Low isozyme diversity in Nordic and central European populations of Vicia pisiformis and V. dumetorum (Fabaceae)

Vicia pisiformis and V. dumetorum are closely related perennial species occurring in small, disjunct populations throughout Europe. In Sweden, they are classified as "vulnerable" and "care-demanding", respectively. They possess low variation in RAPD (Random Amplified Polymorphic DNA) markers but relatively high morphological variation. We estimated the amount and distribution of isozyme diversity within and among marginal (Sweden, Norway) and central (Czech Republic) populations. Vicia dumetorum was monomorphic for all 14 isozyme loci in the 22 populations investigated, whereas V. pisiformis had 2.94 % polymorphic loci and a mean of 1.02 alleles per loci. The differentiation (F_sr) of populations of V pisiformis were 0.848, but no clear geographical pattern was found. Preliminary results from artificial pollination experiments suggests self-compatibility in V. dumetorum . The low overall polymorphism in Swedish and Czech localities in both species is explained in terms of common postglacial colonization events, recent anthropogenic activity, selfing and clonal reproduction. Finally, the implications of the data for conservation genetics is discussed.     

Comparative analysis of genetic diversity of sesame (Sesamum indicum L.) from Vietnam and Cambodia using agro-morphological and molecular markers

The purpose of this study was to comparatively analyze the genetic diversity of sesame (Sesamum indicum L.) using agro-morphological and molecular markers. Twelve sesame populations collected from three regions in Cambodia and Vietnam were used in this study. A high genetic variation was revealed both by agro-morphological and RAPD markers within and among the 12 sesame populations. The range of agro-morphological trait based average taxonomic distance among populations (0.02 to 0.47) was wider than that of RAPD based genetic distance (0.06 to 0.27). The mean distance revealed by agro-morphological markers (0.23) and RAPD markers (0.22) was similar. RAPD based analysis revealed a relatively higher genetic diversity in populations from South Vietnam as compared to the other two regions. Interestingly, populations from this region also had higher values for yield related traits such as number of capsules per plant, number of seeds per capsule, and seed yield per plant suggesting positive correlation between the extent of genetic variation within population and yield related traits in sesame. A highly significant positive correlation (r = 0.88, P < 0.001) was found between agro-morphological and RAPD markers in estimating the genetic distance between populations. Both methods suggested the existence of a substantial amount of genetic diversity both in the Vietnamese and Cambodian populations. Although both agro-morphological and RAPD markers were found to be useful in genetic diversity analysis in sesame, their combined use would give superior results.     

Genetic divergence of climatically marginal populations of Vicia pisiformis on the Scandinavian Peninsula

Vicia pisiformis L. is a perennial leguminous plant with a main distribution in broadleaved forest-steppes of eastern Europe. The species is classified as endangered (EN) according to the IUCN red-lists in both Norway and Sweden, due to severe fragmentation, small population sizes and continuing population decline. The populations on the Scandinavian Peninsula constitute the northern limit of the species distribution and are mostly restricted to warm stony slopes with predominantly southern aspects. In this study we used the AFLP method, which is a high-resolution genetic fingerprint method. Samples were collected from 22 Scandinavian populations. The overall genetic structure was analysed in an AMOVA, in a Mantel test and through constrained correspondence analysis (CCA). The ordination scores representing non-geographic genetic divergence were extracted from the CCA and analysed in a linear model using habitat variables and population size as explanatory variables. We found (i) a strong geographic structure, (ii) significant genetic divergence between populations, (iii) that this genetic divergence remained significant even after removing the effect of geography in a partial CCA and (iv) that the remaining non-geographic part of genetic divergence (distance from the ordination centre) was associated with aspect, populations with a northern aspect were more genetically divergent. Aspect explains more variation than population size and is the only variable retained in the minimal adequate model. We suggest that local adaptation has caused this divergence from an expected geographical pattern of genetic variation. This explanation is further supported by the association between aspect and specific AFLP fragments.     

