Quantitative analysis of correlations among flower traits in Gerbera hybrida, Compositae. III. Genetic variability and structure of principal component traits

 A sample of 36 flower traits consisting of six morphological categories in the Davis population of gerbera was restructured into phenotypic and genetic principal component traits. The first 5 phenotypic principal component traits accounted for 62% of the total phenotypic variance of the 36 traits and have moderate to high heritablities. The first 5 genetic principal component traits account for 97% of total genetic variance and all have high heritability. Morphological structure of these component traits suggest an underlying process identified by the first genetic principal component involving largely trans and disk floret traits. The results of this study indicate that the quantitative genetic structure of the gerbera flower is controlled by a few independent components and that principal component analysis is a useful tool to reveal variation in this structure. These composite traits are heritable and are expected to respond to selection. Received: 20 September 1997 / Accepted: 19 January 1998     

蒙古冰草表型数量性状的变异与生境间的相关性

采用多因变量线性模型方差、变异系数、主成分分析及UPGMA聚类分析的数量统计方法,对来自内蒙古中东部地区的6个天然居群和2个栽培品种(品系)的花序10个数量性状进行了分析。结果表明,蒙古冰草在花序各部的表型性状上存在有居群内及居群间的差异,同时,天然居群的变异程度大于栽培品种,而且居群间的分化与生态环境因子有着密切的相关。     

High-level phenotypic variations in populations of Armeniaca sibirica in Nei Mongol,China

Aims Our objectives were to determine the variations in phenotypic traits of Armeniaca sibirica populations and their spatial patterns. Methods We used nested variation, coefficient of variation, multi-comparison, correlation analysis and principal component analysis to analyze the 23 phenotypic traits for 130 individuals in 13 populations of A. sibirica. Important findings The results showed that there were significant differences in phenotypic variations among and within populations. The variation was greater among populations (47.15%) than within population (16.43%). The mean phenotypic differentiation coefficient was 73.03% among populations, indicating the variance among populations being the main source of the phenotypic variation. The average variation coefficient of 23 traits ranged from 7.01% to 27.23%, with an average of 14.28%. The variation coefficient of nutlet was highest (15.67%), and the variation coefficient of fruit was smallest (12.11%). The phenotypic diversity is highest in Wanjiagou Tumotezuoqi and smallest in Horqin, Right Front Banner Chaersen. Longitude, mean annual precipitation and sunshine duration were significantly correlated with major traits of phenotypic. The 13 populations could be divided into four groups according to the principal component analysis. Leaf traits of Wula Mountain and nutlet traits of Archorchin Banner were significantly correlated with ecological and geographic factors.     

内蒙古山杏种群表型变异

为明确内蒙古山杏(Armeniaca sibirica)种群间和种群内的表型变异程度和变异规律, 以内蒙古山杏自然分布区的13个种群的23个表型性状为研究对象, 采用巢式方差分析、多重比较、变异分析、相关性分析和主成分分析等多种分析方法, 对种群间和种群内的表型多样性及其与地理生态因子的相关性进行了讨论。研究结果表明: 内蒙古山杏的表型性状在种群间和种群内均存在丰富的变异, 种群间的变异大于种群内的变异, 表型性状的平均分化系数为73.03%, 种群间变异是山杏表型变异的主要变异来源。各性状的平均变异系数为14.28%, 变异幅度为7.01%-27.23%, 其中核的变异系数最大, 果的变异系数最小。土默特左旗万家沟种群表型多样性最丰富, 科尔沁右翼前旗察尔森种群表型多样性最小。表型性状主要受经度、年降水量以及年日照时间3个主要地理生态因子影响。通过主成分分析可以把13个种源区划为四大类, 其中乌拉山种群的叶性状和阿鲁科尔沁旗种群的核性状受地理生态因子影响最大。     

Testing the grain-size model for the evolution of phenotypic plasticity

Phenotypic plasticity is the ability of a genotype to modify its phenotypic characteristics in response to different environments. Theory predicts that adaptive plasticity should primarily evolve in organisms that experience heterogeneous environments. An organism's dispersal rate is a key component in these models, because the degree of dispersal partly determines the extent of environmental heterogeneity. Here, I provide the first large-scale test of the theoretical prediction that phenotypic plasticity evolves in association with dispersal rate using meta-analysis of data from 258 experiments from the literature on plasticity in marine invertebrates. In line with predictions, phenotypic plasticity is generally greater in species with higher dispersal rates, suggesting that dispersal and environmental heterogeneity are important selective agents for evolution of plasticity in marine habitats.     

