蒙古栎,辽东栎的遗传分化：从形态到DNA

通过植物群落结构、壳斗、叶脉形态特征、同工酶及ＤＮＡ等多方面调查与测定,分析了帽儿山的蒙古栎（ＱｕｅｒｃｕｓｍｏｎｇｏｌｉｃａＦｉｓｃｈ．）和东灵山、关帝山的辽东栎（Ｑ．ｌｉａｏｔｕｎｇｅｎｓｉｓＫｏｉｄｚ．）的遗传分化及多样性。各种水平的研究一致说明：两种植物的遗传分化较小,东灵山种群是典型蒙古栎、辽东栎种群的中间类型。确切地说,从东北到山西组成一个地理渐变群,存在大范围、强大的双向基因流     

Study on DNA Diversity of Liaodong Oak Population at Dongling Mountain Region,Beijing

Random amplified polymorphic DNA(RAPD) and DNA amplification fingerprinting (DAF) markers were used in detecting genetic structure and DNA diversity of two Liaodong oak ( Quercus liaotungensis Koidz. ) populations at Dongling mountain region, a suburb of Beijing City. Shannon's index of phenotypic diversity was used to partition diversity into components within and between populations. Two hundred and five bands from twelve primers were analyzed. The results showed very high genetic variability within the Liaodong oak populations. The diversity in the central population was higher than that of the marginal one. 95 % of total genetic diversity occurred within populations and the coefficient of gene differentiation was 0.05. Significant difference of gene frequency has been detected in a few loci between populations. The study of different age groups of the oak trees implied that deforestation exerted certain impacts on the genetic structure of the Liaodong oak.     

A Preliminary Study on Genetic Structure of Liaodong Oak (Quercus liaotungensis) Populations in Dry and Moist Habitats and It's Adaptive Implications

The genetic structure of two Liaodong oak (Ouercus liaotungensis Koiz. ) populations whose habitats represent respectively moist and dry donditions at Dongling Mountain region, a suburb of Beijing City, was studied by using isozyme analysis. Thirty putative loci from thirteen enzyme systems were analyzed. The result showed very high genetic variability in the two populations, with a percentage of polymorphic loci of 86.6%, and an average number of alleles per locus of 2.25. There still existed obvious differences in a few loci although high levels of genetic similarity was observed, indicated by low value of both distance (D= 0. 029) and coefficient of gene differentiation (GsT = 0. 048). The dynamic changes of the gene frequencies of different age groups of oak trees may imply that the oak populations can be adaptive to different conditions.     

Genetic variation and differentiation in population of Japanese emperor oak (Quercus dentata Thunb.) and Mongolian oak (quercus mongolica fisch. ex ledeb.) in the south of the Russian far east

Allozyme variation of Japanese emperor oak Quercus dentata Thunb. and Mongolian oak Quercus mongolica Fisch. ex Lebed.) was examined in 11 populations of these species from southern Primorye. Analysis of 18 loci showed that in these populations, 66.7% of genes of Mongolian oak are polymorphic, the number of alleles per locus being 2.28. In Japanese emperor oak, these parameters were respectively 59.8 and 2.36%. The observed heterozygosity in both species did not differ from the expected values, constituting 0.198 in Japanese emperor oak and 0.161 in Maongolian oak. The Nei's distance between Quercus mongolica and Q. dentate was 0.053. The Japanese emperor oak and Mongolian oak populations formed separate clusters in an UPGMA dendrogram. Taking into account morphological and ecological isolation of the species, we suggest that the differences in gene frequencies may reflect selection acting in favor of adaptation to different growth conditions and counteracting between-species hybridization.     

干旱和湿润生境下辽东栎群体遗传结构及其适应意义的初步研究

应用同工酶分析方法,测定北京市东灵山区两个分别代表干旱和湿润生境的辽东栋（ＱｕｅｒｃｕｓｌｉａｏｔｕｎｇｅｎｓｉｓＫｏｉｚ．）群体的遗传结构。共分析统计了１３ 个酶系统３０ 个位点。结果表明：辽东栎群体内部存在丰富的遗传变异（多态位点百分率为８６．６％ ,等位基因平均数为２．２５）。两群体遗传结构的相似性程度很高（Ｄ＝ ０．０２９, ＧＳＴ＝ ０．０４８）;但在个别位点上仍存在较大差异,这些差异的产生可能与对小生境的适应有关。对不同年龄段的初步分析结果显示,基因频率的动态变化可能有其适应意义     

Variation in morphological traits in a recent hybrid zone between closely related Quercus liaotungensis and Q. mongolica (Fagaceae)

