缙云山草珊瑚(Sarcandra glabra)天然居群结实特征的变异性研究

对缙云山草珊瑚8个天然居群结实特征的20项表型性状的变异性进行了研究,结果表明:各表型性状在居群内与居群间都存在很大的变异性,其中种实产量、果序数和果序分枝的变异程度较高,而果实和种子的特征指数变异程度较低,同类性状果实的变异程度要大于种子;平均变异系数最大的性状是四分枝果序百分比(1.477),最小的是种子长宽比(0.041);变异程度最大的居群是居群6(0.564),最小的是居群4(0.292);各居群间除果序分枝总数差异不显著、果序数和二分枝果序百分比差异显著外,其它17项表型指标均达到极显著水平,表明缙云山草珊瑚各居群间已经发生了明显的形态分化;居群内和居群间变异分别占总变异的60.7%和39.3%,说明居群内变异是表型变异主要来源,但居群间变异也不容忽视;欧氏距离聚类将所有居群划归为两大类群,主要与居群的群落类型与干扰程度有关;表型性状的Pearson相关性聚类显示草珊瑚同类性状在表型分化过程中具有很强的相关性。     

北京东灵山地区不同海拔柴胡居群的遗传多样性

利用ISSR技术对北京东灵山地区不同海拔的6个柴胡居群进行分析,观察不同海拔柴胡居群的遗传多样性。结果表明,东灵山地区不同海拔柴胡居群的遗传多样性差异较大,海拔1135m居群表现出较高的遗传变异水平,高海拔居群遗传多样性较低;遗传距离与海拔差距有一定的相关性,相邻海拔的不同柴胡居群间具有相对较低的遗传距离;柴胡具有较强的遗传分化趋势,且大部分变异存在于居群内。不同海拔导致的异质生境及基因流是影响柴胡居群遗传多样性的主要原因。     

基于形态及分子标记的濒危植物夏蜡梅自然居群的遗传变异研究

比较了濒危植物夏蜡梅(Sinocalycanthus chinensis)大明山、大雷山、龙须山3个居群的果实与种子的形态变异,采用ISSR分子标记技术分析DNA序列的变异,综合评价夏蜡梅3个居群的遗传变异。结果如下:果实性状中,果柄长、果实长、果实重、每果种子数等指标均以大明山居群最大、大雷山居群次之、龙须山居群最小,它们之间差异显著(P<0.05)。种子重、种子长、种子宽、种子厚等指标均以大雷山居群最大,与大明山居群和龙须山居群差异显著(P<0.05)。基于果实形态特征的表型分化系数(VST)在0.5518—0.9750之间,平均为0.8930,所有果实形态指标的变异大部分存在于居群间。基于种子形态特征的VST在0.1669—0.8678之间,平均为0.6240,除种子长外,其他种子形态指标的变异也大部分存在于居群间。ISSR分析表明,3个居群的多态位点百分率、Shannon信息指数、Nei基因多样性均是大明山居群最高、龙须山居群次之、大雷山居群最低。居群间的遗传分化系数(GST)为0.6050。基于ISSR分子标记数据的聚类结果显示大明山居群先与龙须山居群聚在一起,再与大雷山居群相聚,这与基于种子性状特征的聚类结果相似,而与基于果实性状特征的聚类结果不同。3个居群的种子形态特征变异系数与遗传多样性水平具有显著的正相关,且基于果实形态特征估算的VST要高于GST,而基于种子形态特征估算的VST仅略高于GST,表明夏蜡梅不同居群间的种子形态变异主要由遗传变异所造成的,而环境因子在果实形态变异中起了重要作用。Mantel检验显示3个居群基于分子标记数据的遗传距离矩阵和基于果实及种子形态特征的欧氏距离矩阵之间的相关性不显著,表明果实与种子在居群间出现的表型分化除了受遗传因素影响外,还受到其它环境因子的强烈影响。     

