Environmentally induced morphological variation in the Barnacle Goose,Branta leucopsis

The environmental conditions to which juvenile barnacle geese (Branta leucopsis) were exposed during growth were found to affect their body size at fledging as well as their final adult body size. Small juveniles showed compensatory growth from the time of fledging up to one year of age, but this did not fully compensate the differences in body size that were established before fledging. The variation in protein content in plants eaten during growth could probably explain the observed body size differences, sometimes of more than 10%, between different categories of adult geese. Our results imply that one cannot infer selection on morphological characters from differences between samples of adult birds from different localities or from different cohorts within a population, without first showing that environmental conditions during growth do not affect the development of the characters under study.     

Phenotypic plasticity inPotamogeton (Potamogetonaceae)

Sources of the extensive morphological variation of the species and hybrids ofPotamogeton were studied, especially from the viewpoint of the stability of the morphological characters used inPotamogeton taxonomy. Transplant experiments, the cultivation of clones under different values of environmental factors, and the cultivation of different clones under uniform conditions were performed to assess the proportion of phenotypic plasticity in the total morphological variation. Samples from 184 populations of 41Potamogeton taxa were grown. The immense range of phenotypic plasticity, which is possible for a single clone, is documented in detail in 14 well-described examples. The differences among distinct populations of a single species observed in the field were mostly not maintained when grown together under the same environmental conditions. Clonal material cultivated under different values of environmental factors produced distinct phenotypes, and in a few cases a single genotype was able to demonstrate almost the entire range of morphological variation in an observed trait known for that species. Several characters by recent literature claimed to be suitable for distinguishing varieties or even species were proven to be dependent on environmental conditions and to be highly unreliable markers for the delimiation of taxa. The unsatisfactory taxonomy that results when such classification of phenotypes is adopted is illustrated by three examples from recent literature. Phenotypic plasticity was found to be the main source of morphological variation within the species ofPotamogeton, having much more influence than morphological differences caused by different genotypes.     

MORPHOLOGICAL VARIATION AND DEVELOPMENT IN RAMALINA MENZIESII TAYL.

The common west coast lichen Ramalina menziesii Tayl. has been studied in an attempt to determine the extent of morphological variation and to understand the factors that determine its form. An analysis of a typical population near Santa Barbara, CA, suggested that intrapopulation variation in form was controlled primarily by size increase during growth. Test populations obtained from latitudes as far north as 54°N and as far south as 28°N had values for various morphological characters that were very similar to the Santa Barbara population. It is concluded that variation in form may be the result of differential rates of growth and possibly varying frequency of environmental stresses which disintegrate the thallus.     

Geographical variation in heading traits in wild emmer wheat, Triticum dicoccoides. I. Variation in vernalization response and ecological differentiation

 Geographical variation in vernalization response and narrow-sense earliness was investigated for accessions of wild emmer wheat, Triticum dicoccoides, collected in Israel. Wide variation between and within populations was observed in both characters. The analysis of vernalization response showed that 2 accessions from Tabigha were of a strong spring growth habit, and thus wild emmer wheat was classified into four types, i.e., strongly spring type, moderately spring type, moderately winter type, and strongly winter type, according to their vernalization response. Whereas winter types were frequently found in most populations except that of Tabigha, the distribution of spring types was sporadic and restricted to warmer areas. It was thus suggested that spring type in T. dicoccoides might have evolved from a winter prototype as an adaptation to warmer conditions. Within moderately winter and moderately spring types, quantitative differences in vernalization response, measured as Dof₇₀/Dof₂₀ and Dof₂₀/Dof₀, were observed between populations. Inter- and intra-population variation in vernalization response could be explained to some extent by the difference in growing conditions at each habitat. It was clearly indicated that environmental heterogeneity caused ecogenetic differentiation in wild emmer wheat in Israel. Wild emmer wheat also varied considerably for narrow-sense earliness, ranging from 32.9 days to 69.5 days among accessions. However, it was difficult to explain its geographical variation simply by a linear relationship with environmental factors, and a nonlinear relationship and/or unknown microgeographic heterogeneity may be responsible. Received: 18 March 1996/Accepted: 13 December 1996     