Aims Hybridization usually leads to gene introgression between related species in hybrid zones, associated with complex patterns of morphological variation. Nevertheless, previous studies have tended to ignore the effects of geographic variation in hybridization rates on species taxonomy. This study aims to investigate the variation of morphological traits between two sympatric and taxonomically confused oak species, Quercus liaotungensis and Q. mongolica, and reveal the effects of hybridization rates on morphological traits and the taxonomic boundary.Methods We used seven microsatellite loci to evaluate species status and measured 15 morphological traits in 26 trees in the recent hybrid zone between Q. liaotungensis and Q. mongolica, and we characterized the differences between the two oak species and their hybrids for the investigated traits.Important findings Molecular analyses indicated that 74% of 78 sampled maternal trees were hybrids between Q. liaotungensis and Q. mongolica although the observed morphological variation suggested that they had remained distinct species. Across all of the differentiated leaf and reproductive traits, the hybrids expressed patterns similar to Q. liaotungensis, which may suggest dominant expression of parental characters. These results are consistent with our expectation that hybrids will be difficult to distinguish from parental species in a recent hybrid zone.     

应用ISSR-PCR分析蒙古栎种群的遗传多样性

本研究应用ISSR标记技术对东北地区的优势树种蒙古栎(Quercus mongolica)的25个种群遗传多样性进行了分析, 目的是为蒙古栎早期选择提供依据。从60条ISSR引物中筛选出10个特异性强、稳定性好的引物进行ISSR分析。共获得位点数71个, 其中多态位点数56个, 多态位点百分率为78.87%。PopGene分析结果表明: 种群的平均多态位点百分率为45.2%, Shannon表型多样性指数(I)平均值为0.25, 具有较高的遗传多样性, 种群间存在一定程度的基因流(N_m为1.3818)和遗传分化(Nei’s信息多样性指数平均值为0.1068, G_st平均值为0.2657), 种群内的基因多样度占总种群的73.43%, 种群间占26.57%, 表明蒙古栎种群的变异主要来源于种群内。结合聚类分析和地理变异规律把种群划分为两个大的种群组: 小兴安岭种群组和长白山种群组。以上结果可为栎属种质资源的保护和利用以及物种分化研究提供基础资料。     

Species distinction in Irish populations of Quercus petraea and Q. robur: morphological versus molecular analyses

BACKGROUND AND AIMS: Populations of oak (Quercus petraea and Q. robur) were investigated using morphological and molecular (AFLP) analyses to assess species distinction. The study aimed to describe species distinction in Irish oak populations and to situate this in a European context. METHODS: Populations were sampled from across the range of the island of Ireland. Leaf morphological characters were analysed through clustering and ordination methods. Putative neutral molecular markers (AFLPs) were used to analyse the molecular variation. Cluster and ordination analyses were also performed on the AFLP markers in addition to calculations of genetic diversity and F-statisitcs. KEY RESULTS: A notable divergence was uncovered between the morphological and molecular analyses. The morphological analysis clearly differentiated individuals into their respective species, whereas the molecular analysis did not. Twenty species-specific AFLP markers were observed from 123 plants in 24 populations but none of these was species-diagnostic. Principal Coordinate Analysis of the AFLP data revealed a clustering, across the first two axes, of individuals according to population rather than according to species. High F(ST) values calculated from AFLP markers also indicated population differentiation (F(ST) = 0.271). Species differentiation accounted for only 13 % of the variation in diversity compared with population differentiation, which accounted for 27 %. CONCLUSIONS: The results show that neutral molecular variation is partitioned more strongly between populations than between species. Although this could indicate that the populations of Q. petraea and Q. robur studied may not be distinct species at a molecular level, it is proposed that the difficulty in distinguishing the species in Irish oak populations using AFLP markers is due to population differentiation masking species differences. This could result from non-random mating in small, fragmented woodland populations. Hybridization and introgression between the species could also have a significant role.     

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.     

