油松种群不同龄级的空间格局与关联性分析

在霍山七里峪林场,选择典型油松林样地进行实地调查,运用点格局分析方法,对油松种群不同龄级的分布格局及其相互关系进行了研究。结果表明：(1)油松的龄级分布呈峰型,中间龄级个体多,主要集中在20～30 cm,小龄级和大龄级则相对较少;(2)油松的7个龄级个体的空间格局呈集群分布,其中龄级4、龄级5和龄级6的个体集群分布特征更为明显,同时表现出小尺度下呈集群分布,在大尺度下趋向于随机分布;(3)各龄级间的关系基本上呈显著正关联,3～5龄级的个体间正关联性更强,这种正关联的关系有利于油松种群对资源的充分利用,以确保种群的生存和发展。     

不同尺度下野大豆种群的遗传分化

为了阐明不同尺度范围内野大豆种群的遗传分化情况,应用随机扩增多态性DNA（RAPD）方法,分别对我国5个纬度8个不同地点的野大豆（Glycine soja)种群及浙江金华地区5个野大豆种群,进行了分子生态学研究。根据RAPD数据计算相似系数及遗传距离并进行聚类分析,发现无论是不同纬度野大豆种群还是金华地区野大豆小种群均存在较高的遗传变异,且不同纬度野大豆种群间的遗传变异与地理纬度有一定正相关。在对金华地区野大豆种群遗传多样怀的研究,利用Shannon指数估算了5个野大豆种群的遗传多样性,发现大部分的遗传变异存在于野大豆种群间（78．5％）,只有少部分的遗传变异存在于种群内。本就此探讨了不同尺度下野大豆种群的遗传多样性与环境因子的关系,并对其成因及维持机制进行了讨论。     

利用SSR分子标记分析秦岭冷杉自然居群的遗传多样性

利用10对SSR引物对濒危植物秦岭冷杉(Abies chensiensis)6个自然居群的120个个体进行了遗传多样性研究,旨在分析秦岭冷杉6个自然居群的遗传多样性、遗传结构及基因流变化.研究结果表明,120个个体在10个位点上共检测到149个等位基因,平均每个位点的等位基因数(A)为14.9,每个位点的有效等位基因数(e)为7.7,每个位点的平均预期杂合度(He)和平均观察杂合度(Ho)分别为0.841和0.243,Shannon多样性指数(Ⅰ)为2.13,自然居群杂合性基因多样度的比率(FsT)为6.7％,居群间的基因流(Nm)为3.45.利用Mantel检测到自然居群的遗传距离与地理距离间无显著相关性(r=0.490 6,P＞0.05).秦岭冷杉自然居群的遗传多样性水平较低,遗传变异主要存在于居群内部.结合研究数据、实地调查及相关资料,推测秦岭冷杉自然居群间基因流较原来增大可能是因为居群间发生了远交衰退.     

不同天然居群小蓬竹的遗传多样性

从分子水平探讨不同居群小蓬竹的遗传多样性以及与环境因子的相关性,揭示其濒危原因,为小蓬竹的保护和后续开发利用提供理论支撑,助力实施极危物种最佳保护策略。运用RAPD标记技术和POPGENE32对16个小蓬竹天然居群进行遗传多样性研究和遗传变异分析。结果表明,8个RAPD随机引物共扩增出105条清晰、重复性高的条带,其中多态性条带有98条,分子量300~2000bp;物种水平多态性位点百分率PPL=93.33%,有效等位基因数Ne=1.4942,Nei’s基因多样性H=0.3005,Shannon多样性指数I=0.4586;落湾(ZY1)居群的遗传多样性水平最高(PPL=60.95%,H=0.2329,I=0.3451),[JP3]桃坡(PT1)居群的最低(PPL=44.76%,H=0.1700,[JP]I=0.2523);16个天然居群的遗传分化系数Gst=0.3231,基因流Nm=1.0478,基于Shannon’s多样性指数的分化系数[(HSP-HPOP)/HSP]为0.3429。小蓬竹居群内存在丰富的遗传多样性,各个天然居群间具有一定的遗传分化但分化水平并不高,主要的遗传变异存在于居群内部。     

