中国卧龙自然保护区不同海拔川滇高山栎(Quercus aquifolioides)群体的遗传变异

海拔梯度造成的环境异质性，如崎岖的地形、复杂的植被结构以及花期延迟等可能会极大地影响到物种的形态和遗传变异格局。理解物种形态和遗传变异的海拔格局对于物种多样性的管理和保护是非常重要的。尽管植物群体遗传学是一个飞速发展的研究领域，然而与海拔相关的形态变异、遗传变异及群体间遗传差异的研究却很少。到目前为止，还不清楚遗传变异与海拔之间是否必然的相关性。 川滇高山栎是一种重要的生态和经济型树种，广泛分布于中国西南的四川、西藏、贵州和云南省的高海拔地区，在保持水土、调节气候方面起着十分重要的作用。尽管主要受阳光限制而仅分布于阳坡，但其海拔梯度范围较大，表明川滇高山栎对不同的环境具有很强的适应性。本文通过叶型及生理响应、微卫星分子标记和扩增性片段长度多态性方法，试图探索川滇高山栎叶沿海拔梯度的形态和生理响应及其沿海拔梯度的遗传变异格局，为川滇高山栎的保护和利用提供进一步的遗传学理论依据和技术指导。 对叶形、含氮量及碳同位素的试验结果表明，平均比叶面积、气孔密度、气孔长度和气孔指数等气孔参数随海拔的升高呈非线性变化。在海拔大于2800 m时，川滇高山栎的比叶面积、气孔长度和气孔指数都随海拔升高而降低，但是在海拔小于2800 m时，这些指标都随海拔的升高而增大。相对而言，单位叶面积的含氮量和碳同位素则表现出相反的变化模式。另外，比叶面积是决定碳同位素沿海拔梯度变化的最重要参数。本研究结果表明，海拔2800 m附近是川滇高山栎生长和发育的最适地带，在这里生长的植物叶片厚度更薄、气孔更大、叶碳同位素值更小。 利用六对微卫星引物对五个不同海拔川滇高山栎群体遗传多样性进行研究，结果表明，群体内表现出较高的遗传多样性，平均每位点等位基因数11.33个，平均期望杂合度达0.820。群体间差异较小，分化仅为6.6％。聚类分析也并没有显示出明显的海拔格局。然而低频率等位基因却与海拔呈显著性正相关(R2=0.97, P < 0.01)，表明在高海拔处，川滇高山栎以更多的稀有基因来适应恶劣的环境条件。本试验结果表明由海拔梯度形成的选择性压力对川滇高山栎群体的遗传变异影响并不明显。 为了进一步探讨川滇高山栎群体遗传变异与海拔之间的相互关系，我们还对其进行了扩增性片段长度多态性分析。结果表明：(1)随海拔的升高(从群体WL2到群体WL5)，群体内遗传变异降低，而群体间遗传差异增加；(2)低海拔群体WL1表现出最低的遗传变异性(HE = 0.181)，同时与其余四个群体间呈现出最大的遗传差异性(平均FST = 0.0596)；(3)在除去低海拔群体WL1后，Mantel检测表明群体间遗传距离与海拔距离之间表现出正相关性。另外，研究结果还表明，遗传变异受生境条件(过度的湿热环境)及人为干扰(火烧、砍伐和放牧)的影响，这一点至少在低海拔群体WL1上发生了作用。 通过叶形态、生理及DNA分子水平的研究，结果表明叶形态特征和碳同位素与海拔紧密相关，与海拔之间呈非线性变化，海拔2,800 m附近是川滇高山栎生长和发育的最适地带。海拔梯度在一定程度上会影响到川滇高山栎群体的遗传变异结构，但在这样一个狭窄的地理分布区域里，这种影响并不足以导致群体间较大的遗传分化。同时生境条件及人为干扰也是影响遗传变异的限制性因子，不容忽视。 Altitudinal gradients impose heterogeneous environmental conditions, such as rugged topography, a complex pattern of vegetation and flowering delay, and they likely furthermore markedly affect the morphological and genetic variation pattern of a species. Understanding altitudinal pattern of morphological and genetic variation at a species is important for the management and conservation of species diversity. Although plant population genetics is a fast growing field of research, there are only few recent investigations, which analyzed the genetic differentiation and changes of intra-population variation along altitudinal gradients. At present, it is still unclear whether there are some common patterns of morphological and genetic variation with altitude. Quercus aquifolioides Rehder & E.H. Wilson, which is an important ecological and economical endemic woody plant species, is widely distributed in the Yunnan and Sichuan provinces, Southwest China. Its large range of habitat across different altitudes implies strong adaptation to different environments, although it is mainly restricted to sunny, south facing slopes. It plays a very important role in preventing soil erosion, soil water loss and regulating climate, as well as in retaining ecological stability. In this paper, we tried to understand the altitudinal pattern of morphological and genetic variation along altitudinal gradients through the experiments of leaf morphological and physiological responses, microsatellite analysis and AFLP markers. In leaf morphological and physiological responses experiment, we measured leaf morphology, nitrogen content and carbon isotope composition (as an indicator of water use efficiency) of Q. aquifolioides along an altitudinal gradient. We found that these leaf morphological and physiological responses to altitudinal gradients were non-linear with increasing altitude. Specific leaf area, stomatal length and index increased with increasing altitude below 2,800 m, but decreased with increasing altitude above 2,800 m. In contrast, leaf nitrogen content per unit area and carbon isotope composition showed opposite change patterns. Specific leaf area seemed to be the most important parameter that determined the carbon isotope composition along the altitudinal gradient. Our results suggest that near 2,800 m in altitude