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。     

Genetic variation in five Mediterranean populations of Juniperus phoenicea as revealed by inter-simple sequence repeat (ISSR) markers

BACKGROUND AND AIMS: The assessment of the genetic variability and the identification of isolated populations within a given species represent important information to plan conservation strategies on a genetic basis. In this work, the genetic variability in five natural populations of Juniperus phoenicea, three from Sardinia, one from Cyprus and the last one in the Maritime Alps was analysed by means of ISSRs, on the hypothesis that the latter could have been a refugial one during the last glaciation. METHODS: ISSRs were chosen because of their ability to detect variation without any prior sequence information. The use of three primers yielded 45 reproducible, polymorphic bands, which were utilized to estimate the basic parameters of genetic variability and diversity. KEY RESULTS: All of the populations analysed harboured an adequate amount of genetic variability, with H(S) = 0.1299. The proportion of genetic diversity between populations has been estimated by G(ST) = 0.12. The three Sardinian populations are separated, as tested by AMOVA, from the Cyprus and the continental ones. CONCLUSIONS: The results indicate that geographical isolation has represented a major barrier to gene flow in Juniperus phoenicea. This work represents a first step towards a full genetic characterization of a conifer from the Mediterranean, a world biodiversity hotspot confronted with climate change, and thus contributes towards the planning of genetics-informed conservation strategies.     

Demographic and spatial analysis of a population of Juniperus oxycedrus L. in an abandoned grassland

A study of the structural, dynamic, and space occupancy characteristics of a prickly juniper (Juniperus oxycedrus) population developed on an abandoned secondary grassland of the Central Apennines (Italy), is presented here. The data were collected from a permanent plot, limited by mixed deciduous woods dominated by Ostrya carpinifolia Scop. by a plantation of Pinus nigra Arnold, and by a forest road, and consisting of 1744 prickly juniper individuals, as well as other pre-forest and forest species. The age and sex distributions of this population were assessed. With these data, the age pyramid was constructed, within which three developmental phases of the population became apparent, as confirmed by a study of the logistic curve of development of the population. Based on an estimate of the intensity function of the spatial distribution of the prickly juniper individuals, the hypothesis of complete randomness has to be rejected. On the other hand, the correlation between sex and population density was significant. The mode of space occupancy of the prickly juniper population was investigated also with respect to the other populations of shrubs and forest species. It was shown to spread out in all directions, following lines of diffusion that could be randomly determined. Finally, the presence, within the plot, of some pasture areas not occupied by prickly juniper may be derived from lack of germination of the fruits, or development of the seedlings owing to unfavourable micro-environmental conditions.     

Phenotypic variation and stress resistance in core and peripheral populations of Hordeum spontaneum

The phenotypic variation and response of plants to water stress were studied in a field trial in populations of wild barley, Hordeum spontaneum Koch. from Israel and Turkmenistan. Populations from the species distributional core and periphery were compared and contrasted for phenotypic variation in 16 phenological and morphological traits. The peripheral populations (six) were found to be phenotypically more variable and more resistant to water stress than core populations (12). The association of water-stress resistance with high phenotypic variability gives support to the hypothesis that populations that are genetically more variable are better adapted or pre-adapted to environmental changes and are thus valuable for conservation.     

High levels of genetic diversity in marginal populations of the marsh orchid Dactylorhiza majalis subsp. majalis

Because of harsh conditions, suboptimal habitat quality and poor connectivity to other populations, plant populations at the margin of a distribution are expected to be less genetically diverse, but to be more divergent from each other than populations in the centre of a distribution. In northern Europe, northern marginal populations may also be younger than populations further to the south, and may have had less time to accumulate genetic diversity by mutation and gene flow. However, orchids have very small seeds, which are easily dispersed long distances by wind, and orchids are therefore expected to show less differentiation between marginal and central populations than other groups of seed plants. Here, we analysed whether Scandinavian populations of the tetraploid marsh orchid Dactylorhiza majalis subsp. majalis differ from central European populations in genetic diversity patterns. A total of 220 plants from eight central European and ten Scandinavian populations was examined for variation at five nuclear microsatellite loci, nuclear ITS and 13 polymorphic sites in noncoding regions of the plastid genome. The total genetic diversity was slightly lower in Scandinavia than in central Europe, both in plastid and nuclear markers, but the differences were small. Also, the Scandinavian populations were less diverse and somewhat more strongly differentiated from each other than the central European ones. Dactylorhiza majalis subsp. majalis has apparently colonized Scandinavia on multiple independent occasions and from different source areas in the south. Seed flow between Scandinavian populations has still not fully erased the patterns imprinted by early colonization. Our results suggest that marginal populations of orchids may be as important as central ones in preserving genetic diversity through Pleistocene glacial cycles. We also predict that orchids with their light seeds are better adapted than many other plants to respond to future climate changes by dispersing into new suitable areas.     