Establishment and maintenance of adaptive genetic divergence under migration, selection, and drift

There is a long tradition in population genetics of exploring the maintenance of variation under migration-selection balance using deterministic models that assume infinite population size. With finite population size, stochastic dynamics can greatly reduce the potential for the maintenance of polymorphism, but this has yet to be explored in detail. Here, classical two-patch models are extended to predict: (1) the probability of a locally beneficial mutation rising in frequency in the patch where it is favored and (2) the critical threshold migration rate above which the maintenance of polymorphism is much less likely. Individual-based simulations show that these approximations provide accurate predictions across a wide range of parameter space.     

人类群体遗传空间结构的"克立格"模型

通过将“克立格”技术应用于人类群体遗传学领域,构建了人类群体遗传空间结构的“克立格”模型,并论述了其原理和计算方法。以HLA-A基因座为例,应用“克立格”模型,定量分析了中国人群HLA-A基因座的空间遗传异质性;对HLA-A基因频率的空间数据矩阵进行了主成分分析,进而定义了人类群体遗传结构的综合遗传测度(SPC),绘制了综合遗传测度和主成分(PC)的“克立格”地图,分析了其群体遗传空间结构特性。与其他空间插值或平滑方法相比,人类群体遗传空间结构的“克立格”模型具有明显优点：1)“克立格”估计以空间遗传变异函数模型为基础,在绘制空间遗传结构地图之前,可利用变异函数模型定量分析所研究基因座(或多基因座)的空间遗传异质性;2)“克立格”插值方法是真正意义上的无偏估计模型,它利用待估区域周围的已知群体遗传调查点数据,并充分考虑调查点的空间影响范围,给出待估区域的最优估计值;3)“克立格”模型允许估计插值误差,这种插值误差既可用于评价空间估计效果,又可通过绘制误差地图指导在误差过高的地点增加新的群体遗传调查样本点,以优化估计效果。然而,人类群体遗传空间结构的“克立格”模型也存在一定缺点：1)若不能用任何理论遗传变异函数模型拟合观察遗传变异函数值,则不能建立“克立格”模型;2)若理论遗传变异函数的拟合优度很低,则据此建立的“克立格”模型的估计标准差在整个空间范围内会很大,此时“克立格”模型不适用于估计群体遗传空间结构。出现上述两种情形时,应选用不考虑空间相关性的空间随机插值方法绘制群体遗传结构地图,如基因绘图软件中的Cavalli-Sforza方法,反向距离加权法和条样函数插值法等。     

Evaluation of the Umbrella Species Concept at Fine Spatial Scales

Declines in the spatial extent of the sagebrush ecosystem have prompted the consideration of conservation efforts that view the greater sage-grouse (Centrocercus urophasianus; sage-grouse) as an umbrella species at landscape scales. Conservation strategies that focus on an umbrella species, however, may have unintended negative consequences for co-occurring species at finer scales. In North America, grassland and shrubland songbird populations are declining faster than other avian groups. Conservation of sage-grouse habitats may protect songbird habitats where distributions overlap. To assess the umbrella species concept at fine scales, we quantified nest-site selection for a sagebrush-obligate songbird, the Brewer's sparrow (Spizella breweri). We then compared the fine-scale habitat variables that influenced Brewer's sparrow nest-site selection with fine-scale nest-site selection for sage-grouse in the Powder River Basin region of northeastern Wyoming, USA. We modeled nest-site selection using conditional logistic regression for Brewer's sparrow (2016–2017) and logistic regression for sage-grouse (2004–2007). Both species selected nest sites with higher visual obstruction, shrub height, and branching density, although the selection for higher shrub height was stronger for sage-grouse. Brewer's sparrows selected nest shrubs with higher percentage of living foliage (vigor), and the opposite was shown for sage-grouse. At the nest site, based on the variables we measured, our results suggest that Brewer's sparrows and sage-grouse select for similar habitat attributes, with the exception of shrub vigor of the nest shrub. The stronger selection for more vigorous shrubs in Brewer's sparrows may be because they nest in shrubs, rather than on the ground under shrubs (as in sage-grouse). Most of the conservation objectives for protection of sage-grouse habitats appear to be beneficial or inconsequential for Brewer's sparrow. Local habitat management for sage-grouse as a proxy for conservation of other species may be justified if the microhabitat preferences of the species under the umbrella are understood to avoid unintentional negative effects. © 2019 The Wildlife Society.     

