匍匐茎草本植物蛇莓小尺度克隆结构

采用ISSR分子标记技术比较分析了3个斑块匍匐茎草本植物蛇莓的遗传多样性、克隆多样性和克隆结构,探讨蛇莓克隆结构的形成机制及与环境的相关性.结果表明蛇莓的遗传多样性较低,多态位点百分率P为37.93%, Shannon信息指数I为0.2402, Nei指数h为0.1677;蛇莓的克隆多样性与其它克隆植物较为接近,基因型比率G/N=0.2013,Simpson多样性指数D为0.6396,基因型分布的均匀度E为0.5862;蛇莓的遗传变异大部分存在于斑块间,基因流较小,仅为0.1019.3个斑块蛇莓的遗传多样性以临海斑块(LH)最高(P=10.34%, I =0.0513, h =0.0344),安吉斑块(AJ)次之(P=10.34%, I =0.0443, h =0.027),而天台斑块(TT)最低(P=5.17%, I =0.0325, h =0.0227).基株数目、基因型比率、Simpson多样性指数和基因型分布的均匀度均表明克隆多样性以LH斑块最大(G=12, G/N=0.3077, D=0.8677, E=0.8380),AJ斑块次之(G=9, G/N=0.1800, D=0.5870, E=0.4753),TT斑块最低(G=5, G/N=0.1163, D=0.4642, E=0.4453).3个斑块中均存在优势克隆,但优势克隆的大小在3个斑块中均不相同,以LH斑块最小,AJ斑块次之,TT斑块最大.空间自相关分析显示LH斑块在20 cm和40 cm时存在显著性正相关,其X轴截矩为49.959;AJ斑块仅在20 cm时存在显著性正相关,其X轴截矩为63.333;TT斑块在20 cm、30 cm、40 cm和70 cm时均存在显著性正相关,其X-轴截矩高达90.512.这表明3个不同斑块内蛇莓基因型的空间分布距离不同,TT斑块最大,AJ斑块最小;克隆所能到达的距离也不同,TT斑块最大,LH斑块最小.3个不同斑块蛇莓的遗传多样性、克隆多样性与克隆结构具有明显的差异.蛇莓的遗传多样性与克隆多样性与蛇莓较强的克隆繁殖能力和较低的种子萌发率有关.蛇莓的遗传结构、克隆结构及克隆的空间分布格局与不同斑块所处生境的生态因子及其它因素(如干扰、演替和突变)有关.     

不同年龄巴山木竹种群克隆结构

很多竹类植物是典型的克隆植物,也是大熊猫的食物。研究典型竹子种群克隆结构的形成和发展对竹林的生产和抚育具有理论和实践意义,可为预测该竹林群落的演替趋势和大熊猫保护提供科学依据。利用SSR标记研究不同年龄A(7龄)、B(30龄)和C(60龄)巴山木竹种群的克隆结构和多样性,探讨小尺度范围内不同年龄巴山木竹种群的克隆结构及斑块的建立和发展。8对SSR引物共扩增出了118个位点,3个种群样地的256个样本共检测到了49个克隆(基因型),A、B和C种群分别检测出31、10个和8个克隆。随着种群年龄的增长,巴山木竹克隆面积增加,克隆数量减少;A和B样地各克隆分布格局为团块状,而C样地克隆既有团块状又有离散状。这一结果显示出在幼苗定居的初期,基株可能以短距离的克隆延伸为主从而呈现出团块状;而随着年龄的增长,克隆面积不断扩大,当复轴混生型的巴山木竹克隆受到强大的压迫时,基株可能会进行较多的单轴和长距离克隆延伸,呈现出离散状。Mantel检测和空间自相关分析都支持3个样地在小尺度范围内存在明显的克隆空间遗传结构。3个样地在10 m等级下显著的正相关空间遗传结构距离为3.1、28、48 m,X-轴截距为9.051、30.698和50.536,空间自相关系数的范围分别为0.1—0.167、0.008—0.703和0.006—0.735。由此可推断,随着年龄的增长,巴山木竹克隆斑块的规模在不断地扩大,同一克隆的分株数量增加,在均匀取样情况下,正相关空间遗传结构距离范围内取到具有相同基因型的可能性越大。A、B和C 3样地的基因型比率(G/N)为1、0.14和0.055,Simpson多样性指数(D)分别为1、0.876和0.744。这说明巴山木竹幼苗期基因型比例远远高于成年的竹林,随着年龄的增长巴山木竹克隆多样性虽有所降低,但由于有性繁殖的作用仍然保持了较高的多样性。聚类和主坐标分析均表明总体上各样地的克隆被聚为一类,但不同样地少数克隆的基因型有重叠和聚集,可推断出不同巴山木竹种群之间可能存在着基因流动和近似的克隆起源。     