could be the optimum zone for growth and development of Q. aquifolioides, and highlight the importance of the influence of altitude in research on plant physiological ecology. Genetic variation and differentiation were investigated among five natural populations of Q. aquifolioides occurring along an altitudinal gradient that varied from 2,000 to 3,600 m above sea level in the Wolong Natural Reserve of China, by analyzing variation at six microsatellite loci. The results showed that the populations were characterized by relatively high intra-population variation with the average number of alleles equaling 11.33 per locus and the average expected heterozygosity (HE) being 0.779. The amount of genetic variation varied only little among populations, which suggests that the influence of altitude factors on microsatellite variation is limited. However, there is a significantly positive correlation between altitude and the number of low-frequency alleles (R2=0.97, P < 0.01), which indicates that Q. aquifolioides from high altitudes has more unique variation, possibly enabling adaptation to severe conditions. F statistics showed the presence of a slight deficiency of heterozygosity (FIS=0.136) and a low level of differentiation among populations (FST=0.066). The result of the cluster analysis demonstrates that the grouping of populations does not correspond to the altitude of the populations. Based on the available data, it is likely that the selective forces related to altitude are not strong enough to significantly differentiate the populations of Q. aquifolioides in terms of microsatellite variation. To further elucidate genetic variation pattern of Q. aquifolioides populations under sub-alpine environments, genetic variation and differentiation were investigated along altitudinal gradients using AFLP markers. The altitudinal populations with an average altitude interval of 400 m, i.e. WL1, WL2, WL3, WL4 and WL5, correspond to the altitudes 2,000, 2,400, 2,800, 3,200 and 3,600 m, respectively. Our results were as follows: (i) decreasing genetic variation (ranging from 0.253 to 0.210) and increasing genetic differentiation with altitude were obtained from the WL2 to the WL5 population; (ii) the WL1 population showed the lowest genetic variation (HE = 0.181) and the highest genetic differentiation (average FST = 0.0596) with the other four populations; (iii) the positive correlation was obtained using Mantel tests between genetic and altitude distances except for the WL1 population. Our results suggest that altitudinal gradients may have influenced the genetic variation pattern of Q. aquifolioides populations to some extent. In addition, habitat environments (unfavorable wet and hot conditions) and human disturbances (burning, grazing and felling) were possible influencing factors, especially to the low-altitude WL1 population. The present study shows that there were close correlations between morphological features and carbon isotope composition in our data. This indicates that a coordinated plant response modified these parameters simultaneously across different altitudes. Around 2,800 m altitude there seems to be an optimum zone for growth and development of Q. aquifolioides, as indicated by thinner leaves, larger stomata and more negative d13C values. All available evidence indicates altitudinal gradients may have influenced the genetic variation pattern of Q. aquifolioides to some extent. Decreasing genetic variation and increasing genetic differentiation with altitude was obtained except for the WL1 population. And the environment of habitats and human disturbances were also contributing factors, which impact genetic variation pattern, especially to the low-altitude WL1 population.