基于RAPD数据探讨中华蓑藓(Macromitrium cavaleriei Card.& Thér.)形态变异的遗传基础

中华蓑藓(Macromitrium cavaleriei Card.&;Thér.)的形态变异强烈,为了解形态变异是否具有遗传学背景,本研究以采自浙南凤阳山、浙中金华北山、浙西北的天目山和江西庐山4个种群的中华蓑藓为材料,运用随机扩增多态性DNA(RAPD)探讨了中华蓑藓的遗传多样性。从100条随机引物中筛选出了15条有效引物,利用它们共获得183个条带,其中多态性条带占79.69%,中华蓑藓各种群间的Dice遗传距离为0.0732~0.1514。POPGENE32软件分析得到种的Nei基因多样性指数(H)为0.3378,Shannon指数(I)为0.5126,遗传分化系数(G_st)为0.1670;基因流(N_m)为2.4947;种群内遗传多样性指数为0.4055,占种群总的遗传多样性的79.11%,反映出研究区域内的中华蓑藓遗传变异大多数存在于种群内,中华蓑藓形态变异并没有多少遗传背景,很可能是生态环境因素引起的可塑性变异。聚类分析表明,中华蓑藓种群遗传距离与地理距离之间无直接相关关系,遗传多样性水平与物种特性和所处不同群落有关。虽然4个种群内的形态变异丰富,但是属于同一物种的范围。     

基于RAPD数据探讨中华蓑藓(Macromitrium cavaleriei Card. & Thér.)形态变异的遗传基础

中华蓑藓（Macromitrium cavaleriei Card.＆Thér.）的形态变异强烈,为了解形态变异是否具有遗传学背景,本研究以采自浙南凤阳山、浙中金华北山、浙西北的天目山和江西庐山4个种群的中华蓑藓为材料,运用随机扩增多态性DNA（RAPD）探讨了中华蓑藓的遗传多样性。从100条随机引物中筛选出了15条有效引物,利用它们共获得183个条带,其中多态性条带占79·69%,中华蓑藓各种群间的Dice遗传距离为0·0732~0·1514。POPGENE32软件分析得到种的Nei基因多样性指数（H）为0·3378,Shannon指数（I）为0·5126,遗传分化系数（Gst）为0·1670;基因流（Nm）为2·4947;种群内遗传多样性指数为0·4055,占种群总的遗传多样性的79·11%,反映出研究区域内的中华蓑藓遗传变异大多数存在于种群内,中华蓑藓形态变异并没有多少遗传背景,很可能是生态环境因素引起的可塑性变异。聚类分析表明,中华蓑藓种群遗传距离与地理距离之间无直接相关关系,遗传多样性水平与物种特性和所处不同群落有关。虽然4个种群内的形态变异丰富,但是属于同一物种的范围。     

Geographic variation of flower traits in Narcissus papyraceus (Amaryllidaceae): do pollinators matter?

Aim The geographic clinal variation of traits in organisms can indicate the possible causes of phenotypic evolution. We studied the correlates of flower trait variation in populations of a style‐dimorphic plant, Narcissus papyraceus Ker‐Gawl., within a region of high biogeographical significance, the Strait of Gibraltar. This species shows a geographic gradient in the style‐morph ratio, suggested to be driven by pollinator shifts. We tested whether parallel geographic variation of perianth traits also exists, concomitant with vegetative trait variation or genetic similarity of plant populations. Location The Strait of Gibraltar region (SG hereafter, including both south‐western Iberian Peninsula and north‐western Morocco). Methods We used univariate and multivariate analyses of flower and vegetative traits in 23 populations. We applied Mantel tests and partial Mantel correlations on vegetative and flower traits and geographic locations of populations to test for spatial effects. We used Moran’s autocorrelation analyses to explore the spatial structure within the range, and performed the analyses with and without the Moroccan samples to test for the effects of the SG on spatial patterns. Amplified fragment length polymorphism data were used to estimate the genetic distance between populations and to ascertain its relationship with morphometric distance. Results There was high variation between and within populations in both flower and vegetative traits. Mantel correlations between geographic and morphometric distances were not significant, but the exclusion of Moroccan populations revealed some distance effect. Partial Mantel correlation did not detect a significant correlation between flower and vegetative morphometric distances after controlling for geographic distance. There were opposite trends in spatial autocorrelograms of flower and vegetative traits. The genetic distance between pairs of populations was directly correlated with geographic distance; however, flower morphometric and genetic distances were not significantly correlated. Main conclusions The SG had some influence on phenotypes, although the causes remain to be determined. The opposite trend of variation in flower and vegetative traits, and the lack of correlation between genetic distance and dissimilarity of flower phenotypes favour the hypothesis of pollinator‐mediated selection on flower morphology, although this may affect only particular traits and populations rather than overall phenotypes. Although stochastic population processes may have a small effect, other factors may account for the high flower variation within and between populations.     