濒危植物金花茶果实、种子形态分化

对濒危植物金花茶5个天然居群和1个人工居群的果实、种子形态进行了研究.结果表明:6个金花茶居群按果实、种子大小进行排序为:广西植物所(GXIB)＞那子山中海拔2(NZSH2)＞大王江(DWJ)＞庚毛山(GMSH)＞那子山高海拔3(NZSH3)＞那子山低海拔1(NZSHI);表型性状在居群内和居群间均存在一定程度的变异,不同形态性状在居群间变异系数的平均值从0.429(种子质量/果,SWPF)到0.069(果实整体形态,FT/FD),果实整体形态最为稳定,各居群形态性状变异系数的平均值从0.287(NZSH3)到0.155(GXIB)不等;在调查的15个性状中,果实直径、果实质量等3个性状在居群间的差异达到显著水平(P＜0.05),种长、种宽等7个性状在居群间的差异达极显著水平(P＜0.01),多数居群已产生较明显的形态分化;聚类分析结果表明,在居群水平上,形态分化并不与居群间的地理距离远近相关联.影响果实、种子表型性状变异的主导因子为海拔高度、土壤有机质、土壤含水量和乔木层透光率.     

骆驼蓬属种子微形态及其生态学与分类学意义

报道了光及扫描电镜下,西北地区骆驼蓬属３种,９个地方居群的种子微形态特征。结果表明：该属植物种子微形态特性在种的水平上具有分类学意义,同种的不同地方居群间基本类型一致,但也存在一定程度的变异。其种子微形态与萌发有关。     

油松天然群体的种实性状表型多样性研究

为了揭示油松天然种群在不同地理环境条件下表型变异的程度和规律,在油松整个天然分布范围内选择了12个具有代表性的居群作为研究对象,对其球果、种子、种翅等12个种实性状的变异程度及其与环境因子间关系进行了比较分析。结果显示:(1)各个性状在居群内和居群间均存在较大的变异(CV>12%)。其中千山(QS),曾家镇(ZJ)和互助(HZ)3个居群表现出了较高的变异(CV>20%),而球果干重(CDW)和种子长(CL)是所有表型性状中变异幅度最大的(CV分别为31%和21%),但种翅性状与其他性状相比具有较高的稳定性。(2)巢式设计方差分析表明,在居群内表型分化系数(Vst)变化在3.18%~89.86%之间,而群体间的Vst为38.97%;与其他针叶树种相比,油松拥有较高的表型分化系数,且居群内的变异程度远高于居群间的变异,尤其是千山(QS)、曾家镇(ZJ)和互助(HZ)3个居群,这说明油松具有较高的环境异质性适应能力或恶劣环境耐受能力。(3)相关性分析表明,该研究的各形态特征与潜在蒸发量均为负相关,且大部分形态指标间及它们与潜在蒸发量间存在显著相关性,表明潜在蒸发量是油松形态特征变化的最重要环境影响因子,预示油松最适宜生长于温暖潮湿的环境中;并表明因各形态特征间相互紧密关联,所以它们受环境条件影响而共变。     

东兴金花茶表型变异研究

对东兴金花茶(Camellia tunghinensis Chang)5个自然居群的表型变异特征进行研究。结果表明：东兴金花茶多数表型指标居群间变异大于居群内变异;20项表型指标中,果柄粗(FHT)、果实横径(FD)、果实纵径(FT)和果实重量(FM)等13项指标在居群间的差异达到了极显著水平(P<0.01),其中,种子重量百分比(SMPF/FM)的变异程度最大,而种宽(SB)的变异程度最小;表型总体在居群间的差异未达到显著水平;按变异系数均值大小,5个居群的排列顺序为SFSH1 (0.272)＞MJG (0.217)＞SFSH (0.207)＞SHL (0.190)＞DGL (0.170);平均株高、植株基径与各表型性状间的相关性不显著;不同表型性状间存在一定的相关性。     

蒙古冰草外稃微形态特征的变异式样

采用电镜扫描技术对蒙古冰草（Agropyron mongolicum Keng)6个天然居群和2个栽培品种的外稃进行了观察分析。结果表明,外稃的微形态特征存在有14种变异类型,具有丰富的多态性;从这些变异的分布格局来看,主要存在于居群内的个体间,居群间的分化并不明显,反映出了居群内变异大于居群间变异的特点。     

内蒙古中部地区小叶锦鸡儿天然居群表型多样性分析

对采自内蒙古中部地区的7个小叶锦鸡儿(Caragana microphylla Lam.)天然居群的207份材料进行了表型多样性分析.结果表明:小叶锦鸡儿种内表型性状存在丰富的变异,无论在居群间还是在居群内均表现出极显著差异(P<0.001);叶片、荚果、种子等11个表型性状居群间分化系数为16.90%,居群内表型性状分化系数为83.10%,是小叶锦鸡儿表型变异的主要来源;主成分分析显示荚果柄长、荚果长、关节长是造成小叶锦鸡儿表型变异的主要影响因子;依据小叶锦鸡儿表型性状,通过聚类分析将7个小叶锦鸡儿居群分为3类,第1类为多伦居群,第2类为西乌旗居群,第3类为四子王旗、察右后旗、化德、镶黄旗和正镶白旗5个居群.     