Alkane composition diversity among populations of dwarf forms of Juniperus communis L.: comparison between western Europe and northern American populations

The cuticular wax composition of leaves has been analysed in three western European populations (Corsica, central Pyrenees, northern Alps) of Juniperus communis var. saxatilis Pall. (=  J. nana Willd., nom illeg.) and in one population of J. communis L. var. depressa Pursh. from North America (Sierra Nevada). Gas chromatography shows the presence of 13 alkanes in all samples ranging from C₂₃ to C₃₅ with important intraspecific polymorphism in alkane content. The dominant alkanes range from C₃₃ to C₃₅. Alkanes C₂₁ and C₂₂ were found only in Corsica and Sierra Nevada populations. Canonical discriminant analysis separated the J. communis L. var. depressa Pursh. of the population of Sierra Nevada from other populations of J. communis var. saxatilis Pall. on the basis of their higher C₃₁ content and the constant presence of C₂₁ and C₂₂ alkanes. J. communis var. saxatilis Pall. populations from the Pyrenees are close to northern Alps populations characterized by high concentrations of C₃₃, C₃₄ and C₃₅ alkanes. This paper confirms the existence of Juniperus var. saxatilis Pall. in the Pyrenees (France).  © The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 140 , 165–168.     

Genetic divergence among geographical populations of the migratory locust in China

The random amplified polymorphic DNA (RAPD) technique was used to examine genetic divergence and interrelations of 11 geographical populations of the migratory locust in China, and the role of spatial separation in the population differentiations. AMOVA analysis of genetic variations in all the populations indicated greater within- (79.55%) than among-population variability (20.45%), and that there were significant differentiations among the populations; 11 populations were divided into four regional groups, with significantly greater variability within (82.99%) than among the groups (17.01%), and there existed apparent regional differentiations. Paired comparisons showed significantly greater variability within-than between-groups, indicating significant differentiations between populations of different regional groups. Of all the pairwise comparisons, Hainan and Tibetan groups displayed the greatest differentiation, with the difference between the two groups being seven folds of that between populations within the groups; the least differentiations were exhibited between the groups of Hainan, Xinjiang, and Inner Mongolia, with the differences between groups being only half of the differences between populations within the groups. Mantel tests of the genetic and spatial distances showed that the two matrices were significantly correlated (p<0.01), indicating that the geographical isolation played an important role in the differentiations of the geographical populations of the migratory locusts. Cluster analysis divided all populations into four major groups: Xinjiang and Inner Mongolia group, the Great Plains of North China (the Yellow River and Huai River Plains) group, Hainan group, and Tibet group. Principal component analysis (PCA) supported the division of populations based on the cluster analysis. However, analysis of individuals clustered the locusts into five populations: Xinjiang and Inner Mongolia, Hami in Xinjiang, the Great Plains of North China, Hainan, and Tibet. The locust populations in eastern China displayed apparently continous and gradient variations; as such authors consider that there were no necessity and valid reasons for further division of subspecies. The subspecific status for the main geographical populations of the migratory locusts in China was discussed.     

Craniometric variation in Norwegian wolverines Gulo gulo L.

Craniometric variation in Norwegian wolverines was analysed using univariate and multivariate techniques. The wolverine skull seems to be full-grown after about 9 months in both sexes although some dimensions continued to grow at a slow rate after the first year. Size allometry was studied in skulls older than 11 months. Allometric coefficients were calculated from different methods. The multivariate allometric coefficients were found to reflect the same allometric patterns as were found from the reduced major axis and from the direction cosines of PCI, whereas the coefficients seem to be underestimated by the least-square regression method. Sexual dimorphism was found to be highly significant, males being the larger sex. The female skulls were found to be relatively broader and to have a relatively higher coronoid process than the male skulls. It seems that the females have a relatively stronger feeding apparatus than the males, which leads to less absolute differences in strength, as reflected in a very high degree of dietary overlap. Two discriminant functions were calculated which both classified the material into their correct sex with nearly 100% accuracy. Geographical variation between samples from Nordland and Finnmark counties were studied. No significant multivariate variation was found between the female skulls. The male variation was highly significant; the Nordland skulls seem to have longer carnassials than those from Finnmark.     