Genetic diversity of Persian shallot (Allium hirtifolium Boiss.) populations based on morphological traits and RAPD markers

Mooseer or Persian shallot (Allium hirtifolium Boiss.) is a bulbous perennial herb belonging to Alliaceae family. Genetic diversity of 16 mooseer populations collected from different parts of Iran were evaluated using 14 morphological traits as well as antioxidant activities and RAPD markers. Statistical analysis showed significant differences among populations for all morphological traits. In a principal component analysis, four components showed 77.5 % of the total morphological variation. Based on the morphological traits, populations were divided into five groups by clustering. Antioxidant capacities differed among all populations, with the Sahneh and Nahavand populations having the highest and the lowest activities, respectively. Genetic diversity of populations was also investigated through RAPD technique using 14 random primers. Cluster analysis based on RAPD markers plus 47 % coefficient of similarity divided the genotypes into six distinct groups. The highest and lowest similarities between populations were detected to be 0.63 and 0.21, respectively. These results indicated that the assessment of genetic diversity in Iranian mooseer populations could be appropriately carried out using RAPD technique which correlates with morphological traits.     

Genetic variation for growth,morphological, and physiological traits in a wild population of the Neotropical shade­tolerant rainforest tree <Emphasis Type="BoldItalic">Sextonia rubra</Emphasis> (Mez) van der Werff (Lauraceae)

Quantitative genetic diversity is a fundamental component of the interaction between natural populations and their environment. In breeding programmes, quantitative genetic studies on tropical trees have so far focused on fast-growing, light-demanding species, but no information exists on shade-tolerant, slow-growing species. For this study, 27 3-year-old open-pollinated families of the Neotropical shade-tolerant rainforest tree Sextonia rubra were measured in semicontrolled conditions for 20 morphological, growth, and photosynthesis traits; the effect of genetic relatedness, habitat of provenance, and mother tree status on seedling traits was analysed. Nine traits displayed significant genetic effects, while mother tree status and habitat effects were not significant (P > 0.05) for an y trait. Estimated heritability varied between 0.14 and 0.28, with growth-related traits having the highest values. Additive genetic variation correlated positively with nonheritable variation, suggesting that ecological–evolutionary factors increasing or decreasing additive genetic variance may also affect nonheritable variation in the same direction. Our results suggest that quantitative genetic variability should be taken into account in ecological studies on, and in the management of, natural tropical rainforests; further research is needed to investigate genetic × environment interactions, in particular from the point of view of the genetic response of shade-tolerant plant species to variations in light availability.     

Divergent selection along climatic gradients in a rare central European endemic species,Saxifraga sponhemica