Enzyme heterozygosity,metabolism, and developmental stability

Developmental homeostasis, measured as either fluctuating asymmetry or variance of morphological characters, increases with enzyme heterozygosity in many, but not all, natural populations. These results have been reported forDrosophila, monarch butterflies, honeybees, blue mussels, side-blotched lizards, killifish, salmonid fishes, guppies, Sonoran topminnows, herring, rufous-collared sparrows, house sparrows, brown hares, white-tailed deer, and humans. Because heterozygosity at a few loci can not predict heterozygosity of the entiry genome, these loci must be detecting localized zones that influence the developmental environment. Studies of malate dehydrogenase in honeybees,Apis mellifera, and lactate dehydrogenase in killifish,Fundulus heteroclitus, revealed that developmental homeostasis varied with heterozygosity of individual loci. Heterozygotes differed from homozygotes in fluctuating asymmetry, morphological variance, and in correlations between morphological characters. The protein loci in these studies code for enzymes, and therefore do not directly influence morphological characters. However, some enzymatic loci substantially influence metabolism, and contribute to variation in the amount of energy available for development and growth. This argument can be made most convincingly for the LDH polymorphism in killifish. LDH genotypes differ in enzyme kinetic properties that measure differences in physiological efficiency, and these differences produce measurable and predictable differences in physiology and development. Under environmental conditions which impose a stress upon development, genotypes at these loci may have different amounts of energy available for development, and consequently exhibit different levels of developmental homeostasis.     

濒危植物马蹄参枝叶形态变异与环境因子的相关性分析

调查马蹄参在湖南、广东、广西、云南4省9个天然种群20项枝叶的形态指标在种群内和种群间的表型变异,运用相关分析揭示枝和叶形态指标间以及与环境因子之间的相关性,并进行聚类分析(UPGMA)和主成分分析.结果表明:各性状在种群内和种群间均存在一定变异性.广西花坪自然保护区两个种群(HP1,HP2)枝叶形态性状(尤其是枝)的...     

CONTRASTING PATTERNS OF HERITABLE GEOGRAPHIC VARIATION IN SHELL MORPHOLOGY AND GROWTH POTENTIAL IN THE MARINE GASTROPOD BEMBICIUM VITTATUM: EVIDENCE FROM FIELD EXPERIMENTS

Similar phenotypes do not always imply similar genotypes. In species distributed over a broad latitudinal range, geographical variation in morphological and life-history traits may reflect very different relations between genotypic and environmental effects on these traits. Patterns of selection among latitudinally separated sites may minimize phenotypic differences in life-history traits but promote phenotypic differences in form. Thus, for example, latitudinal variation in temperature often leads to genetically based metabolic differences that minimize differences in growth rate among populations at different latitudes (countergradient variation). However, variation in habitat experienced by the same populations may promote genetically based differences in shell form (cogradient variation). Few attempts have been made to assess simultaneously such mosaic effects of natural selection on the genetic basis of variation in both morphological and life-history traits among geographically separated populations. I quantified the extent to which widely separated populations of the rocky shore marine gastropod Bembicium vittatum exhibited genetic differences in shell shape, shell pattern, and growth rate. Bembicium vittatum occurs naturally at only three widely separated locations on the Western Australian coast. Individuals were transplanted from all three locations to a latitudinally intermediate site, where they were released in different pairwise combinations and allowed to reproduce. F₁ offspring from crosses between same- or different-source parents were identified using allozyme markers. When grown in a common environment, offspring from same-source parents exhibited similar differences in shell shape and pattern, but dramatic differences in growth rates, compared to native populations. Genetic variation therefore exists for all three traits. Growth rates in the common environment were positively correlated with latitude of the source population, confirming the existence of countergradient variation for growth associated with metabolic compensation. In addition, for both shell shape and growth rate, hybrids exhibited phenotypes roughly midway between the same-source parents, suggesting that genetic differences have a large additive component. In contrast, when one parent had pigmented spots, the offspring also had spots, suggesting a strong dominance component to the genetic basis of shell pattern. Genetic differences therefore yield different morphological phenotypes but similar life-history phenotypes, among latitudinally distant populations, and confirm a pattern of mosaic evolution in B. vittatum.     