Craniometric variation in Norwegian wolverines Gulo gulo L.

Craniometric variation in Norwegian wolverines was analysed using univariate and multivariate techniques. The wolverine skull seems to be full-grown after about 9 months in both sexes although some dimensions continued to grow at a slow rate after the first year. Size allometry was studied in skulls older than 11 months. Allometric coefficients were calculated from different methods. The multivariate allometric coefficients were found to reflect the same allometric patterns as were found from the reduced major axis and from the direction cosines of PCI, whereas the coefficients seem to be underestimated by the least-square regression method. Sexual dimorphism was found to be highly significant, males being the larger sex. The female skulls were found to be relatively broader and to have a relatively higher coronoid process than the male skulls. It seems that the females have a relatively stronger feeding apparatus than the males, which leads to less absolute differences in strength, as reflected in a very high degree of dietary overlap. Two discriminant functions were calculated which both classified the material into their correct sex with nearly 100% accuracy. Geographical variation between samples from Nordland and Finnmark counties were studied. No significant multivariate variation was found between the female skulls. The male variation was highly significant; the Nordland skulls seem to have longer carnassials than those from Finnmark.     

Genetic divergence among geographical populations of the migratory locust in China

The migratory locust, Locusta migratoria L., which is distributed widely in the East Hemisphere, has long been regarded as the most important agricultural pest and a model insect. Its distribution ranges from thetropic and the subtropical zone, to the temperate zone, and to the cold-temperate zone. Because of the wide geographical distribution and adaptations, many geo- graphical populations of the migratory locust dis- played apparent variation in morphology, life history, physiology, and ot…     

Adaptive variation in head size in Vipera berus L. populations

To prove that predators are morphologically adapted to the size of their prey one has to demonstrate that the morphological variation in the trophic apparatus is related to the prey size distribution and that the variation in the trait has some effect on individual fitness. I have studied geographic variation in relative head length (RHL) of adders, Vipera berus , on the Swedish mainland and on groups of islands in the Baltic Sea, and the relationship between RHL and physical condition, a character related to fitness. I also examined the relationship between RHL and sex and colour morph. Relative head length of adders was smallest on the mainland and increased on the islands with increasing body size of the main prey, Microtus agrestis , suggesting stabilizing selection for head size within each population. There was no difference in RHL between sexes or colour morphs. However, physical condition was positively correlated with RHL, indicating directional selection for larger heads. The observed pattern is interpreted as an evolutionary response to the geographic variation in body size of the main prey species and the smaller number of alternative prey species available on islands.     

Leaf morphometric variation in Quercus affinis and Q. laurina (Fagaceae), two hybridizing Mexican red oaks

Leaf variation was examined in two hybridizing Mexican red oaks, Quercus affinis and Q. laurina . Data of nine traits were obtained for ten randomly chosen leaves in each of 512 individuals from 16 populations sampled along a geographical gradient, including the distribution area of both species and a putative area of secondary contact and hybridization. A cluster analysis recognized two main groups of populations, which were congruent with the taxonomic assignment of the predominant morphological type within the populations and were thus labelled ' Q. affinis -like' and ' Q. laurina -like' population groups. A nested analysis of variance revealed that the largest proportion of the total variation was contained within populations, as among-tree variation (28–54%, depending on the trait), and as intra-individual variation (17–56%). However, differences between the two groups of populations (3–27%) and among populations within groups (5–21%) were also significant for the nine traits. A distinct pattern of change across populations was observed for each trait. Variation was particularly pronounced along the geographical gradient for petiole length and leaf-margin teeth number, possibly implying selection on these two traits. Results suggest that phenotypic plasticity, gene flow, hybridization and natural selection have shaped foliar variation in this oak complex. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 147 , 427–435.     