内蒙古东部地区小叶锦鸡儿表型变异研究

根据小叶锦鸡儿(Caragana microphylla Lam.)资源分布状况,对内蒙古东部地区的13个小叶锦鸡儿天然居群进行表型变异研究。结果表明：小叶锦鸡儿表型性状在居群间均表现为极显著差异（p<0.001）;主成分分析显示种子宽、种子长、荚果长是小叶锦鸡儿表型变异的最主要影响因子;回归分析和偏相关分析显示地理生态因子对小叶锦鸡儿的表型变异有较强的影响;通过聚类分析将13个小叶锦鸡儿居群分为3类。     

毛乌素沙地锦鸡儿（Caragana）种群形态变异

以柠条锦鸡儿（Ｃａｒａｇａｎａｋｏｒｓｈｉｎｓｋｉｉ）人工种群为对照,研究了自然分布在内蒙古毛乌素沙地各类生境（硬梁、覆沙硬梁、覆沙软梁、覆沙滩地和沙丘）的９个锦鸡儿种群的具分种意义的形态特征的变异。荚果长度在一个植株内是比较稳定的性状;但在各个种群内、种群间变异很大,覆盖了小叶锦鸡儿（Ｃ．ｍｉｃｒｏｐｈｙｌｌａ）、中间锦鸡儿（Ｃ．ｉｎｔｅｒｍｅｄｉａ）和柠条锦鸡儿３个种的范围。同一生境不同种群以及不同生境种群的比较,说明,．决定荚果长度的主要是遗传因素,环境因子如水分条件可能只起次要作用。每个自然种群荚果长度的分布出现几个峰值,说明种群遗传组成的异质性。小叶形状和被毛的资料也说明各个种群内和种群间的异质性。看来,该地区锦鸡儿是上述３种锦鸡儿的杂种带（Ｈｙｂｒｉｄｚｏｎｅ）．形态变异资料也说明毛乌素沙地在遗体多样性方面也是生态过渡带。     

ALTERNATIVE ROUTES TO THE EVOLUTION OF COMPETITIVE ABILITY IN TWO COMPETING SPECIES OF DROSOPHILA

The evolution of components of interspecific competitive ability was examined in three different environments for three replicate pairs of Drosophila melanogaster and D. simulans populations. Populations evolved enhanced competitive ability in three ways: (1) increased effectiveness at reducing the numbers of the competitor species; (2) increased resistance to the inhibitory effects of the competitor species; or (3) a combination of the two. Considerable variation was seen in the evolutionary outcomes of competition among environments, and also among replicate populations within environments. Significant replicate-by-environment interactions were also observed. The results suggest that the evolutionary routes to the evolution of enhanced competitive abilities can potentially differ among subdivided populations, creating a geographic mosaic of outcomes.     

VARIATION IN LEAFLET MORPHOLOGY AMONG POPULATIONS OF CARIBBEAN CYCADS (ZAMIA)

Caribbean cycads (Zamia L.) are well known for variation in leaflet morphology. Here, I examine the variation in leaflet morphology among five populations of Zamia in Florida. Variables measured were leaflet length and width, leaflet length: width ratio, leaflet surface area, rachis and petiole lengths, number of leaflets per leaf, and total leaf area. In addition to comparisons among the Florida populations, these populations are compared with three previously studied populations in Puerto Rico (Newell, 1986). For the most part, the populations exhibited significant differences in all variables. In spite of the extensive morphological variation in this group of plants, leaflet morphology has long been important in Zamia taxonomy. The Florida populations would be considered by some to be either one, two, or three different species. The Florida and Puerto Rico populations together might be considered as few as one species or as many as five species. Based upon the data presented here, the five Florida populations appear to represent a single species; and the three Puerto Rico populations appear to represent two additional species. Further clarification of the taxonomy of Caribbean Zamia will require additional characters such as cone morphology and protein or DNA patterns.     