Morphological variability between wild populations and inbred stocks of a Chinese minnow, Gobiocypris rarus

Gobiocypris rarus, a small, native cyprinid fish, is currently widely used in research on fish pathology, genetics, toxicology, embryology, and physiology in China. To develop this species as a model laboratory animal, inbred strains have been successfully created. In this study, to explore a method to discriminate inbred strains and evaluate inbreeding effects, morphological variation among three wild populations and three inbred stocks of G. rarus was investigated by the multivariate analysis of eight meristic and 30 morphometric characters. Tiny intraspecific variations in meristic characters were found, but these were not effective for population distinction. Stepwise discriminant analysis and cluster analysis of conventional measures and truss network data showed considerable divergence among populations, especially between wild populations and inbred stocks. The average discriminant accuracy for all populations was 82.1% based on conventional measures and 86.4% based on truss data, whereas the discriminant accuracy for inbred strains was much higher. These results suggested that multivariate analyses of morphometric characters are an effective method for discriminating inbred strains of G. rarus. Morphological differences between wild populations and inbred strains appear to result from both genetic differences and environmental factors. Thirteen characters, extracted from stepwise discriminant analysis, played important roles in morphological differentiation. These characters were mainly measures related to body depth and head size.     

Inter- and intra-population morphological differences between wild and farmed Atlantic salmon juveniles

Whether population-specific morphological differences were detectable in small (26–52 mm) Atlantic salmon Salmo salar parr reared under similar conditions was tested. Discrimination based on morphological characters was total (100%) between the fish of farmed origin (from AquaGen) and four wild fish populations. Between the four wild populations the corresponding discrimination was 59·8–86·3%. The inter-population variation in morphological characters was larger than the intra-population variation. The fish originating from the local populations at Driva and Innfjord were narrower in body form, whereas fish from the AquaGen and Innfjord populations had smaller and less pointed heads with smaller eyes. The Driva population fish had the smallest mouth while the longest pectoral fin was found in the Bjoreio population, the river that also has the largest fall gradient. Population-specific morphological characters were thus detectable among Atlantic salmon parr relatively rapidly after yolk absorption.     

浙江省野生蜡梅花部形态变异及其与环境因子的相关性

以浙江省蜡梅自然分布区的5个居群为研究对象,采用巢式方差分析、主成分分析、相关分析、聚类分析等多种分析方法,探究蜡梅花部的形态变异及其与环境因子相关性以及居群间和居群内的表型多样性。结果表明:蜡梅花部性状中除雄蕊长度、雌蕊数、雌蕊长度、内被片数以外,其他12个性状在居群间均有极显著差异。胚珠数的平均变异系数最大,花冠内径的平均变异系数最小,各性状的平均变异系数为15.03%(10.81%—23.38%)。五尖山的表型多样性最丰富,碧东山居群最小,种群间平均表型分化系数为44.38%(1.57%—89.62%),种群内变异大于种群间变异,种群内变异是花部变异的主要来源。主成分分析显示花冠直径、花冠内径、花筒深度和中被片长对种群变异起主要贡献作用。花部多数性状间存在显著或极显著的相关关系,生态因子中花部性状与土壤酸度相关性最大,土壤中花部性状与大量元素相关性最大,微量元素次之,中量元素最小。通过UPGMA聚类分析可以将5个种群分成两组。浙江省野生蜡梅花部形态存在丰富的变异和多样性,花部部分性状与土壤中钙、铁、铜含量和海拔有显著或极显著相关关系。     

Hybridization and genetic variation in Danish populations of European crab apple (Malus sylvestris)