Ubiquinone systems of Coccidioides immitis, the causative agent of coccidioidomycosis

Abstract The ubiquinone (coenzyme Q) systems of eleven strains of Coccidioides immitis were determined by high performance liquid chromatography (HPLC). The ubiquinone profile of the fungi was shown to be homogeneous: in all of the strains, ubiquinone-10 (Q-10) was demonstrated to be the major component, with Q-9 as a minor component. The results imply that the ubiquinone system may serve as an additional phenotypic criterion for identifying the fungus.     

THE MEASUREMENT OF SELECTION ON QUANTITATIVE TRAITS: BIASES DUE TO ENVIRONMENTAL COVARIANCES BETWEEN TRAITS AND FITNESS

The use of regression techniques for estimating the direction and magnitude of selection from measurements on phenotypes has become widespread in field studies. A potential problem with these techniques is that environmental correlations between fitness and the traits examined may produce biased estimates of selection gradients. This report demonstrates that the phenotypic covariance between fitness and a trait, used as an estimate of the selection differential in estimating selection gradients, has two components: a component induced by selection itself and a component due to the effect of environmental factors on fitness. The second component is shown to be responsible for biases in estimates of selection gradients. The use of regressions involving genotypic and breeding values instead of phenotypic values can yield estimates of selection gradients that are not biased by environmental covariances. Statistical methods for estimating the coefficients of such regressions, and for testing for biases in regressions involving phenotypic values, are described.     

High-level phenotypic variations in populations of Armeniaca sibirica in Nei Mongol,China北大核心CSCD

Aims: Our objectives were to determine the variations in phenotypic traits of Armeniaca sibirica populations and their spatial patterns. Methods: We used nested variation, coefficient of variation, multi-comparison, correlation analysis and principal component analysis to analyze the 23 phenotypic traits for 130 individuals in 13 populations of A. sibirica. Important findings: The results showed that there were significant differences in phenotypic variations among and within populations. The variation was greater among populations (47.15%) than within population (16.43%). The mean phenotypic differentiation coefficient was 73.03% among populations, indicating the variance among populations being the main source of the phenotypic variation. The average variation coefficient of 23 traits ranged from 7.01% to 27.23%, with an average of 14.28%. The variation coefficient of nutlet was highest (15.67%), and the variation coefficient of fruit was smallest (12.11%). The phenotypic diversity is highest in Wanjiagou Tumotezuoqi and smallest in Horqin, Right Front Banner Chaersen. Longitude, mean annual precipitation and sunshine duration were significantly correlated with major traits of phenotypic. The 13 populations could be divided into four groups according to the principal component analysis. Leaf traits of Wula Mountain and nutlet traits of Archorchin Banner were significantly correlated with ecological and geographic factors.     

云南引种印楝实生种群的表型变异

为了揭示印楝(Azadirachta indica)实生种群表型变异程度和变异规律, 以云南引种印楝人工林为研究对象, 基于9个种群90个单株14个表型性状严格细致的测量, 采用单因素方差分析、巢式方差分析、相关分析、协方差主成分分析(S法)和非加权配对算术平均法(UPGMA)聚类分析等数理方法, 分析了种群的表型变异。结果表明: 印楝种内表型性状在种群间和种群内均存在着较丰富的差异, 种群内的变异大于种群间的变异, 种群间的分化相对较小。对表型性状进行的变异系数多重比较和协方差主成分分析(S法)均显示, 结实和种子化学成分相关性状的变异是造成印楝表型变异的主要来源。利用种群间欧氏距离进行的UPGMA聚类分析结果进一步表明, 印楝9个种群可以分为4类, 表型性状并没有严格依地理距离而聚类。研究结果为印楝的遗传改良工作奠定了基础, 为制定育种策略和人工经营对策提供了科学依据。     