Variation in nectar volume and composition of Impatiens capensis at the individual,plant, and population levels

Although the volume and chemical composition of nectars are known to vary among plant species and to affect pollinator response to plants, relatively little is known of the variation in volume, and sugar and amino acid composition within species. We collected nectar from Impatiens capensis in a nested design: three flowers from each of three plants from each of three populations. This design enabled us to quantify variation within individual plants, among plants within populations, and among populations. Using high performance liquid chromatography, we analyzed the sugar and amino composition of the 27 flowers. Analysis of variance showed that none of the parameters (volume, concentrations of three sugars and 24 amino compounds) varied within individuals. Variation in nectar volume was not significant among plants but was nearly significant among populations. Of the three sugars detected (sucrose, glucose, and fructose), the only significant variation was that of sucrose among populations. Concentrations of 12 amino compounds varied significantly at the plant level while 7 amino compounds varied among populations. The results indicate that: (1) pooling of nectar samples from flowers of individual plants can be an acceptable methodology for those seeking to understand within species variation; (2) amino compounds appear to vary more than either volumes or sugar concentrations; (3) future studies should assess how much of the observed variation is due to genetic versus environmental differences; (4) additional studies should examine the geographic variation in nectar parameters and pollinators of I. capensis in order to assess the role different pollinators play in shaping nectar composition.     

GENETIC STRUCTURE OF POPULATIONS OF GEOGRAPHICALLY RESTRICTED AND WIDESPREAD SPECIES OF ASTRAGALUS (FABACEAE)

Evolutionary theory predicts that species with small ranges and few individuals will exhibit low levels of genetic polymorphism. We investigated the population genetic structure of two locally endemic and two geographically widespread species of Astragalus. To facilitate direct comparisons among these congeners, three populations of each species were sampled in a consistent manner and scored for allozyme polymorphisms at 12 loci. Genetic polymorphism was lower in restricted A. linifolius and A. osterhouti than in widespread A. pectinatus. However, the restricted species do exhibit a moderate level of isozyme variation, comparable to that of widespread A. pattersoni and higher than has been detected in several other rare plant taxa. As measured by Wright's F statistics, there were no consistent differences between the restricted and widespread taxa with respect to the organization of genetic variation. F_ST values were low in all taxa, indicating little heterogeneity among populations.     

TESTING MODELS OF MIGRATION AND ISOLATION AMONG POPULATIONS OF CHINOOK SALMON (ONCORHYNCHUS TSCHAWYTSCHA)

The chinook salmon (Oncorhynchus tschawytscha) is a behaviorally, morphologically, and ecologically variable species distributed over a large geographic range. Although previous genetic surveys have revealed considerable genetic differences among populations with different life history types and from different major river drainages, it is not clear to what degree these genetically distinct populations are connected by low levels of gene flow. The work described in this paper addresses this question by surveying DNA restriction site variation at six nuclear genes from nine populations encompassing most of the species's North American range, and then attempting to fit the patterns of variation observed at these genes to five different evolutionary models using computer simulations of the coalescent process. Two commonly used constant population size models, one hypothesizing no migration among populations and one hypothesizing equal rates of migration among populations, were found to be statistically inconsistent with the observed patterns of variation. The other three models, which involved either recent divergence among populations coupled with large changes in populations size, unequal migration rates among populations, or selection, were all found to be consistent with the observed patterns of variation. Assuming selective neutrality, these results suggest that either the populations have all descended from a common ancestral population within the last ~50,000 years and have all suffered large declines in effective population size since that time, or that they have a more ancient divergence time but are connected by low levels of gene flow. These conclusions rest on the assumption of selective neutrality. With the methods employed, it was not possible to simultaneously test hypotheses of both selective neutrality and population structure.     

QUANTITATIVE VARIATION IN PHLOX: COMPARISON OF SELFING AND OUTCROSSING SPECIES

Variation of 20 quantitative characters was examined within and among 10 populations of the predominantly outcrossing Phlox drummondii and 4 populations of the predominantly selfing P. cuspidata grown in a greenhouse. Multivariate analysis of variance, considering all characters simultaneously, indicated that there were significant differences among populations in both species while analysis of individual characters demonstrated that there were significant population differences for 19 characters in P. drummondii and 13 characters in P. cuspidata. On average, 16% of the total phenotypic variation in P. drummondii occurred among populations compared to less than 4% of the total variation in P. cuspidata. In addition, P. drummondii exhibited significant differences among families within populations more frequently than P. cuspidata. Most observed variation in both species occurred within families where environmental and genetic sources of variation could not be partitioned. There was a trend for P. drummondii to have higher heritabilities than P. cuspidata for most characters even when assumptions about breeding systems were relaxed. Thus, the outbreeding species exhibited larger genetic differences among populations and among families within populations than the selfing species in the greenhouse environment. These data suggest that P. drummondii has the greater evolutionary potential of the two species and are consistent with the hypothesis that differences in population structure result from differences in the breeding systems of the two species.     