The aim of the present study was to investigate the genetic variation in Danish populations of the endangered European crab apple (Malus sylvestris). Special emphasis was given to hybridization between the wild species and its cultivated relative Malus ×domestica. A total of 178 wild individuals from four Danish populations were studied along with a reference sample of 29 old cultivars. The genetic variation within and among samples was studied at ten microsatellite marker loci. Additionally, a morphological analysis was carried out to identify hybrids and test for correspondence between phenotypic and genotypic indices of hybridization. From application of ordination and a model-based cluster analysis to the molecular data, two clusters were identified consisting of wild and cultivated individuals, respectively. This indicates that pronounced admixture between the two species is not present. At the population level, a high correspondence was found between geographic isolation from M. ×domestica and genotypic and morphological indices of hybridization. As expected, isolated populations appeared less affected by hybridization than poorly isolated populations. Isolated “pure” M. sylvestris populations could thus be identified. However, morphological and molecular evidences of hybridization were found to be divergent at the individual level. This is suggestive of some historical introgression into the M. sylvestris gene pool and indicates that relying exclusively on either morphological or molecular characters as diagnostic markers in studies of hybridization between M. ×domestica and M. sylvestris might lead to fallible results. Combined application of genetic and morphological markers is therefore recommended.     

贵州省野生皂荚种实表型性状多样性分析

为深入了解贵州省野生皂荚(Gleditsia sinensis)荚果表型性状的遗传多样性及其变异类型,为皂荚的遗传改良、种质鉴定、亲本选择以及品种培育奠定理论基础。该研究以贵州省7个野生皂荚群体70个个体为研究对象,采用方差分析、主成分分析、相关性分析及多性状综合评价等方法对皂荚群体的10个种实表型性状进行系统分析和综合评价。结果显示：(1)所测皂荚的表型性状差异在群体内均达到极显著水平(P＜0.01);在群体间,除每荚粒数、种子宽、种子长宽积以及种子长宽比之外,其余表型性状的差异均达极显著水平(P＜0.01)。(2)7个居群野生皂荚各性状平均变异系数为21.16%,其中凯里市(P4)居群的变异系数最高(24.44%);居群间荚果的变异(29.22%)高于种子的变异(11.04%),且变异主要来自于群体内。(3)相关分析显示,皂荚种实各性状之间存在不同程度的关联性;主成分分析显示,前4个主成分(皂荚种子大小、单个荚果出籽数量、种子形态指数因子、与荚果长和种子厚相关的因子)的累积贡献率达69.783%,可基本反映皂荚表型性状的大部分信息;以10个种实性状对皂荚野生群体进行综合评价发现,来自于惠水县(P7)群体的皂荚种实性状综合评价最高。研究表明,贵州省野生皂荚在群体间及群体内具有丰富的表型变异,且群体内的变异大于群体间的变异,变异主要来自于群体内。     

Differences in morphological growth trajectories between greenside darter Etheostoma blennioides populations from two distinct drainages

The greenside darter Etheostoma blennioides is a small-bodied benthic stream fish that occurs in multiple drainages of the eastern USA. Previous studies have revealed some morphological differentiations among greensides from isolated drainage systems but growth relationships among functional morphological characteristics have not been examined within and between populations. Specifically, we tested for differences in functional morphology and allometric distinctions in morphological growth trajectories between greenside populations from two drainages, the Osage River and White River. Morphological differences between individuals of the two drainages included more dorso-ventrally compressed bodies, longer snouts and larger jaw features in White River darters. Furthermore, body depth, snout length and jaw width grow at significantly different trajectories in individuals of the two drainages. Individuals of the White River drainage (generally a higher gradient stream system) become comparatively more streamlined and develop proportionately larger feeding related traits during growth. These results suggest that individuals of both drainages share a similar morphology during early life but deviate during continued development and this may be partially due to environmentally induced plastic response. This study represents a novel approach for comparing morphological development among fish populations and presents environmental factors (e.g., stream gradient and elevation) that potentially influence functional characteristics.     