四川九顶山西坡及龙肘山维管植物区系和植物多样性研究

横断山地区是一个十分自然的植物区系地区，在中国植物区系分区中是作为泛北极植物区中国-喜马拉雅亚区中的一个地区，其种子植物区系具有丰富的科、属、种，地理成分复杂，特有现象和替代现象明显。该地区作为植物区系和生物多样性的研究热点地区，长期以来极受中外植物学家关注。横断山脉东缘是中国-喜马拉雅和中国-日本植物区系的交汇过渡区域，北部的岷江流域以及南部的金沙江流域，孕育了该区丰富的物种资源和植被资源。而岷江干热河谷和金沙江干热河谷的相似性和相关性，更为该区的植物区系和生物多样性南北的对比研究提供了有利的条件。 本研究选择的九顶山西坡和龙肘山分别位于横断山区北部和南部，九顶山属岷江流域而龙肘山属金沙江流域。本研究结合植物区系研究和生物多样性研究，对该区的植物资源进行调查。通过样带调查和样线踏查结合，大量详实的野外样方调查和标本采集，进行传统的区系研究和生物多样性研究。研究该区物种多样性的海拔梯度格局及其潜在的影响影子，并利用新的区系评估质量方法对九顶山西坡的植物区系质量进行定量的研究，以期能更为深刻的理解该区的植物资源，为该区的资源保护和利用提供合理可行的建议。主要研究结论如下： 1）九顶山西坡植物区系的性质和特点 经鉴定和统计，九顶山西坡共有1707 种维管植物，分属617 属和140 科,其中种子植物1616 种，分属572 属117 科。就科的分布区成分构成而言，该区系的热带成分与温带成分相当，热带成分略占优势，表明九顶山西坡的植物区系与热带植物区系有较强的联系。但是，在九顶山西坡属的分布区类型所占的比例上，温带成分远远超过了热带成分，本区的种子植物分布表现出明显的温带性质。且温带分布类型的许多物种组成了九顶山西坡植被的建群种和优势种，是本区系最重要的成分，充分体现了本区系的温带性质。 2）九顶山西坡不同植被带的生物多样性海拔梯度格局 基于对土门-断头崖、茶山-九顶山、雁门沟-光光山三条垂直植被样带的调查，我们发现九顶山西坡的生物多样性沿海拔梯度的变化呈现出一定的规律性，不同样带之间有一定差异。就三条样带的物种组成相似性来看，虽然土门－断头崖样带属于涪江水系，而茶山－九顶山样带和雁门沟－光光山样带属于岷江水系，但不同水系对该区物种组成的影响并不明显。三条样带中，草本层物种丰富度均远远大于灌木层和乔木层，而以乔木层物种丰富度最低；α－多样性指数随着海拔梯度的变化在土门-断头崖样带中呈现单一下降趋势，在茶山-九顶山样带表现为双峰模型，而在雁门沟-光光山样带则表现为不显著波动变化；均匀度指数在土门-断头崖样带呈现出单一下降的趋势，在雁门沟-光光山样带表现为凹形曲线，而在茶山-九顶山样带却无明显的变化规律。β－多样性指数在土门-断头崖样带和茶山-九顶山样带呈现出明显的波动状态，植被类型替代现象明显；而在雁门沟-光光山样带却并未有十分显著的转折点，因其水平植被带受到干扰，同海拔替代现象不显著。 3）九顶山西坡维管植物丰富度的海拔梯度格局 我们考察了九顶山西坡和两条垂直样带（土门－断头崖和雁门沟－光光山样带）的不同分类等级（包括科、属、种）和不同生活型物种（乔木、灌木、禾草、蕨类和其它草本）的丰富度沿着海拔梯度的分布。结果发现，物种的丰富度海拔梯度格局具有不同的模式，单一下降和中间膨胀格局依然是其主流。不同生活型的物种具有不同的丰富度格局，但是对于环境需求相似的类型具有较相似的丰富度格局。不同的丰富度格局可能由多因素导致，包括：气候，海拔跨度，面积，人为干扰等等。 4）九顶山西坡区系质量评估 我们尝试使用传统的区系质量评估方法对九顶山西坡的区系质量进行评估，并尝试使用一种新的区系质量评估体系对该区的区系进行评价。在九顶山西坡随着海拔梯度的上升，平均保守性系数在各条植被带中均呈现出逐渐上升的趋势。区系质量指数随着海拔的升高都表现为双峰模型，在植被交错区区系质量指数相对较高，而在海拔的两极，区系质量指数都很低。大部分地区使用新方法计算所得的加权平均保守性系数和区系质量指数都比传统方法计算的平均保收性系数和区系质量指数要高，说明在九顶山西坡的三条样带中，大部分地区都是那些保守性系数较高的物种占据优势，同时也表明九顶山西坡具有很高质量的区系和自然植被。 5）龙肘山种子植物区系的性质和特点 龙肘山种子植物区系的物种较为丰富，共有154 科，544 属，1156 种。科的优势十分明显，单种属和寡种属数量众多，说明本区系植物成分较为复杂、起源古老、物种多样性指数较高。地理成分复杂，分布类型多样，其中热带成分在总数量上高于温带成分，但是许多温带成分的属是该区植被的重要建群类群和优势类群，表现出明显的亚热带性质。 6）龙肘山生物多样性的现状和特点 在海拔梯度上，龙肘山地区无论是科、属、种的数量，还是不同等级分类单元之间的数量比，均呈现先升后降的趋势，并在中海拔地区达到峰值。物种多样性指数从总体上来说变化幅度不大，略有先升后降的趋势，在中海拔梯度物种多样性最高。乔、灌、草三层的多样性指数表现出乔木层<灌木层<草本层的特征；乔木层均匀度的变化很大，而灌木层和草本层均匀度的变化较小；灌木层均匀度的波动又强于草本层。β－多样性指数呈现单峰模式，中海拔地区最高。就龙肘山东、西坡物种多样性相比较而言，两者虽然在数值上交替上升，但是却体现出了较为一致的趋势，但西坡因受到干热河谷气候的影响，其平均气温要高于东坡，导致了东坡植物群落和物种的分布比西坡要低。在区系成分构成上，低山区的相同海拔段，西坡的热带亚热带成分所占的比例要比东坡高，这是因为西坡的平均气温比东坡稍高，导致了热带、亚热带物种分布更多。而随着海拔的上升，东、西两坡的气候、土壤等条件趋于一致，其植物区系成分的构成格局也趋于一致。 The Hengduan Mountain region is a very natural floristic region; it belongs toChina-Himalaya sub-region of Holarctic region in floristic subarea of China. The flora in this areais rich in family, genus and species; has a very complex composition of geographical elements;especially with high richness of endemic species and obvious substitution phenomenon. Thisregion as a hot-spot area of floristic and biodiversity, has fascinated biologists in the world for along time. The eastern range of Hengduan Mountain is the transition zone of China – Himalayaforest sub-region and China-Japan forest sub-region in floristic. The water systems are quitedifferent, Minjiang River in the north and Jishajiang River in the south grow quit different but alsoabundant plant species and vegetation resources. The similarity and correlativity of Minjiang River dry valleys and Jinshajiang River dry valleys have provided advantageous condition tocontrast flora and biodiversity between north and south. In the present study, the Jiuding Mountainlies in the north of Hengduan Mountain and belongs to Minjiang River, and the LongzhouMountain lies in the south of Hengduan Mountain and belongs to Jinshajiang River. In our study, we combined the methods of floristic research and biodiversity investigation toexplore the resources of plant species and vegetations; sampled with transects along the altitudinalgradients and also with transverse straps with similar elevation; collected the vascular plant specimen with sampling plots of ecology. We explored the plant species richness patterns alongaltitudinal gradients and discussed the underlying factors aroused these patterns; and