Effect of a red oak species gradient on genetic structure and diversity of Quercus castanea (Fagaceae) in Mexico

Incipient reproductive barriers are a common characteristic of oak species. Disruption of these barriers promotes changes in diversity and genetic structure of the species involved. Quercus castanea is a red oak with wide geographic distribution in Mexico, which presents atypically high morphological variability when it occurs in sympatry with other red oak species, suggesting that hybridization may explain the observed variation. We tested if the genetic structure and diversity levels of Q. castanea are related to the number of red oak species growing in sympatry. In total, 14 microsatellite (SSRs) primers (six nSSRs and eight cpSSRs) were used in 120 Q. castanea individuals (20/site) belonging to six populations, where the number of red oak species associated varied from zero to five. Results showed a positive and significant relationship between the genetic diversity of Q. castanea and the number of red oak species growing in sympatry, regardless of the marker type or the parameter of genetic diversity analyzed. Also, we found a higher genetic differentiation of Q. castanea populations using cpSSRs in comparison with nSSRs. Our results suggest that temperate forests with high red oaks species richness co-dominated by Q. castanea promote the increase in this species genetic diversity. From a conservation perspective, high genetic diversity levels of foundation species such as Q. castanea may have positive cascade effects extending to other species in the community.     

Conservation genetics of rare trees restricted to subtropical montane cloud forests in southern China: a case study from <Emphasis Type="Italic">Quercus arbutifolia</Emphasis> (Fagaceae)

Montane cloud forests (MCFs), with their isolated nature, offer excellent opportunities to study the long-term effects of habitat fragmentation and the impacts of climate change. Quercus arbutifolia is a rare oak in MCFs of southern China and Vietnam. Its isolated populations, small population size and unique ecological niche make this species vulnerable to climate change and habitat loss. In this study, we used chloroplast (cpDNA) and nuclear (ITS) DNA sequences to investigate genetic divergence patterns and demographic history of five of the six known populations of Q. arbutifolia. Considering its small population size and fragmentation, Q. arbutifolia has unexpectedly high genetic diversity. The time since the most recent common ancestor of all cpDNA haplotypes was c. 10.25 Ma, and the rapid diversification of haplotypes occurred during the Quaternary. The maximum clade credibility chronogram of cpDNA haplotypes suggests that the DM population (Daming Mountain, Guangxi province) diverged early and rapidly became isolated from other populations. The Pearl River drainage system may have been the main geographic barrier between DM and other populations since the late Miocene. ITS data suggests that population expansion occurred during the last interglacial of the Quaternary. The combined effects of pre-Quaternary and Quaternary climatic and geological changes were the main drivers to the current genetic diversity and distribution pattern of Q. arbutifolia. Because of the high between-population genetic differentiation and high within-population genetic diversity of Q. arbutifolia, conservation efforts should be implemented for all populations, but if conservation resources are limited, populations DM, YZ (Mang Mountain, Hunan province) and ZZ (Daqin Mountain, Fujian province) should have priority.     

AFLP markers demonstrate local genetic differentiation between two indigenous oak species [ Quercus robur L. and Quercus petraea (Matt.) Liebl.] in Flemish populations

The nuclear genetic variation within and between four sessile ( Q. petraea) and six pedunculate ( Q. robur) autochthonous Flemish oak populations was investigated with AFLP markers. One sessile and one pedunculate oak population were additionally screened for detailed leaf characteristics using an image analysis system. Principal coordinate analysis on the AFLP data classified the oaks in two main groups, according to their taxonomic status. No species-specific AFLP markers were found using four primer combinations, but marker frequency differences up to 71% were recorded between both species. Analysis of the genetic structure showed that the divergence between species, as observed by ordination, was significant. Both species revealed similar diversity levels. A smaller though significant differentiation was also revealed for both species among populations within species. Molecular and morphology based approaches showed a high degree of consistency. Screening of 60 AFLP primer combinations using a bulking strategy did not allow identifying species-specific markers, which supports the conclusions reached in previous studies. The distribution of genetic variability at the species and at the population level is discussed.     

北京东灵山地区不同海拔柴胡居群的遗传多样性

利用ISSR技术对北京东灵山地区不同海拔的6个柴胡居群进行分析,观察不同海拔柴胡居群的遗传多样性。结果表明,东灵山地区不同海拔柴胡居群的遗传多样性差异较大,海拔1135m居群表现出较高的遗传变异水平,高海拔居群遗传多样性较低;遗传距离与海拔差距有一定的相关性,相邻海拔的不同柴胡居群间具有相对较低的遗传距离;柴胡具有较强的遗传分化趋势,且大部分变异存在于居群内。不同海拔导致的异质生境及基因流是影响柴胡居群遗传多样性的主要原因。     

Allozyme variation in cork oak (Quercus suber L.): the role of phylogeography and genetic introgression by other Mediterranean oak species and human activities