Phenotypic plasticity of Vaccinium meridionale (Ericaceae) in wild populations of mountain forests in Colombia

Vaccinium meridionale is a promising crop for the Andean region of South America and is currently available only in the wild. Spontaneous populations of this plant are found across the Colombian mountains, but very few published records on this plant morphology are available. A zonification study of V. meridionale was conducted in four principal areas of a low mountain forest of Colombia (Provinces of Boyacá, Cundinamarca, Santander and Nari?o) in 2007. A total of 20 populations and 100 plants of V. meridionale were individually characterized and surveyed, using a list of 26 characters of morphological variables (9 quantitative and 17 qualitative characters). Our results indicated that natural populations of V. meridionale might be found in the tropical forest under a highly heterogeneous climate and microclimate conditions, at different mountain regions between 2 357 and 3 168masl. The shrubs of V. meridionale exhibited a high level of intra-population variation in several quantitative (plant height, stem diameter) and qualitative (growth habit, ramification density, presence of anthocyanins in stems) morphological characters, suggesting an environmentally induced phenotypic plasticity. Plant height, stem diameter and foliar density were the most variable morphological traits, with coefficients of variation higher than 50%. However, several quantitative characters of its reproductive potential, such as berry dimensions, rachis length and number of flowers per inflorescence, resulted with low plasticity with coefficients of variation lower than 30.2%, indicating that these characters were genetically determined. The highest correlation coefficients (p < 0.05) resulted to be between fruit length and fruit width (0.90), leaf length and leaf width (0.78), plant height and stem diameter (0.60), and inflorescence length and flowers number per inflorescence (0.57). The results suggest that an important genetic resource exists for this species in the wild. Low variation in fruit size, which constitutes a target trait for plant breeders, could be useful for selection of cultivars of V. meridionale. The results of this study could also be applied in conservation programs aimed to protect these diverse populations in the mountain forests of Colombia.     

Environmentally controlled phenotypic plasticity of morphology and polypeptide expression in two populations of Daphnia pulex (Crustacea: cladocera)

Summary Two local Daphnia pulex populations which are subject to different types of seasonally varying predation pressures were studied. Individuals from both populations were raised in laboratory environments which simulated either summer or winter temperatures and photoperiods. When individuals from the same parthenogenetic clone were raised in different seasonal environments, each clone exhibited phenotypic variation specific to each of the seasonal environments. Intraclonal phenotypic plasticity was found in both populations at two different levels: variation in morphological characters, and variation in the expressed polypeptide phenotypes. Summer environmental conditions induced predator-resistant morphological traits, while winter conditions induced predator-susceptible ones. From 65% to 71% of over 200 major polypeptides were specifically expressed in either one seasonal environment or the other. This is evidence for the existence of environmentally induced switching between alternate developmental programs. Clones from the population with the least year to year predictability of seasonal predation pressure showed more interclonal variation in environment specific phenotypic expression than clones from the more predictably fluctuating environment.     

ENVIRONMENTAL AND GENETIC DETERMINANTS OF PLANT SIZE IN VIOLA SORORIA

Survivorship and fecundity in the forest herb, Viola sororia, are size-dependent. The basis of size variation among individuals of Viola sororia was investigated with a uniform environment experiment. Plants collected from natural populations were vegetatively reproduced and grown under two light regimes in a greenhouse. Analysis of quantitative variation showed: 1) significant differences between light treatments for characters related to plant shape and relative growth rate; 2) significant among-genet variation for plant size, plant shape and relative growth rate but none for physiological characters; and 3) a size threshold for cleistogamous seed production and rhizome production. Heritability estimates for the characters associated with plant size and shape ranged from 0.09 to 0.39, indicating significant genetic determination for these traits. In addition, among-genet differences in relative growth rate were substantial. The results of this study suggest that the size variation found in natural populations is not solely a function of environmental heterogeneity but is significantly influenced by the genotypes composing the population.     