used a novelmethod to assess the quality of Jiuding Mountain’s flora. All for a deeper comprehension of the plant recourses of this region; and provided feasible and reasonable suggestion for the protectionof resources. The results were as follows: 1 The characteristic of the flora of the west slope of Jiuding Mountain We had collected 1707 species of vascular plants belonging to 617 genera in 140 families inthe west slope of Jiuding Mountain，in which included 1616 seed plant species belonging to 572genera and 117 families. As for the composition of the areal types of the Families of seed plants,tropic components and temperate components are well-balanced, and percentage of tropicscomponents is higher than that of temperate ones for a litter bit. This shows the flora in the westslope of Jiuding Mountain has strong relationship with the tropic flora. But for the composition ofthe areal types of genera, temperate components have far exceeded the tropics ones, indicated thewhole flora with a conspicuous temperate character. Temperate components possess maximumproportion in the west slope of Jiuding Mountain, and many of them belong to constructivespecies and dominant species in the vegetation, are most important components in JiudingMountain’s Flora, also have embodied the temperate character of this area sufficiently. 2 Biodiversity patterns along altitudinal gradients in different vegetation transects in the westslope of Jiuding Mountain Based on the investigation of three vegetation transects (including Tumen-Duantouya transect,Chashan-Jiudingshan transect and Yanmengou-Guangguangshan Transect) in the west slope ofJiuding Mountain, we found the change of biodiversity along the altitude gradients displayedcertain regularity, but have differences among different transects. The three transects belong todifferent water systems; the Tumen-Duantouya transect belongs to Fujiang River, and the othertwo belong to Minjiang River. From the similarity of species compositions of different transects,we found different water system didn’t show obvious impact on the species composition. In all thethree transects, the species richness of herb layer was remarkably higher than shrub and tree layer,and the species richness of tree layer was the lowest one. With the increasing of the altitude, theline of α-diversity was monotonically decreasing curve in Tumen-Duantouya transect, andbimodal curve in Chashan-Jiudingshan transect, but in Yanmengou-Guangguangshan transectshowed a wave-like curve although not very obvious. Species evenness showed monotonicallydecreasing trends in Tumen-Duantouya transect, and very low at mid-altitude in Yanmengou-Guangguangshan transect, but in Chashan-Jiudingshan transect changed irregularly. Changes inβ-diversity corresponded with the transition of vegetation in the Tumen-Duantouya transect andChashan-Jiudingshan transect, and the curve of β-diversity along altitude had obvious turningpoint; but in Yanmengou-Guangguangshan transect had no obvious turning point, and thesubstitution phenomenon was not obvious, transverse vegetation straps distributed interlaced. 3 Richness patterns of vascular plant species along altitude in the west slope of Jiuding Mountain Direct gradient analysis and regression methods were used to describe the species richnesspatterns along the altitudinal for Mt. Jiuding, as well as separately for Tumen-Duantouya Transectand Yanmengou-Guangguangshan Transect. Altitudinal gradient of diversity of units at differenttaxonomic level (including Family, Genus and Species) and at different life form (including tree,shrub, pteridophyte, grass and other herb) were tested to find differences among the richnesspattern. We found altitudinal richness also shows different patterns, and both monotonicallydecreasing pattern and hump-shaped pattern can be founded in vascular species richness. Speciesin different life forms show different altitudinal patterns, but those species with similarrequirements to environmental conditions show similar richness patterns along