腺齿突蟾潜在分布区更为碎片化。另外,横断山南北部地区的齿突蟾属丰富度明显高于南部地区。环境变量贡献率和刀切法结果显示温度因子和降水因子是决定横断山南齿突蟾属潜在分布的主要因素,最冷季降水量对西藏齿突蟾、贡山齿突蟾、圆疣齿突蟾潜在分布有重要影响,但它们对最冷季降水量的偏好存在差异。此外,研究也显示,通过评估潜在的Maxent参数组合,选择最佳的Maxent模型是有效且必要的。     

Chromosome counts and karyotypes in Chaetoseris and Stenoseris (Asteraceae‐Cichorieae) from the Hengduan Mountains of SW China

Abstract Chaetoseris and Stenoseris are two morphologically close genera from the tribe Cichorieae of the sunflower family and they are endemic in alpine eastern Himalayas to the Hengduan Mountains of SW China. Mitotic chromosome numbers and karyotypes are reported for 12 populations representing eight species of Chaetoseris and two species of Stenoseris from the Hengduan Mountains region. Eight species are new and the other two provide confirmation of previous reference. All Chaetoseris and Stenoseris taxa are diploidy with 2n= 16 and their basic number is tentatively suggested as x= 8. Karyotypes of Chaetoseris and Stenoseris are similar to each other with 2A and 2B for the former and 2A for the latter. Cytological data of chromosomal numbers and karyotypes support a close relationship of the two genera. Currently no polyploids are found for these two genera and it seems that polyploidization has played a minor role in their evolutionary speciation in the Hengduan Mountains region.     

Elevational gradients of diversity for lizards and snakes in the Hengduan Mountains,China

Comparing elevational gradients across a wide spectrum of climatic zones offers an ideal system for testing hypotheses explaining the altitudinal gradients of biodiversity. We document elevational patterns of lizard and snake species richness, and explore how land area and climatic factors may affect species distributions of lizards and snakes. Our synthesis found 42 lizard species and 94 snake species known from the Hengduan Mountains. The lizards are distributed between 500 and 3500 m, and the snakes are distributed between 500 and 4320 m. The relationship between species richness and elevation for lizards and snakes is unimodal. Land area explains a significant amount of the variation in lizard and snake species richness. The cluster analysis reveals pronounced distinct assemblages for lizards and snakes to better reflect the vertical profiles of climate in the mountains. Climatic variables are strongly associated with lizard and snake richness along the elevational gradient. The data strongly implicate water availability as a key constraint on lizard species richness, and annual potential evapotranspiration is the best predictor of snake species richness along the elevational gradient in the Hengduan Mountains.     

基于染色体计数和ITS序列初步探讨横断山区柴胡属植物(伞形科)的系统发育

横断山区是中国柴胡属Bupleurum植物的分布中心。本文对横断山区6个种2变种进行了染色体记数报道,其中4个种2变种是首次报道。对横断山区的10个种4个变种、中国北方（河北和黑龙江）的3个种的nrDNA ITS进行测序,同时从GenBank里面下载同属的来自非洲和地中海西部的16个nrDNA ITS序列数据,结合染色体数目变化结果,初步探讨了横断山区柴胡属植物的系统发育。结果表明横断山区可能是现代柴胡属植物的频度中心和多样分布中心之一。它们的祖先种可能是非洲北部的木本柴胡属植物B.fruticosum,或者是地中海西部的柴胡属植物,推测是通过中东和高加索扩散而形成的,其中与非洲南部特有种B.mundtii的亲缘关系也较近;染色体基数演化趋势是：8是较原始基数,6和7是次生基数,其染色体异基数变异和多倍化可能是物种形成、进化以及向外扩散的主要方式;在ITS系统发育树中,中国柴胡属植物染色体基数为8的种类聚为一支,染色体基数为6和7的种类聚为了一支,不支持舒璞等（1998）关于中国柴胡属的属下分类系统。结合已有的形态学、细胞学、孢粉学证据和ITS系统发育树,建议窄竹叶柴胡B.marginatum var.stenophyllum独立成种。     

Phylogenetic inference of the genus Bupleurum (Apiaceae) in Hengduan Mountains based on chromosome counts and nuclear ribosomal DNA ITS sequences

pleurum of Apiaceae in China. This paper reports chromosome numbers of six species and two varieties of Bupleurum, and for four species and two varieties their chromosome numbers are reported for the first time. The phylogeny of Bupleurum was investigated based on the ITS region of the nuclear ribosomal DNA (nrDNA) of 14 taxa from the Hengduan Mountains, 3 taxa from the North China (Hebei and Heilongjiang), and 16 taxa from Africa and the Mediterranean region. Varia-tions in chromosome numbers and the ITS sequences were used to infer phylogenetic relationships between Bupleurum species in Hengduan Mountains. The results showed that the Hengduan Mountains might represent one of the frequency and diversity centers for Bupleurum. The ancestors of Bupleurum species in the Hengduan Mountains may be related to the woody B. fruticosum in North Africa, or the species in the western Mediterranean region. It is postulated that the ancestral population migrated into Hengduan Mountains through the Middle East and the Caucasus. Furthermore, the neo-endemic B. mundtii in South Africa appeared to be a close relative of the species in the Hengduan Mountains. In the trend of basic chromosome number evolution, x = 8 should be regarded as the ancestral basic number, while x = 6, 7 as the derived ones. The Bupleurum species in the Hengduan Moun-tains have been undergoing changes in the basic chromosome numbers or the ploidy level. The ITS phylogenetic tree showed that the Chinese species were divided into two clades: one with the basic chromosome number x = 8, and the other with x = 6, 7. The results rejected the previous infrageneric classification of Bupleurum in China. We further suggested to raise B. marginatum var. stenophyllum to species rank based on the combined evidence from morphology, karyology, pollen morphology, and the ITS phylogenetic tree.