Morphological variations of Caragana microphylla populations in the Xilingol steppe and their relationship with environmental factors

The morphological variations of branches, leaves, flowers, fruits and seeds of Caragana microphylla and their correlations with environmental factors were analyzed based on five natural populations in the Xilingol steppe, Inner Mongolia, China. Nested variation analysis showed that there were significant differences in all of the 28 morphological characters within and among populations in 16 morphological characters, and the variations within populations were much greater than those among populations in most morphological characters. Cluster analysis showed that the five populations of C. microphylla could be divided into two groups in morphological characters, and there was significant positive correlation between the divergence of morphological characters matrix and geographical distance matrix. Principal component analysis showed that leaflet length, area of a compound leaf, fresh-mass of a compound leaf, and shoot fresh-mass were main morphological characters that varied among C. microphylla populations. Spearman correlation analysis showed that there were significant correlations between some morphological characters and soil factors. Soil N:P ratio, available N content, total N content, organic matter content and soil water content were main factors that were associated with morphological characters of C. microphylla.     

Comparative floral and vegetative differentiation between two European Aquilegia taxa along a narrow contact zone

As a first step in determining the identity and relative importance of the evolutionary forces promoting the speciation process in two closely related European taxa of Aquilegia, we investigated the levels of morphological variation in floral and vegetative characters over the narrow region where their ranges enter into contact, and evaluate the relative importance of both types of traits in their differentiation. A total of 12 floral and ten vegetative characters were measured on 375 plants belonging to seven A. vulgaris populations and six A. pyrenaica subsp. cazorlensis populations located in southeastern Spain. Floral and vegetative morphological differentiation occur between taxa and among populations within taxa, but only vegetative characters (particularly plant height and leaf petiolule length) contribute significantly to the discrimination between taxa. Differentiation among populations within taxa is mostly explained by variation in floral traits. Consequently, morphological divergence between the two taxa cannot be interpreted as an extension of among-population differences occurring within taxa. Multivariate vegetative, but not floral, similarity between populations could be predicted from geographical distance. Moreover, the key role of certain vegetative traits in the differentiation of A. vulgaris and A. p. cazorlensis could possibly be attributable to the contrasting habitat requirements and stress tolerance strategies of the two taxa. These preliminary findings seem to disagree with the currently established view of the radiation process in the genus Aquilegia in North America, where the differentiation of floral traits seems to have played a more important role.     

Morphological variations of Caragana microphylla populations in the Xilingol steppe and their relationship with environmental factors

The morphological variations of branches, leaves, flowers, fruits and seeds of Caragana microphylla and their correlations with environmental factors were analyzed based on five natural populations in the Xilingol steppe, Inner Mongolia, China. Nested variation analysis showed that there were significant differences in all of the 28 morphological characters within and among populations in 16 morphological characters, and the variations within populations were much greater than those among populations in most morphological characters. Cluster analysis showed that the five populations of C. microphylla could be divided into two groups in morphological characters, and there was significant positive correlation between the divergence of morphological characters matrix and geographical distance matrix. Principal component analysis showed that leaflet length, area of a compound leaf, fresh-mass of a compound leaf, and shoot fresh-mass were main morphological characters that varied among C. microphylla populations. Spearman correlation analysis showed that there were significant correlations between some morphological characters and soil factors. Soil N:P ratio, available N content, total N content, organic matter content and soil water content were main factors that were associated with morphological characters of C. microphylla.     

Phenotypic plasticity or speciation? A case from a clonal marine organism

Background  

Clonal marine organisms exhibit high levels of morphological variation. Morphological differences may be a response to environmental factors but also they can be attributed to accumulated genetic differences due to disruption of gene flow among populations. In this study, we examined the extensive morphological variation (of 14 characters) in natural populations observed in the gorgonian Eunicea flexuosa, a widely distributed Caribbean octocoral. Eco-phenotypic and genetic effects were evaluated by reciprocal transplants of colonies inhabiting opposite ends of the depth gradient and analysis of population genetics of mitochondrial and nuclear genes, respectively.