Background and Aims The effects of habitat fragmentation on quantitative genetic variation in plant populations are still poorly known. Saxifraga sponhemica is a rare endemic of Central Europe with a disjunct distribution, and a stable and specialized habitat of treeless screes and cliffs. This study therefore used S. sponhemica as a model species to compare quantitative and molecular variation in order to explore (1) the relative importance of drift and selection in shaping the distribution of quantitative genetic variation along climatic gradients; (2) the relationship between plant fitness, quantitative genetic variation, molecular genetic variation and population size; and (3) the relationship between the differentiation of a trait among populations and its evolvability.Methods Genetic variation within and among 22 populations from the whole distribution area of S. sponhemica was studied using RAPD (random amplified polymorphic DNA) markers, and climatic variables were obtained for each site. Seeds were collected from each population and germinated, and seedlings were transplanted into a common garden for determination of variation in plant traits.Key Results In contrast to previous results from rare plant species, strong evidence was found for divergent selection. Most population trait means of S. sponhemica were significantly related to climate gradients, indicating adaptation. Quantitative genetic differentiation increased with geographical distance, even when neutral molecular divergence was controlled for, and Q_ST exceeded F_ST for some traits. The evolvability of traits was negatively correlated with the degree of differentiation among populations (Q_ST), i.e. traits under strong selection showed little genetic variation within populations. The evolutionary potential of a population was not related to its size, the performance of the population or its neutral genetic diversity. However, performance in the common garden was lower for plants from populations with reduced molecular genetic variation, suggesting inbreeding depression due to genetic erosion.Conclusions The findings suggest that studies of molecular and quantitative genetic variation may provide complementary insights important for the conservation of rare species. The strong differentiation of quantitative traits among populations shows that selection can be an important force for structuring variation in evolutionarily important traits even for rare endemic species restricted to very specific habitats.     

濒危灌木长叶红砂遗传多样性的RAPD分析

应用RAPD分子标记对濒危灌木长叶红砂(Reaumuria trigyna)种群遗传多样性进行了分析.应用18条随机引物对长叶红砂5个种群的95个个体进行扩增,检测到118个位点,其中多态位点105个.结果表明:长叶红砂种群的多态位点比率(P)为88.98%,显示出长叶红砂种群存在较高的遗传多样性.Shannon多样性指数(0.4966)、Nei基因多样性指数(0.3303)和基因分化系数(Gst=0.1425)的分析结果显示,长叶红砂种群遗传变异大多存在于种群内,种群间的遗传分化占14.25%.聚类分析表明,长叶红砂种群遗传距离与地理距离之间无直接相关关系.遗传多样性水平与物种特性和所处不同群落有关,濒危植物并不一定表现为遗传变异水平的降低.     

Genetic variation in Arabidopsis suecica and its parental species A. arenosa and A. thaliana

Random amplified polymorphic DNA (RAPD) markers were used to estimate the level of genetic variation in Swedish accessions of the allopolyploid Arabidopsis suecica and its parental species A. thaliana and A. arenosa. The results showed clear differences among the three species with respect to the level of variation. A. arenosa was highly variable, A. thaliana showed a moderate level of variation whereas A. suecica was much less variable than the two other species. An extended analysis covering 19 Swedish populations of A. suecica corroborated the low level of variation in this species, yet 16 unique phenotypes were observed. No isolation by distance was observed. When the genetic variation was partitioned among and within populations of A. suecica, the results showed that the majority of the variation (81%) occurred among populations. This result is interpreted as a strong indication that A. suecica is autogamous in nature.     

Morphological and molecular diversity among Italian populations of Quercus petraea (Fagaceae)

Quercus petraea (sessile oak) has a scattered distribution in southern and central Italy. The objective of this work was to evaluate the level and distribution of diversity in five Italian populations of Q. petraea by using morphological markers and hypervariable molecular markers such as microsatellites. Forty-eight morphological traits and six nuclear and three plastid loci were scored for each population. Evidence for differentiation in both sets of traits was found, but patterns of differentiation of morphological traits did not coincide with microsatellite differentiation. Morphological variation was correlated with ecological conditions at the site of origin. Analysis of molecular variance revealed significant genetic variation among populations (P < 0.001), both at the nuclear and plastid levels. There was a slight, but significant, correlation between nuclear genetic distance and geographic distance. The relatively high genetic diversity in the populations analysed indicates that the maintenance of their evolutionary potential is possible if population sizes are maintained or increased. Low levels of haplotype diversity found within the small southernmost population (Piano Costantino) indicates that genetic erosion may increase the extinction risk for this population.     