濒危植物水青树叶表型性状多样性分析

通过对水青树(Tetracentron sinense)24个居群161株个体的10个叶形态性状与7个叶表皮微形态性状进行观测,采用描述性统计、相关性分析、主成分分析以及聚类分析对其叶表型性状多样性进行研究。结果表明,水青树叶表型性状变异系数的变化幅度为4.21%～49.23%,Shannon-wiener多样性指数在0.82～2.07之间,其中叶最长(LLEST)性状最高,叶先尖削(LBPI)性状最低,平均1.80;叶形态性状相关性分析表明,性状之间存在密切联系,有47对性状呈极显著正相关,15对性状呈极显著负相关;主成分分析中前三个主成分的贡献率可达83.712%,可靠地代表了水青树表型性状的分布;Q型聚类分析发现,当阈值为15时,24个水青树居群可分为3类。水青树总体表现出较低表型多样性,唐家河、虹口、佛坪三个居群应作为保护与管理的重点群体。     

不同产地降香黄檀种子和幼苗性状的变异研究

为了探讨不同产地降香黄檀(Dalbergia odorifera)种子和幼苗的表型性状变异规律,该研究以来源于海南、福建、广西、广东等省/区10个产地降香黄檀的种子及在广西桂林培育的幼苗为材料,采用方差分析、相关性分析和主成分分析对其种子和幼苗生长的9个表型性状进行了比较研究。结果表明:降香黄檀种子和幼苗的表型性状存在较大变异,9个性状间均差异极显著,各性状平均变异系数(CV)为12.50%,变异系数范围在7.94%～18.89%,幼苗生长性状的变异高于种子性状的变异,说明种子性状的稳定性较高。相关分析表明各表型性状间及表型性状与地理-气候因子间均存在不同的相关性,各表型性状与经度、纬度及年降水量均无显著相关性,而海拔、年均温度与年降雨量是影响降香黄檀种子和幼苗性状的主要因子。利用主成分综合得分法,筛选出了3个在种子形态、幼苗生长和萌发情况等方面较好的家系,按综合得分排序分别为仙游产地、儋州产地、尖峰岭产地。研究结果可为降香黄檀优良种质资源的筛选提供科学依据。     

刺萼龙葵种群在中国不同分布地区的表型变异

外来有害植物刺萼龙葵(Solanum rostratum)又名黄花刺茄, 已扩散至中国多省, 各地的种群在表型上存在差异。为揭示刺萼龙葵在中国不同分布区表型变异产生的原因及变异规律, 该文以来自中国9个地区的刺萼龙葵种群的种子为材料, 进行同质生物园种植。通过对营养和生殖器官共10个表型性状进行严格细致的测量, 并采用单因素方差分析(one-way ANOVA)、变异系数分析、主成分分析、聚类分析(UPGMA)和相关性分析等数理方法, 分析了各个种群的表型变异。结果表明: (1)来自不同种群的刺萼龙葵在10个性状上差异均极显著(p < 0.01), 表明种群间的性状差异具有遗传上的稳定性; (2)营养性状平均变异系数(CV = 18.2%)显著高于花部性状(CV = 9%), 结合主成分分析的结果, 可得出冠幅、 花冠直径、节间距以及株高是决定表型变异的主要代表性状; (3)种群间的聚类分析将刺萼龙葵的9个种群划分为3类, 表型性状并没有依地理距离而聚类; (4)地理因子中, 对性状影响最大的是海拔, 其次是经度, 最后是纬度。     

Seed predators exert selection on the subindividual variation of seed size

Subindividual variation among repeated organs in plants constitutes an overlooked level of variation in phenotypic selection studies, despite being a major component of phenotypic variation. Animals that interact with plants could be selective agents on subindividual variation. This study examines selective pressures exerted during post‐dispersal seed predation and germination on the subindividual variation of seed size in hawthorn (Crataegus monogyna). With a seed offering experiment and a germination test, we estimated phenotypic selection differentials for average and subindividual variation of seed size due to seed predation and germination. Seed size affects germination, growth rate and the probability of an individual seed of escaping predation. Longer seeds showed higher germination rates, but this did not result in significant selection on phenotypes of the maternal trees. On the other hand, seed predators avoided wider seeds, and by doing so exerted phenotypic selection on adult average and subindividual variation of seed size. The detected selection on subindividual variation suggests that the levels of phenotypic variation within individual plants may be, at least partly, the adaptive consequence of animal‐mediated selection.     