 Genetic variation in the cork oak (Quercus suber L.) was investigated using 11 loci from seven enzyme systems in 40 populations sampled over the entire distribution of this species in the western Mediterranean Basin. Mean heterozygosity values over the polymorphic loci (Ho=0.283), the percentage of polymorphic populations (M=0.76), and the total genetic diversity (Ht=0.31) from which 11% was accounted for among-population variation, are among the highest recorded in oak species. In contrast to previous results in holm oak (Q. ilex L.), another evergreen species in the same area, cork oak possessed a smaller allele pool and a lower average number of alleles per locus and per population (A=2.0). More particularly, very few low-frequency alleles were observed in cork oak except for eight populations in which allozyme polymorphism at locus Pgi 1, diagnostic between both species, indicates that these low-frequency alleles are introgressed from holm oak. On the basis of the genetic distance estimated from allozyme frequencies, 32 of the 40 cork oak populations studied were classified into two very distinct sets which also corresponded to distinct geographic areas. One set gathered together the 18 populations from the Iberian peninsula and two adjacent areas in France, i.e. the centre of origin of cork oak, according to paleobotanical data. This set was characterized by a larger allele pool, a higher within-population genetic diversity and a lower differentiation between populations than was observed in the other set, which comprised the populations from North Africa, Sicily, Sardinia, Corsica, continental Italy and the region of Provence (southeastern France). In these more southern and eastern disjunct areas, cork oak migration from Iberia may have occurred at different periods since the end of the Tertiary. The possible effect of human activity on cork oak genetic structure, i.e. the selection of good-quality cork, acorn over-use for animal food, and even human nutrition, is discussed. Received: 3 March 1998 / Accepted: 19 March 1998     

Variability of allozyme and cpSSR markers in the populations of Siberian spruce

The variability of 21 allozyme and three microsatellite loci of chloroplast DNA (cpDNA) was studied in the populations of Siberian spruce (Picea obovata Ledeb.) from Irkutsk oblast, Magadan oblast, Buryatia, and Mongolia. It was demonstrated that the highest level of genetic diversity among the examined populations at both allozyme and microsatellite loci was observed in the Tulyushka population from Irkutsk oblast. The lowest level of genetic diversity was observed in marginal isolated populations of Bogd Uul and Magadan. In the relict spruce population from Olkhon Island, differing from the other populations in the lowest allelic diversity of both types of markers, no expected decline of expected heterozygosity and haplotype diversity was observed. In this population, the variability parameters mentioned were close to the population mean. The obtained intrapopulation and intraspecific variability parameters of allozyme and microsatellite loci of chloroplast DNA and the data on the population differentiation at these loci indicate that the given markers can be used for the analysis of the population structure of Siberian spruce.     

子午岭三种生境下辽东栎幼苗定居限制

辽东栎(Quercus wutaishanica)是子午岭地区的乡土乔木树种,也是该地区气候顶极群落的建群种,其幼苗的补充更新影响着森林群落的结构及物种组成。在3种典型生境(辽东栎林、人工油松林、灌草丛)中,设置3因素(种子、干扰、遮荫)两水平的野外播种实验(随机区组设计),记录辽东栎幼苗出苗量,并监测幼苗同生群在3种生境中3a间的生长状况,以确定种子及微生境在辽东栎幼苗补充过程中的限制作用。播种实验样方大小30cm×30cm,共计216个样方。结果显示,在辽东栎林及油松林内,增加种子和干扰强度(去除枯落物),能引起出苗量和幼苗补充量的显著增加,且2种处理方式间存在交互作用,表明在郁闭林冠下,辽东栎幼苗的补充受到了种子和微生境的双重限制,枯落物是导致微生境限制的主要因素之一。在灌草丛生境,各种处理方式均不能增加幼苗的补充量,表明辽东栎无法在开阔生境(强光照、干旱)中完成实生幼苗的补充更新。3种生境中的幼苗同生群生存分析表明,辽东栎幼苗在森林群落中存活率显著高于灌草丛群落。根据幼苗生长指标判断,在3种生境中,人工油松林是辽东栎幼苗定居的最佳场所。与实验预期相反,灌木对辽东栎幼苗的补充无显著影响。     

Limited hybridization between Quercus lobata and Quercus douglasii (Fagaceae) in a mixed stand in central coastal California

Many oak species are interfertile, and morphological and genetic evidence for hybridization is widespread. Here we use DNA microsatellite markers to characterize hybridization between two closely related oak species in a mixed stand in central coastal California, Quercus lobata (valley oak) and Q. douglasii (blue oak) (Fagaceae). Genotypes from four microsatellite loci indicate that many alleles are shared between the two species. However, each species harbors unique alleles, and allele frequencies differ significantly. A Bayesian analysis of genetic structure in the stand identified two highly differentiated genetic clusters, essentially corresponding to species assignment based on morphology. Data from the four loci were sufficient to assign all 135 trees to one of the two species. In addition, five putative hybrid individuals having intermediate morphologies could be assigned genetically to one or the other species, and all but one had low probability of hybrid ancestry. Overally, only six (4.6%) trees showed >0.05 probability of hybrid ancestry, in all cases their probabilities for nonhybrid ancestry were substantially higher. We conclude that adult hybrids of Q. douglasii × Q. lobata are rare at this site and plasticity in morphological characters may lead to overestimates of hybridization among Quercus species.     