大豆遗传图谱的构建和分析

利用大豆栽培品种科丰1号和南农1138－2杂交得到的重组近交系NJRIKY,通过RFLP,SSR,RAPD和AFLP4种分子标记的遗传连锁分析,构建了包含24个连锁群,由792个遗传标记组成的大豆较高密度连锁图谱,该图谱覆盖2320．7cM,平均图距2．9cM,SSR标记的多态性较高,在基因组中的位置相对稳定,可以作为锚定标记,有利于连锁群的归并和不同图谱的比较整合;而AFLP标记对于增加图谱密度效率较高,但其容易出现聚集现象,从而造成连锁群上有很大的空隙（gap),另外,在连锁群中有21．7％的分子标记出现偏分离,该图谱为基因定位,比较基因组学和重要农艺性状的QTL定位等研究打下了基础。     

Genetic Variation in Indian Populations of Scirpophaga incertulas as Revealed by RAPD-PCR Analysis

Scirpophaga incertulas, commonly referred to as yellow stem borer, is a predominant pest of rice causing serious losses in its yield. Genetic variation among populations of Scirpophaga incertulas collected from 28 hotspot locations in India was examined using the randomly amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR). In all, 32 primers were used and 354 amplification products were observed. No RAPD-PCR bands diagnostic to the pest population from any specific region were identified. Cluster analysis using UPGMA showed that, with the exception of the pest population from Pattambi, all the populations cluster as one group with GD values in the range of 6–22%, suggesting that gene flow between populations is independent of geographic distance and appears to be unrestricted. The relatively high GD value of 48% exhibited by the pest population from Pattambi was the only exception.     

Discrepancies in population differentiation at microsatellites, mitochondrial DNA and plumage colour in the pied flycatcher--inferring evolutionary processes

Genetic differentiation between three populations of the pied flycatcher Ficedula hypoleuca (Norway, Czech Republic and Spain, respectively) was investigated at microsatellite loci and mitochondrial DNA (mtDNA) sequences and compared with the pattern of differentiation of male plumage colour. The Czech population lives sympatrically with the closely related collared flycatcher (F. albicollis) whereas the other two are allopatric. Allopatric populations are on average more conspicuously coloured than sympatric ones, a pattern that has been explained by sexual selection for conspicuous colour in allopatry and a character displacement on breeding plumage colour in sympatry that reduces the rate of hybridization with the collared flycatcher. The Czech population was genetically indistinguishable from the Norwegian population at microsatellite loci and mtDNA sequences. Recent isolation and/or gene flow may explain the lack of genetic differentiation. Accordingly, different selection on plumage colour in the two populations is either sufficiently strong so that gene flow has little impact on the pattern of colour variation, or differentiation of plumage colour occurred so recently that the (presumably) neutral, fast evolving markers employed here are unable to reflect the differentiation. Genetically, the Spanish population was significantly differentiated from the other populations, but the divergence was much more pronounced at mtDNA compared to microsatellites. This may reflect increased rate of differentiation by genetic drift at the mitochondrial, compared with the nuclear genome, caused by the smaller effective population size of the former genome. In accordance with this interpretation, a genetic pattern consistent with effects of small population size in the Spanish population (genetic drift and inbreeding) were also apparent at the microsatellites, namely reduced allelic diversity and heterozygous deficiency.     