新疆阿勒泰地区5个大赖草种群的表型多样性分析

为了解大赖草种群﹝Leymus racemosus ( Lam.) Tzvel.﹞的表型变异规律及多样性特征,对分布于新疆阿勒泰地区的5个大赖草种群(分别位于阿勒泰市、福海县、布尔津县和哈巴河县)的16个表型性状进行了测定;在此基础上,对各表型性状进行了Shannon-Weaver指数( H＇)分析和主成分分析。结果表明：各种群间的16个表型性状均存在较大差异,其中分布于哈巴河县的2个种群各表型性状的平均值均较高。种群内各表型性状的变异系数为5.97%~40.05%,差异较大;其中,穗下第一节间长度的变异系数在各种群内均较大(17.16%~40.05%);总体上看,种群内与营养生长有关的性状(如穗下第一节间长度、剑叶长度和宽度等)变异较大,而与繁殖有关的性状变异较小。在种群间,穗下第一节间长度、剑叶长度和宽度的变异系数均较大,分别为31.85%、26.87%和27.85%;而小穗和外颖长度以及穗节数的变异系数均较小,分别为15.21%、16.53%和16.91%。5个种群间16个表型性状的H＇值均有较大差异,并且,种群内各表型性状的H＇平均值(1.660)明显高于种群间(0.239)。主成分分析结果显示：前5个主成分的累计贡献率为80.210%,其中,第1主成分中与营养器官相关的性状(如株高、穗下第一节间长度、剑叶长度和宽度、茎节数)载荷较大,第2至第4主成分中与繁殖器官相关的性状(如穗长度和宽度、外颖和内颖长度、小穗长度和宽度以及外稃长度)载荷较大,表明这12个性状为大赖草种群表型性状变异的主要因子。研究结果显示：大赖草种群间的表型多样性低于种群内,且营养器官的表型变异是导致大赖草种群表型多样性的主要因子。     

Reciprocal selection at the phenotypic interface of coevolution

Coevolutionary interactions depend upon a phenotypic interfaceof traits in each species that mediate the outcome of interactionsamong individuals. These phenotypic interfaces usually involveperformance traits, such as locomotion or resistance to toxins,that comprise an integrated suite of physiological, morphologicaland behavioral traits. The reciprocal selection from speciesinteractions may act directly on performance, but it is ultimatelythe evolution of these underlying components that shape thepatterns of coevolutionary adaptation in performance. Bridgingthe macroevolutionary patterns of coevolution to the ecologicalprocesses that build them therefore requires a way to dissectthe phenotypic interface of coevolution and determine how specificcomponents of performance in one species exert selection oncomplimentary components of performance in a second species.We present an approach for analyzing the strength of selectionin a coevolutionary interaction where individuals interact atrandom, and for identifying which component traits of the phenotypicinterface are critical to mediating coevolution. The approachis illustrated with data from a predator-prey arms race betweengarter snakes and newts that operates through the interfaceof tetrodotoxin (TTX) and resistance to it.     

The effect of phenotypic variation on metapopulation persistence

Demographic stochasticity (due to the probabilistic nature of the birth–death process) and demographic heterogeneity (between-individual differences in demographic parameters) have long been seen as factors affecting extinction risk. While demographic stochasticity can be independent of underlying species traits, demographic heterogeneity may strongly depend on phenotypic variation. However, how phenotypic variation can affect extinction risk is largely unknown. Here, I develop a stochastic metapopulation model that takes into account the effects of demographic stochasticity and phenotypic variation in the traits controlling colonization rates to assess what the effect of phenotypic variation may be on the persistence of the metapopulation. Although phenotypic variation can lead to a decrease in metapopulation persistence under some conditions, it also may lead to an increase in persistence whenever phenotypic mismatch—or the distance between the optimal trait value and the population mean—is large. This mismatch can in turn arise from a variety of ecological and evolutionary reasons, including weak selection or a recent history of invasion. Last, the effect of phenotypic variation has a deterministic component on colonization rates, and a stochastic component on persistence through colonization rates, but both are important to understand the overall effect. These results have important implications for the conservation of threatened species and management practices that may historically have overlooked phenotypic variation as unimportant noise around mean values of interest.     