Patterns of genetic variation in Gymnadenia conopsea, the fragrant orchid

Gymnadenia conopsea (L.) R. Br., or the fragrant orchid, is one of many plant species negatively influenced by new practices in agriculture and forestry during the last decades. This study describes the level of microsatellite variation within and among 10 Swedish populations of this species. It was not possible to detect strong effects of small population size or fragmentation. In general, the species had high genetic variation within and low genetic divergence among populations, although the correlation between population size and number of alleles was close to significance at the 95% level. Also, a significant isolation by distance effect was observed, indicating the presence of modest restrictions in gene dispersal between the investigated populations.     

Exploring the impact of neutral evolution on intrapopulation genetic differentiation in functional traits in a long-lived plant

Most plant species, particularly long-lived plants, harbor a large amount of genetic variation within populations. A central issue in evolutionary ecology is to explore levels of genetic variation and understand the mechanisms that influence them. In this study, our goals were to examine the impact of neutral evolutionary processes on the genetic variance and functional diversity within three populations of a long-lived plant (Quercus suber L.). For this purpose, we genotyped the progeny of 45 open-pollinated mother trees from three populations originating from Spain, Portugal, and Morocco using six microsatellite markers. Seedlings were planted in a common garden trial and were phenotypically characterized by seven leaf functional traits. Molecular analyses revealed weak genetic differences between Iberian and Moroccan populations. Nevertheless, high genetic differentiation was observed among maternal families within populations. Differentiation between particular maternal families from the same population reached values of 29.2 %, which far exceeds the values reported between the most genetically distant populations for this species (11.7 %). Maternal families differed also in phenology, leaf size, and shape traits. In the Moroccan population, there were correlations among matrices of distances for molecular markers, leaf shape traits (e.g., leaf circularity index), and phenology, indicating that maternal families with contrasting phenologies were genetically and functionally distinct. This, together with the moderate heritability for phenology in Moroccan population, suggests that besides selective forces, neutral evolutionary processes have promoted intrapopulation genetic divergence and contribute to maintain high levels of genetic variation within this population. Overall, our results reinforce the importance of intrapopulation studies in long-lived plants under an evolutionary context.     

Identification and genetic variation among Hibiscus species (Malvaceae) using RAPD markers

Germplasm identification and characterization is an important link between the conservation and utilization of plant genetic resources. Traditionally, species or cultivars identification has relied on morphological characters like growth habit or floral morphology like flower colour and other characteristics of the plant. Studies were undertaken for identification and determination of genetic variation within the two species of Hibiscus and 16 varieties of Hibiscus rosa-sinensis L. through random amplified polymorphic (RAPD) markers. Primer screening was made by using the DNA of variety "Prolific". Genetic analysis was made by using ten selected decamer primers. A total of 79 distinct DNA fragments ranging from 0.3 to 2.5 kb were amplified by using ten selected random decamer primers. The genetic similarity was evaluated on the basis of presence or absence of bands. The cluster analysis indicated that the 16 varieties and two species formed one cluster. The first major cluster consisted of three varieties and a second major cluster consisted of two species and 13 varieties. The genetic distance was very close within the varieties and also among the species. Thus, these RAPD markers have the potential for identification of species/varieties and characterization of genetic variation within the varieties. This is also helpful in Hibiscus breeding programs and provides a major input into conservation biology.     

Extreme ecological and phenotypic differences in the tropical tree chicozapote (Manilkara zapota (L.) P. Royen) are not matched by genetic divergence: a random amplified polymorphic DNA (RAPD) analysis

The chicozapote ( Manilkara zapota ) is a tropical fruit tree that occurs in two morphologically distinct populations in the Yucatan peninsula of Mexico. Forest populations consist of tall, straight trees, while swamp populations have a short, shrub-like growth form. Swamp populations also have smaller leaves, fruit and seeds. We performed a random amplified polymorphic DNA (RAPD) analysis on four different populations of chicozapote to test if there was a genetic component to this variation. The populations differed in respect to habitat type (swamp vs. forest) and geographical location (east vs. west). We surveyed 80 random primers, nine of which revealed interpopulation band differences (28 band differences in total). Unweighted pair group method analysis ( UPGMA ) and neighbour-joining dendrograms showed no separation of individuals between the different populations. Analysis of the RAPD data showed no significant differences between swamp and forest populations ( P > 0.1). The lack of genetic differentiation suggests a failure to find a correlation between the RAPD loci and adaptive traits. The observed morphological differences between the swamp and forest populations of chicozapote may either be that gene flow has prevented a build-up of neutral marker differences or a plastic response to differences in habitat.     