Genetic and phenotypic variation in a colourful treefrog across five geographic barriers

Aim Understanding the patterns and processes underlying phenotype in a polytypic species provides key insights into microevolutionary mechanisms of diversification. The red‐eyed treefrog, Agalychnis callidryas, exhibits strong regional differentiation in colour pattern, corresponding to five admixed mitochondrial DNA clades. We evaluated spatial diversity patterns across multiple, putative barriers to examine the fine‐scale processes that mediate phenotypic divergence between some regions while maintaining homogeneity between others. Location We examined patterns of phenotypic diversification among 17 sites that span five putative biogeographic barriers in lower Central America (Costa Rica and Panama). Methods We tested the extent to which genetic distance (F_ST) derived from six multilocus nuclear genotypes covaried with measures of phenotypic distance (leg coloration) within and between biogeographic regions. We used linear regression analyses to determine the role of geographic and genetic factors in structuring spatial patterns of phenotypic diversity. Results The factors that best explained patterns of phenotypic diversity varied among biogeographic regions. We identified one geographic barrier that impeded gene exchange and resulted in concordant phenotypic divergence across the Continental Divide, isolating Caribbean and Pacific populations. Across Caribbean Costa Rican populations, one barrier structured phenotypic but not genetic diversity patterns, indicating a role for selection. In other regions, the putative barriers had no determining effect on either genetic or leg colour structure. Main conclusions The processes mediating the distribution and diversification of colour pattern in this polytypic, wide‐ranging treefrog varied among biogeographic regions. Spatially varying selection combined with the isolating effects of geographic factors probably resulted in the patchy distribution of colour diversity across Costa Rican and Panamanian populations.     

Landscape Ecotoxicology and Assessment of Risk at Multiple Scales

Traditional approaches to ecotoxicology and ecological risk assessment frequently have ignored the complexities arising due to the spatial heterogeneity of natural systems. In recent years, however, ecologists have become increasingly aware of the influence of spatial organization on ecological processes. Landscape ecology provides a conceptual and theoretical framework for the analysis of spatial patterns, the characterization of spatial aspects of ecosystem function, and the understanding of landscape dynamics. Incorporating the insights of landscape ecology into ecotoxicology will enhance our ability to understand and ultimately predict the effects of toxic substances in ecological systems. Ecological risk assessments need to explicitly consider multiple spatial scales, accounting for heterogeneity within contaminated areas and for the larger landscape context. A simple simulation model is presented to illustrate the effects of spatial heterogeneity by linking an individual-based toxicokinetic model with a spatially distributed metapopulation model. Dispersal of organisms between contaminated and uncontaminated patches creates a situation where risk analysis must consider a spatial extent broader than the toxicant-contaminated area. In general, the addition of a toxicant to a source patch (i.e., a net exporter of individuals) will have a greater impact than the same toxicant addition to a sink patch (i.e., a net importer of individuals).     

Genetic Diversity and the Survival of Populations

Abstract: In this comprehensive review, a range of factors is considered that may influence the significance of genetic diversity for the survival of a population. Genetic variation is essential for the adaptability of a population in which quantitatively inherited, fitness-related traits are crucial. Therefore, the relationship between genetic diversity and fitness should be studied in order to make predictions on the importance of genetic diversity for a specific population. The level of genetic diversity found in a population highly depends on the mating system, the evolutionary history of a species and the population history (the latter is usually unknown), and on the level of environmental heterogeneity. An accurate estimation of fitness remains complex, despite the availability of a range of direct and indirect fitness parameters. There is no general relationship between genetic diversity and various fitness components. However, if a lower level of heterozygosity represents an increased level of inbreeding, a reduction in fitness can be expected. Molecular markers can be used to study adaptability or fitness, provided that they represent a quantitative trait locus (QTL) or are themselves functional genes involved in these processes. Next to a genetic response of a population to environmental change, phenotypic plasticity in a genotype can affect fitness. The relative importance of plasticity to genetic diversity depends on the species and population under study and on the environmental conditions. The possibilities for application of current knowledge on genetic diversity and population survival for the management of natural populations are discussed.     