Genetic covariance structure of growth in the salamander Ambystoma macrodactylum

The size of an organism at any point during ontogeny often has fitness consequences through either direct selection on size or through selection on size-related morphological, performance, or life history traits. However, the evolutionary response to selection on size across ontogeny (a growth trajectory) may be limited by genetic correlations across ages. Here we characterize the phenotypic and genetic covariance structure of length and mass growth trajectories in a natural population of larval Ambystoma macrodactylum using function-valued quantitative genetic analyses and principal component decomposition. Most of the phenotypic and genetic variation in both growth trajectories appears to be confined to a single principal component describing a pattern of positive covariation among sizes across all ages. Higher order principal components with no significant associated genetic variation were identified for both trajectories, suggesting that evolution towards certain patterns of negative covariation between sizes across ages is constrained. The well-characterized positive relationship between size at metamorphosis and fitness in pond-breeding amphibians predicts that the across-age covariance structure will strongly limit evolution only if there is negative selection on size prior to metamorphosis. The pattern of genetic covariation observed in this study is similar to that observed in other vertebrate taxa, indicating that size may often be highly genetically and phenotypically integrated across ontogeny. Additionally, we find that phenotypic and genetic analyses of growth trajectories can yield qualitatively similar patterns of covariance structure.     

Epigenetics and phenotypic variation in mammals

What causes phenotypic variation? By now it is clear that phenotype is a result of the interaction between genotype and environment, in addition to variation not readily attributable to either. Epigenetic phenomena associated with phenotypic variation at the biochemical, cellular, tissue, and organism level are now well recognized and are likely to contribute to the “intangible variation” alluded to. While it is clear that epigenetic modifications are mitotically heritable, the fidelity of this process is not well understood. Inheritance through more than one generation of meioses is even less well studied. So it remains unclear to what extent epigenetic changes contribute to phenotypic variation in natural populations. How might such evidence be obtained? What are the features of phenotypes that might suggest an epigenetic component? How much of the epigenetic component is truly independent of genetic changes? The answers to such questions must come from studies designed specifically to detect subtle, stochastically determined phenotypic variation in suitable animal models.     

Identification and characterization of a locus which regulates multiple functions in Pseudomonas tolaasii, the cause of brown blotch disease of Agaricus bisporus.

Pseudomonas tolaasii, the causal agent of brown blotch disease of Agaricus bisporus, spontaneously gives rise to morphologically distinct stable sectors, referred to as the phenotypic variant form, at the margins of the wild-type colonies. The phenotypic variant form is nonpathogenic and differs from the wild type in a range of biochemical and physiological characteristics. A genomic cosmid clone (pSISG29) from a wild-type P. tolaasii library was shown to be capable of restoring a range of characteristics of the phenotypic variant to those of the wild-type form, when present in trans. Subcloning and saturation mutagenesis analysis with Tn5lacZ localized a 3.0-kb region from pSISG29, designated the pheN locus, required for complementation of the phenotypic variant to the wild-type form. Marker exchange of the Tn5lacZ-mutagenized copy of the pheN locus into the wild-type strain demonstrated that a functional copy of the pheN gene is required to maintain the wild-type pathogenic phenotype and that loss of the pheN gene or its function results in conversion of the wild-type form to the phenotypic variant form. The pheN locus contained a 2,727-bp open reading frame encoding an 83-kDa protein. The predicted amino acid sequence of the PheN protein showed homology to the sensor and regulator domains of the conserved family of two component bacterial sensor regulator proteins. Southern hybridization analysis of pheN genes from the wild type and the phenotypic variant form revealed that DNA rearrangement occurs within the pheN locus during phenotypic variation. Analysis of pheN expression with a pheN::lacZ fusion demonstrated that expression is regulated by environmental factors. These results are related to a model for control for phenotypic variation in P. tolaasii.