内蒙古中东部草原羽茅内生真菌的遗传多样性

该文从形态学和基因水平上对内蒙古中东部草原4个羽茅(Achnatherum sibiricum)种群所含的27个内生真菌(Neotyphodium)菌株的遗传多样性进行了研究,结果表明羽茅内生真菌在形态学和基因水平上均表现出较高的遗传多样性。在PDA培养基上,根据菌落颜色、质地、生长速率和分生孢子外观等特征,可分为4个形态型;西乌旗、霍林郭勒和定位站3个种群所含的内生真菌菌落具有相似的生长特性和外观,而羊草(Leymus chinensis)样地种群无论从菌落外观和质地的多样性,还是遗传多样性指数均高于其它3个样地。用20个随机引物对这27株内生真菌基因组DNA进行RAPD分析,共检测到463个位点,其中461个为多态位点,多态位点百分率达99.6%,特有位点93个,占20.1%。Nei基因多样性指数h和Shannon多样性指数I分别为 0.238 0和0.387 0;多数菌株间的遗传一致度较低而遗传距离较大,在DNA水平上存在较显著的遗传变异。基于Nei无偏遗传距离和UPGMA法的聚类分析结果将27株内生真菌分为7组,并且与形态型的划分基本一致,RAPD分析方法提高了内生真菌类群划分的可靠性。     

Evolution and ecology meet molecular genetics: adaptive phenotypic plasticity in two isolated Negev desert populations of Acacia raddiana at either end of a rainfall gradient

Background and Aims

The ecological, evolutionary and genetic bases of population differentiation in a variable environment are often related to the selection pressures that plants experience. We compared differences in several growth- and defence-related traits in two isolated populations of Acacia raddiana trees from sites at either end of an extreme environmental gradient in the Negev desert.

Methods

We used random amplified polymorphic DNA (RAPD) to determine the molecular differences between populations. We grew plants under two levels of water, three levels of nutrients and three levels of herbivory to test for phenotypic plasticity and adaptive phenotypic plasticity.

Key Results

The RAPD analyses showed that these populations are highly genetically differentiated. Phenotypic plasticity in various morphological traits in A. raddiana was related to patterns of population genetic differentiation between the two study sites. Although we did not test for maternal effects in these long-lived trees, significant genotype × environment (G × E) interactions in some of these traits indicated that such plasticity may be adaptive.

Conclusions

The main selection pressure in this desert environment, perhaps unsurprisingly, is water. Increased water availability resulted in greater growth in the southern population, which normally receives far less rain than the northern population. Even under the conditions that we defined as low water and/or nutrients, the performance of the seedlings from the southern population was significantly better, perhaps reflecting selection for these traits. Consistent with previous studies of this genus, there was no evidence of trade-offs between physical and chemical defences and plant growth parameters in this study. Rather, there appeared to be positive correlations between plant size and defence parameters. The great variation in several traits in both populations may result in a diverse potential for responding to selection pressures in different environments.     

Molecular Genetic Variation in a Clonal Plant Population of Leymus chinensis (Trin.) Tzvel.

Randomly amplified polymorphic DNA (RAPD) analysis was used to investigate the genetic variation among populations, between populations, and within populations, relationships between genetic distance and geographic distance, and the molecular variation and population size. The effects of geographic and genetic distances, as well as of genetic differentiation and population size, on genetic variations of Leymus chinensis (Trin.) Tzvel. are discussed. The present study showed that there was significant RAPD variation between the Baicheng region population and the Daqing region population, with a molecular variance of 6.35% (P ＜ 0.04), and for differentiation among area populations of the Daqing region, with a molecular variance of 8.78% (P ＜ 0.002). A 21.06% RAPD variation among all 16 populations among two regions was found (P ＜ 0.001), as well as 72.59% variation within populations (P ＜ 0.001). Molecular variation within populations was significantly different among 16 populations.