The accretion model of Neandertal evolution

The Accretion model of Neandertal evolution specifies that this group of Late Pleistocene hominids evolved in partial or complete genetic isolation from the rest of humanity through the gradual accumulation of distinctive morphological traits in European populations. As they became more common, these traits also became less variable, according to those workers who developed the model. Its supporters propose that genetic drift caused this evolution, resulting from an initial small European population size and either complete isolation or drastic reduction in gene flow between this deme and contemporary human populations elsewhere. Here, we test an evolutionary model of gene flow between regions against fossil data from the European population of the Middle and Late Pleistocene. The results of the analysis clearly show that the European population was not significantly divergent from its contemporaries, even in a subset of traits chosen to show the maximum differences between Europeans and other populations. The pattern of changes, over time within Europe of the traits in this subset, does not support the Accretion model, either because the characters did not change in the manner specified by the model or because the characters did not change at all. From these data, we can conclude that special phenomena such as near-complete isolation of the European population during the Pleistocene are not required to explain the pattern of evolution in this region.     

Patterns of genetic variability in Brazilian Littorinids (Mollusca): a macrogeographic approach

Macrogeographic studies are important for understanding gene flow patterns, and comparative data for related species with distinct bionomical traits may help to clarify the importance of such traits in natural populations. The aims of this study were to quantify the genetic variability and the populational structuring of three Brazilian littorinid species (Nodilittorina lineolata, Littoraria flava and L. angulifera) and to discuss the relationship between them, as well as each species’ mode of development and spatial distribution. We also investigated the species diversity in the ziczac complex. Isozyme analyses were done on 20 samples of N. lineolata, nine of L. flava and 10 of L. angulifera, collected along 4000 km of the Brazilian coast. Sixteen polymorphic loci were analysed in N. lineolata, 15 in L. angulifera and 17 in L. flava. All species showed high genetic variability. At sites where more than one species was present, there was a correlation among the values of gene diversity.The degree of interpopulational differentiation (N. lineolata, F_ST = 0.028; L. flava, F_ST = 0.054; L. angulifera, F_ST = 0.185) was coherent with the mode of larval development of each species. No linkage disequilibrium was found in N. lineolata. These findings, together with morphological evidence, corroborated the existence of only one species of the ziczac complex along the Brazilian coast.     

利用SSR标记分析玉米轮回选择群体的遗传多样性

利用SSR标记技术分析了玉米基础群体DC0及其选择两轮后的群体HSC2和MSC2以及基础群体XFC0和其选择一轮后的群体XFC1的遗传多样性。结果表明：49对引物在5个玉米群体中共扩增出185个等位位点,每个SSR座位的等位基因数目为1～7个,平均为3．8个;基础群体多态性位点总数和多态性位点比例比其改良群体的略高;DC0、HSC2和MSC2 3个群体的基因平均杂合度相似,XFC0与XFC1的基因平均杂合度相似;基础群体与改良群体的平均遗传距离也相似;累加各引物扩增的基因型种类,改良群体的基因型种类偏少,但这些差异均不显著。以上结果说明轮回选择的基础群体与其改良后群体的遗传变异相似,轮回选择可以保持群体的遗传变异范围,改变群体的遗传组成,增加群体内个体间的异质性。     

Genetic drift and gene flow in a prehistoric population of the Azapa valley and coast,Chile

The present paper studies the evolutionary process operating on prehistoric groups from the Azapa valley and coast (northern Chile). The sample consists of 237 crania from the Archaic Late, Early Intermediate, Middle, Late Intermediate, and Late periods. Six metric variables were used, which were transformed to eliminate the special environmental component and to increase the proportion of genetic variance. Population structure was assessed using a method based on quantitative genetic theory, which predicts a lineal relationship between average within-group phenotypic variance and group distance to the population centroid. Results indicate that 17.5% of the total variance accounts for special environmental variance. An excess in extraregional genetic flow is observed in the population corresponding to the Early Intermediate period in the valley. A reduced differentiation is observed between Archaic and Early Intermediate coastal groups, as well as between the latter and the inhabitants of the valley in the same period. Genetic differences between both areas increased substantially since the Middle period. Evidence indicates that long-range gene flow was lower on the coast than in the valley, the lowest estimated Fst being 0.0199 for the total population (coast and valley), 0.0111 for the coastal population, and 0.0057 for the valley. Results are discussed in terms of regional archeological and ethnohistorical evidence, and a microevolutionary model is presented to account for the biological history of the population.