中国特有种四合木种群遗传多样性的RAPD分析

采用随机扩增多态性 DNA(RAPD)技术检测了西鄂尔多斯高原特有种四合木种群 5个斑块的遗传多样性。2 2个扩增引物产生 1 1 6条带 ,Shannon信息指数和 Nei指数对 RAPD数据的分析表明 :四合木种群存在较高的遗传多样性 ,其中千里山斑块的遗传多样性和多态位点比例较高 ,石嘴山斑块的最低。遗传多样性的 86.5 %存在于斑块内 ,斑块间的遗传变异为 1 3 .5 %。遗传距离与地理距离无直接相关关系。这些结果说明 ,遗传多样性反映了四合木种群基因组 DNA存在较高的变异性 ;同时各斑块间存在一定的基因流 ,四合木各斑块可看成是处于同一种群的半隔离状态 (meta-种群 ) ,对四合木应注意保护遗传多样性丰富的 meta-种群。     

Population genetic structure in the dioecious pioneer plant species Hippophae rhamnoides investigated by random amplified polymorphic DNA (RAPD) markers

Hippophae rhamnoides is an outcrossing pioneer plant species with a severely fragmented distribution. Random amplified polymorphic DNA (RAPD) marker variation was analysed in 10 populations of ssp. rhamnoides and in one population of ssp. mongolica to estimate the amount and distribution of genetic variability. No less than 89.7% of the scorable markers were polymorphic, but few of these were fixed and populations consequently differed mainly by frequency variation of individual markers. Within-population gene diversity was somewhat low for an outcrossing plant species: 0.192 or 0.159 for ssp. rhamnoides , depending on whether it was based on all 156 polymorphic RAPDs or on only those 63 RAPDs that fulfilled the 3/ N criterion. Analysis of molecular variance applied to the ssp. rhamnoides showed only 15% between-population variability, indicating a relatively restricted population differentiation as expected in outcrossing species and shown in several other AMOVA studies. The tendency for island populations to be somewhat more differentiated, and to have less within-population diversity than mainland populations, may indicate an effect of population fragmentation. Genetic distance estimates among populations, obtained with and without pruning of RAPD loci on the basis of the 3/ N criterion, were generally in very good agreement. Cluster analyses and principal coordinate analyses showed populations of ssp. rhamnoides to be rather close, but quite isolated from the single ssp. mongolica population. Genetic and geographical distances between the ssp. rhamnoides populations were not associated, indicating that large-scale geographical and ecotypic differentiation was not reflected in the RAPD profiles.     

The clonal structure of Quercus geminata revealed by conserved microsatellite loci

The scrub oak communities of the southeastern USA may have existed at their present locations for thousands of years. These oaks form suckers, and excavations of root systems suggest that clones may occupy very large areas. Resolution of the clonal nature of scrub oaks is important both to manage the tracts of this ecosystem that remain, and in conducting long-term ecological studies, where the study area must substantially exceed the area occupied by any single clone. Microsatellites were used to determine the genetic diversity of a dominant oak species within a 2-ha long-term experimental site on Merritt Island at the Kennedy Space Center. This area contains a long-term study of the effects of elevated CO2 on the ecosystem. Conservation of seven microsatellite loci, previously identified in the sessile oak, Quercus petraea, was tested in two Florida scrub oak species, Q. geminata and Q. myrtifolia. Sequence analysis revealed that all seven microsatellite loci were conserved in Q. geminata and five loci were conserved in Q. myrtifolia. Six microsatellite loci were polymorphic in Q. geminata and these were subsequently used to investigate the clonal structure of the Q. geminata population. Twenty-one unique combinations of microsatellites, or haplotypes, occurred only once, whereas the remaining 26 individuals belonged to a total of seven different haplotypes. Trees with identical haplotypes were in close proximity, supporting the interpretation that they were clones. The results showed that there is significant genetic diversity within the 2-ha experimental site. Microsatellites provided a powerful and noninvasive tool for distinguishing individual genotypes and determining an adequate area for long-term ecosystem studies.