Genetic variation and population structure of cod, Gadus morhua L., in some fjords in northern Norway

Biochemical genetic polymorphism in cod from several fjords in Troms, northern Norway was analysed. Gene frequencies at several polymorphic loci ( Hb, Pgi, Ldh, Pgm, Gpd and Idh ) are given. Significant variation was found both within and between fjords, and even between samples from the same locality sampled in different years, indicating a mosaic structure of the cod population in the area studied. The results of the haemoglobin variation are compared to similar results obtained more than 20 years ago in the same and adjacent areas. The biochemical genetic variation is discussed in relation to stability of gene frequencies, isolation mechanisms and migration patterns.     

Spring phenology shows genetic variation among and within populations in seedlings of Scots pine (Pinus sylvestris L.) in the Scottish Highlands

Background: Genetic differentiation in phenotypic traits is often observed among forest tree populations, but less is known about patterns of adaptive variation within populations. Such variation is expected to enhance the survival likelihood of extant populations under climate change.

Aims: Scots pine (Pinus sylvestris) occurs over a spatially and temporally heterogeneous landscape in Scotland. Our goal was to examine whether populations had differentiated genetically in timing of bud flush in response to spatial heterogeneity and whether variation was also maintained within populations.

Methods: Two common-garden studies, involving maternal families of seedlings from 21 native pinewoods, were established and variation in the trait was measured at the beginning of the second growing season.

Results: Populations showed genetic differences in the trait correlated with the length of growing season at their site of origin, but the majority of variation was observed within populations. Populations also differed in their levels of variation in the trait; a pattern that may be influenced by spatial variation in the extent of temporal climate variability.

Conclusions: Our findings suggest that populations have adapted to their home environments and that they also have substantial ability to adapt in situ to changes in growing season length.     

Seasonal morphometric variation in sexual and asexual, North American and Australian, populations of the aphid, Acyrthosiphon pisum

The lengths of the body and appendages of the aphid Acyrthosiphon pisum (Harris) (Homoptera: Aphididae) vary seasonally in sexual North American and asexual Australian populations. The first generation of spring aphids in North America and winter aphids in Australia have short appendages in relation to body length. Excluding this phenotype, North American and Australian aphids cannot be discriminated morphometrically. The short appendages in North America are associated with a specialized morph called a fundatrix; the short appendages of Australian aphids are caused by exposure to low temperatures during prenatal development. The same temperature-sensitive mechanism operates in sexual and asexual North American aphids, but does not explain the short appendages of the fundatrix, which appear to arise through a separate mechanism. The short appendages are caused neither by a maternal effect from winged mothers, although such an effect exists, nor by seasonal changes in body length and allometry, nor by microevolutionary changes. The temperature-induced shortening of appendages is a seasonal polymorphism, which mimics the short appendages seen in fundatrices. The two types of phenotypic plasticity have the same consequence in sexual and asexual populations of the same species and may be an example of convergent evolution.     

天山北部拟南芥自然居群表型变化的环境依赖特征

拟南芥(Arabidopsis thaliana)是植物生物学的模式植物, 在分子遗传学方面已经积累了丰富的研究成果, 但目前对拟南芥自然分布的生境特点、表型变化的环境依赖特征等研究很少, 极大地限制了对拟南芥进化动力和机制的理解。为了了解在微环境下拟南芥种群分布和表型性状的变化特点, 对天山北部分布于塔尔巴哈台山、阿尔泰山和天山的10个拟南芥种群的分布特征、表型的变化特点, 以及与综合环境因子的相互关系进行了分析。结果表明: 除分枝数外, 株高、株重、根重、单个果实重量、单株果数、单株果重、果长、果实开裂力度、单株果重/总重9个特征在种群间变化显著, 可塑性能力较强; 但方差分析和变异系数结果显示, 角果长度、果实开裂力度在种群内和种群间的变化相对较小。表型特征在山系间、经纬度和海拔间的变化规律不明显。拟南芥主要分布于pH值和HCO₃ ^-含量低, 有机质丰富, 且有一定坡度的沙土地块上。种群内拟南芥分布频度很低, 在1.56%-10.69%之间, 空间自相关距离在15.4-46.7 cm之间变化较大, 10个种群均呈现极显著集群分布, 分布的集群性受果实开裂力度的影响显著, 而果实开裂力度随环境胁迫而极显著增加。总结认为: 天山北部拟南芥生长和分布主要受微环境的影响, 在干旱环境下, 拟南芥主要通过增加繁殖分配比例, 产生难开裂的果实, 促使种子短距离扩散于母株周围, 确保子代利用原适宜生境来生存繁衍。     