浙江天台山甜槠种群遗传结构的空间自相关分析

采用空间自相关分析方法对浙江天台山亚热带常绿阔叶林优势种甜槠种群全部个体及不同年龄级个体的小尺度空间遗传结构进行了分析,以探讨甜槠种群内遗传变异的分布特征及其形成机制。根据11个ISSR引物所提供的多态位点,经GenAlEx 6软件计算地理坐标和遗传距离矩阵在10个距离等级下的空间自相关系数。在样地内,甜槠种群内个体在空间距离小于10 m时存在显著的正空间遗传结构,其X-轴截矩为9.945。甜槠种群的空间遗传结构与其种子短距离传播和广泛的花粉传播有关。Ⅰ年龄级、Ⅱ年龄级和III年龄级个体在空间距离小于10 m时存在显著的正空间遗传结构,其X-轴截矩分别为11.820、9.746和9.792。当距离等级为5 m时,其空间自相关系数r分别为0.068、0.054和0.070。Ⅳ年龄级个体在所有空间距离等级中均不存在显著的空间遗传结构。甜槠是多年生、长寿命植物,自疏作用是导致IV年龄级个体空间遗传结构消失的主要原因。     

野生地椒的斑块多样性及空间结构

将ISSR、SRAP分子标记与空间自相关分析技术相结合,对我国野生百里香属植物分布最南端 的怀远3个地椒居群进行了以斑块为单位的遗传多样性、克隆多样性和克隆结构、空间结构的研究.结果表明：地椒野生居群内不同斑块间存在较高的遗传多样性和克隆多样性,多样性条带百分率为75.75％,Nei基因多样性指数为0.2537, Shannon信息多样性指数为0.3811,基因型比率平均为0.61,Simpson指数平均为0.96,Fager均匀性指数平均为0.91.居群间的遗传分化较低,在总的遗传多样性中,90.35%来自居群内斑块间的变异,居群间占9.65％.野生地椒居群间无共有基因型斑块,居群内不同斑块间在一定范围内具有镶嵌性,克隆斑块间的分布范围主要集中在0～25 m.该地区地椒居群除了在部分位点呈现一定相关性外,总体缺乏空间结构.该地区野生地椒种群斑块的建立应为种子入侵所致,其后克隆繁殖对斑块的发展及种群的扩张起到了主要作用.     

论克隆植物的遗传多样性

概述了克隆植物的类型与特点 ,对克隆植物的遗传多样性及其遗传结构的一些特点进行了综述 ,并讨论了克隆植物遗传变异的来源。总体而言 ,克隆植物拥有比早期推测大得多的遗传变异 ,虽然克隆种与其近缘有性繁殖种相比 ,遗传多样性较低 ,但广泛的遗传单态性却很罕见。克隆植物种群的遗传结构有所改变 ,广布基因型很少 ,大多数基因型仅分布于某一种群之内 ,种群间基因型多态性存在广泛的变异。不同克隆植物之间遗传多样性相差很大 ,遗传结构也有巨大差异。说明除生殖模式外 ,其他的一些因素 ,如地理分布范围、生境特点 ,散布方式和种群历史等都对克隆植物遗传多样性有重要影响。     

论克隆植物的遗传多样性

概述了克隆植物的类型与特点,对克隆植物的遗传多样性及其遗传结构的一些 特点进行了综述,并讨论了克隆植物遗传变异的来源。总体而言,克隆植物拥有比早期推测大得多的遗传变异,虽然克隆种与其近缘有性繁殖种相比,遗传多样性较低,但广泛的遗传单态性却很罕见。克隆植物种群的遗传结构有所改变,广布基因型很少,大多数基因型仅分布于某一种群之内,种群间基因型多态性存在广泛的变异。不同克隆植物之间遗传多样性相差很大,遗传结构也有巨大差异。说明除生殖模式外,其他的一些因素,如地理分布范围、生境特点,散布方式和种群历史等都对克隆植物遗传多样性有重要影响。     