altitudinalgradients. Different richness patterns can be aroused by different climate, different altitudinal span,area factor, anthropogenic factor and so on. 4 Floristic quality assessments in the west slope of Jiuding Mountain We used both the conventional method broadly adopted in the USA and the new one toassess the floristic quality in the west slope of Jiuding Mountain. The Mean Coefficient ofConservatism (MC) had the trend of increment along the altitudinal gradients. The FloristicQuality Index (FQI) was a bimodal curve with increasing of elevation; FQI got maximum valuesin the transition zones of different vegetations in the middle altitude, and had very low values atthe two end of elevation. In most areas of the west slope of the Jiuding Mountain, the resultscalculated using the new methods were higher than those using the conventional method. Thisindicated the dominant species of the communities had very high coefficients of conservatism inmost areas of Jiuding Mountain, and the communities are relatively kept pristine and the habitats very integrative. 5 The characteristic of the flora of Longzhou Mountain The flora of Longzhou Mountain has very abundant in species composition; there are about1156 species of seed plants belonging to 544 genera in 154 families. In which, twelve families with more than 20 species include totally 232 genera and 532 species, and form the majority of itsflora. The origin of its flora is old, monospecific genera and oligotypic genera amounts to 510 innumber, which constitute 93.75% of total number of genera. The geographical components arevarious in Longzhou Mountain, the majority of flora are temperate and pantropic ones. The tropiccomponents overtopped temperate components on genera quantity, but many temperatecomponents belong to constructive species and dominant species in the vegetation, and the wholeflora shows an obvious subtropical character. 6 Current situation and characteristic of biodiversity in Longzhou Mountain With the increasing of altitude, the number of species, genus, family and the ratios ofdifferent taxonomic levels all displayed a trend of descending after rising first, and peaked atmiddle height area. The change of α-diversity was not very acutely, with the trend of descendingafter rising first in some degree, the middle height area had highest α-diversity. As studying thetree layer, shrub layer and herb layer respectively, the Shannon-Wiener index was in followingorder: tree layer < shrub layer < herb layer; the change of evenness was more complicatedly thanthat of diversity, the tree layer changed acutely, but the shrub layer and herb layer fluctuatedsmoothly. Changes in β-diversity also showed the trend of descending after rising first. TheJaccard index and Cody index all peaked at the middle height forest area. As for the comparison ofplant diversity and evenness between the west and east slope, the numerical values ascendedalternatively, but the trend of changing was similar. The distribution of similar plant communitiesand species in east slope were lower than the west slope for the influence of Jinsha River DryValley. As for the composition of different floristic components, in lower altitude area of westslope, the tropic and sub-tropic plants had higher ratio than east slope’s and even could be equal tothe temperate plants. With the increasing of elevation, the floristic composition become morelikely between the east and west slope and temperate plants dominated the flora.

Range change in Metasequoia: relationship to palaeoclimate

IEECAS SKLLQG

Range-based attacks on links in random scale-free networks

Range and load play key roles in the problem of attacks on links in random scale-free (RSF) networks. In this paper we obtain the approximate relation between range and load in RSF networks by the generating function theory, and then give an estimation about the impact of attacks on the efficiency of the network. The results show that short-range attacks are more destructive for RSF networks, and are confirmed numerically.