Allozyme diversity and genetic structure of marginal and central populations of Corylus avellana L. (Betulaceae) in Europe

Corylus avellana L. (hazel, Betulaceae) is a long-lived, widespread shrub in Europe, having its northern range margin in Fennoscandia and a postglacial history involving range-expansion from refugial areas in southern Europe. In this study, we tested for a relationship between marginality and low within-population genetic diversity by assessing patterns of variation at 14 putatively neutral allozyme loci (comprising 43 putative alleles) within and between 40 natural populations of C. avellana along a north-south transect in Europe. Geographically marginal populations (central Sweden) showed lower levels of within-population diversity than populations in more central regions, as indicated by significant negative correlations between latitude and the percentage of polymorphic loci (r_S=–0.47, P < 0.001), the average number of alleles per locus (r_S=–0.65, P < 0.001), the expected heterozygosity (r_S=–0.19, P < 0.05), and the proportion of distinguishable genotypes (r_S=–0.56, P < 0.001). These patterns, combined with the unusually high between-population component of gene diversity (G_ST=19.7%) and allelic richness (A_ST=24%) in the marginal region, can be attributed to historical bottlenecks during the species postglacial range-expansion, but may also reflect a history of genetic drift in the small, isolated populations occupying the marginal region. Information on the spatial distribution of genotypes provide further support for a role of vegetative reproduction (layering) in the structuring of genetic variation within populations.     

Morphological variation in Plantago lanceolata L.: effects of light quality and growth regulators on sun and shade populations

The effects of different ratios of red to far-red light (R/FR-ratio) and of exogenously applied growth regulators on the morphology of plants from sun and shade populations were studied. Large differences in growth form were found between populations adapted to either sun or shaded habitats. Low R/FR-ratios, simulating vegetation shade, induced a growth form similar to that of plants from the shade population. High R/FR-ratios, simulating sunlight, had the opposite effect. Most morphological differences between shade and sun populations and effects of low R/FR-ratios on growth form could be mimicked by exogenously applied gibberellin (GA₃). In contrast, application of a gibberellin inhibitor (CCC) induced a growth form similar to that of the sun population and of plants grown under a high R/FR-ratio. Interactions between genetic background, the R/FR-ratio, and hormone treatment, were small and the factors exerted their action independently. The results are discussed in relation to the influence of developmental constraints on the evolvability of optimal phenotypes and the plastic responses therein.     

薏苡属的遗传变异性及核型演化

在广泛收集我国薏苡（ＣｅｒｘＬ．）种质资源,进行田间栽培,杂交试验和细胞学观察的基础上,讨论薏苡属植物的遗传多样性、地理分布及种类划分,在原１种２变种的分类基础上,把我国的薏苡属植物划分为３种４变种。根据这些种类的１８个栽培及野生类型的染色体核型演化散点图并结合总苞性状,探讨了该属可能的系统演化关系。     

Clonality and genetic variation in Amylostereum areolatum and A. chailletii from northern Europe

Genetic variation within and between vegetative compatibility groups (VCGs) of Amylostereum areolatum (Fr.) Boid. and Amylostereum chailletii (Pers.: Fr.) Boid. isolates was investigated. DNA fingerprints were made using the M13 core sequence as a primer. A total of 53 isolates of A. areolatum and 57 isolates of A. chailletii from Lithuania, Sweden, Denmark and Great Britain were studied. In all cases isolates belonging to the same VCG showed identical DNA banding patterns, suggesting that VCGs correspond to clones. In A. areolatum the vast majority of the isolates (spread by Sirex juvencus L.) were assigned to dispersive clones, that have wide geographical distribution (i.e. the same genotypes were detected in Lithuania, Sweden and Denmark), with low genetic variation between the different clones. By contrast, A. chailletii population structure was consistent with the spread of airborne basidiospores produced by outcrossing. Only a small fraction of A. chailletii isolates studied, could be assigned to dispersal clones with a local distribution, spread by Urocerus gigas L. Overall, M13 fingerprinting detected low genetic differentiation in both species in the samples we studied.