土壤养分斑块对比度改变活血丹克隆整合强度和方向

克隆植物相连片段(或分株)常常生长在不同的土壤养分斑块中。克隆整合使得生长在异质养分斑块中的克隆片段(或分株)产生局部和非局部反应,从而影响相连片段(或分株)的表型可塑性。为了揭示养分斑块对比度对活血丹(Glechoma longituba)克隆整合的影响,在一控制实验中,将活血丹克隆片断种植于4种不同对比度的环境中,即:无对比度(对照)、低对比度、中对比度和高对比度。活血丹在气体交换、水势、荧光、形态、生长与分配方面的克隆整合强度随养分斑块对比度的增强而表现出增强或减弱的变化趋势;养分斑块对比度越强,活血丹气体交换和荧光暗反应的整合强度越小,叶片水势整合强度越大。斑块对比度可改变部分性状的克隆整合方向;超过一定的对比阈值,整合强度随养分对比度的变化趋势会向着相反方向转变。克隆整合对生理特征的修饰幅度小于对生长特征的修饰幅度。这些结果指示:养分斑块对比度可通过修饰克隆整合格局(即强度和方向)而改变克隆植物的表型可塑性。     

佛坪国家级自然保护区秦岭箭竹克隆结构的SSR分析

利用SSR分子标记技术分析了佛坪国家级自然保护区秦岭箭竹(Fargesia qinlingensis)的克隆多样性和克隆结构,以探讨小尺度范围内秦岭箭竹自然居群遗传变异的分布特征,对该种开花特性、高山地区生态环境维护和大熊猫的保护提供重要依据。结果表明7对SSR引物共扩增出79个位点,其中多态性位点77个,多态位点百分率(PPB)为97.47%。秦岭箭竹的142个分株共形成107个克隆,最大克隆可达5 m。克隆多样性略高于其他克隆植物的平均值(D=0.62,G/N=0.17,E=0.68),基因型比率(G/N)、Simpson指数(D)、平均克隆大小(N/G)和Fager均匀性指数(E)分别为0.7535、0.9680、1.3271和0.5109。克隆空间结构分析表明秦岭箭竹的克隆构型为密集型,各克隆呈镶嵌性分布,同一克隆的分株排列紧密。克隆聚类分析表明各克隆之间聚类不明显,总体上来自同一样地的克隆被聚为一类。空间自相关分析显示在空间距离为36 m范围内,分株比基株有更显著的空间遗传结构,空间自相关系数r的取值范围分别为0.084—0.626和0.024—0.288,说明克隆繁殖在一定程度上限制了空间遗传结构的范围。样地内秦岭箭竹个体在空间距离小于44 m时存在显著的正相关空间结构,特别是在4 m处表现出最大的空间自相关系数(r=0.626),表明空间距离相距4 m内的个体最有可能属于同一克隆,4 m比5 m更能表现出清晰的克隆结构,X-轴截距为52.280,代表了秦岭箭竹不规则克隆的平均最小长度。秦岭箭竹的克隆多样性和克隆结构与初始苗补充、花粉散播方式和微环境差异有关。     

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。     

具混合繁殖策略的草本植物异果舞花姜的居群遗传结构

 居群遗传结构的形成受到各种因素的影响。其中, 繁殖方式可能对居群内遗传变异有极其重要的意义, 而距离隔离也是居群间变异产 生的主要原因之一。异果舞花姜(Globba racemosa)具有混合繁殖策略(以种子进行有性繁殖和以珠芽进行无性克隆繁殖)。调查分布于云南的7 个异果舞花姜居群间有性与无性克隆繁殖的差异。采用ISSR标记研究各个居群的遗传多样性与克隆多样性, 探讨繁殖方式和距离隔离对居群遗 传结构的影响。调查结果表明, 异果舞花姜各个居群存在一定的繁殖差异。ISSR结果显示, 该种在种水平上呈现较高水平的遗传变异 (PPB=71.19%), 大部分的变异来自于居群间(G_ST = 0.590 7)。同时, 异果舞花姜具有较高水平克隆多样性(G/N = 0.88)。遗传多样性和克隆多 样性与繁殖水平的变异间相关性不明显, 说明繁殖方式不是居群遗传结构形成的必要和决定性的因素。居群间的地理距离与遗传距离显著相关 (r = 0.68, p < 0.05), 表明距离隔离是居群间遗传变异形成的重要原因。其它因素(如少量新有性个体的补充、细胞突变、奠基效应等)也对 异果舞花姜居群遗传结构的形成和维持起到了重要作用。     