ANALYSIS OF MECHANISMS OF MICROEVOLUTIONARY CHANGE IN CEPPHUS GUILLEMOTS USING PATTERNS OF CONTROL REGION VARIATION

We surveyed population-level sequence variation in part of the mitochondrial control region for three species including eight subspecies of Cepphus guillemots (Charadriiformes: Alcidae) to test specific predictions about mechanisms of population differentiation. We found that sequences of spectacled guillemots (C. carbo) were more closely related to those of pigeon guillemots (C. columba; both found in the Pacific Ocean) than to those of black guillemots (C. grylle; Arctic and Atlantic Oceans), despite dissimilarities in plumage between spectacled guillemots and the other species. Distributions of species and timing of divergence events suggest that speciation involved allopatric and microallopatric populations isolated by Pleistocene glaciers. Control region sequences were significantly differentiated among populations within species and suggest that gene flow is low; however, populations are probably not in genetic equilibrium, so these results probably reflect historical isolation of colonies. In contrast, phylogenetic relationships among sequences within species were poorly resolved, probably because of a combination of incomplete lineage sorting and contemporary gene flow. Indices of genetic diversity provided no suggestion of recent bottlenecks in most populations, although two populations apparently underwent recent severe bottlenecks. Genetic divergence among populations was not correlated with geographic distance, which argues against isolation by distance. Results of these analyses, combined with breeding distributions and timing of divergence events, suggest that populations diverged during isolation in glacial refugia. Our results are consistent with earlier hypotheses posed by Storer and Udvardy.     

INTER- AND INTRASPECIFIC VARIATION OF MOSSES IN TOLERANCE TO COPPER AND ZINC

Bryophytes are often viewed as slowly evolving with little genetic variation within and among populations. A study of heavy-metal tolerance was initiated to test the capacity of bryophytes to undergo genetic differentiation in response to natural selection. Tolerance of Funaria hygrometrica to copper and zinc was greater in populations that originated on soil with high concentrations of these metals. Protonemal growth was more inhibited by the metals than was germination, and copper was more toxic than zinc. Zinc and copper tolerances were correlated, but so were the zinc and copper concentrations of native substrates. The pattern of population differentiation for heavy-metal tolerance in this species is much like that of flowering plants. Five populations of Physcomitrium pyriforme, which does not occur on metal-contaminated soil, were all highly tolerant of zinc but extremely intolerant of copper. This species seems to have an inherent tolerance to the former. Significant variation in tolerance to copper and zinc occurred among populations, but tolerance did not correlate with metal contents in native substrates. This pattern differs from that of flowering plants. Normal populations of species that colonize contaminated sites tended to be more tolerant than populations of species that do not colonize such sites. The extensive population differentiation in Funaria hygrometrica augments the evidence from electrophoretic data that there is genetic variation among populations of mosses and liverworts.     

濒危植物独花兰的形态变异及其适应意义

采用ANOVA和UPGMA等方法对濒危植物独花兰(Changnieniaamoena)分布于庐山、新宁和神农架3个地点的12个自然居群的形态变异进行了研究,探讨其形态多样性水平和地理变异式样及其可能的适应机制。结果表明,庐山居群13个性状的平均观测值均高于新宁和神农架居群。在物种水平上各个性状存在较丰富的变异,变异系数(CV值)为0.02–0.30。尽管同一性状在不同居群中的变异程度较大,但总体而言,花部器官的变异性比营养器官低。单因素方差分析显示3个地区间多个形态性状存在极显著差异(P<0.01);UPGMA聚类分析也表明这3个地区分别形成明显不同的分支。值得注意的是,神农架地区龙门河和关门山两个地点间存在明显的形态分化,而这种形态分化是以传粉者为媒介自然选择的结果。相关性分析显示,营养器官之间、花部器官之间,以及营养器官与花部器官之间均存在较高的相关性。上述结果对进一步了解独花兰的适应机制以及制定科学的保护策略提供了有益的资料。