Fine-scale clonal structure and diversity of invasive plant Mikania micrantha H.B.K. and its plant parasite Cuscuta campestris Yunker

The fine-scale clonal structure in the patch of the invasive plant Mikania micrantha H.B.K. and its plant parasite Cuscuta campestris Yunker were investigated by distinguishing genets using ISSR markers. A high level of clonal diversity (G/N = 0.7, D = 0.9579, E = 0.7778) in M. micrantha and a low level of clonal diversity (G/N = 0.2, D = 0.7632, E = 0.9479) in C. campestris might be due to the different reproductive strategies, different migration rates and different number of founder. Clonal composition of M. micrantha (14 genets of 20 ramets) and C. campestris (4 genets of 20 ramets) were significantly different. There was no relationship between host and parasite genetic distance matrices using Mantel test (r = 0.073, P = 0.150). Spatial autocorrelation analysis of M. micrantha showed that the correlation value was positive and significant at 2 m with an x-intercept of 3.5 and 4.0 m for distance class sizes of 1 and 2 m, respectively. Spatial autocorrelation analysis of C. campestris showed that the correlation value was positive and significant at 2 m and significantly negative at 10 m with an x-intercept of 4.8 and 6.6 m for distance class sizes of 1 and 2 m, respectively.     

Clonal and genetic structure of two Mexican oaks: Quercus eduardii and Quercus potosina (Fagaceae)

Quercus eduardii and Q. potosina are dominant oak species in Sierra Fría, Aguascalientes, Mexico. These species have been exploited for multiple purposes since the 16th century. Both species produce clonal offspring through root suckering and acorns through sexual reproduction. To understand clonality for the implementation of the most adequate actions for the conservation of these species, we addressed the following questions: (a) what is the spatial clonal structure of both species? (b) How much clonal and genetic diversity is maintained in these species? Random Amplified Polymorphic DNAs (RAPDs) were used as molecular markers for these analyses. Genets of both species have few ramets and these grow close the parent tree. Autocorrelation analyses at the ramet level showed an aggregated distribution at short distances and a random spatial distribution at larger distances. Also, at the genet level the autocorrelation analyses showed a random distribution. Clonal diversity was high in both species (Q. eduardii: D=0.963, G/N=0.60; Q. potosina: D=0.985, G/N=0.65). Genetic diversity was high within populations (Q. eduardii: H _e =0.33±0.11; Q. potosina: H _e =0.35±0.11). Low levels of genetic differentiation among populations were observed (Q. eduardii ? _st =0.19, P < 0.002; Q. potosina ? _st =0.13, P < 0.002). Both species maintain high levels of clonal and genetic diversity, probably due to successful sexual reproduction, which allows gene flow among populations. Conservation and/or reforestation programs must include seed collections and germplasm banks. Due to the small genet size and the high clonal diversity of these species, seeds can be collected in any place in Sierra Fría, Aguascalientes.     

Clonal and fine-scale genetic structure in populations of a restricted Korean endemic, Hosta jonesii (Liliaceae) and the implications for conservation

BACKGROUND AND AIMS: In plant populations the magnitude of spatial genetic structure of apparent individuals (including clonal ramets) can be different from that of sexual individuals (genets). Thus, distinguishing the effects of clonal versus sexual individuals in population genetic analyses could provide important insights for evolutionary biology and conservation. To investigate the effects of clonal spread on the fine-scale spatial genetic structure within plant populations, Hosta jonesii (Liliaceae), an endemic species to Korea, was chosen as a study species. METHODS: Using allozymes as genetic markers, spatial autocorrelation analysis of ramets and of genets was conducted to quantify the spatial scale of clonal spread and genotype distribution in two populations of H. jonesii. KEY RESULTS: Join-count statistics revealed that most clones are significantly aggregated at < 3-m interplant distance. Spatial autocorrelation analysis of all individuals resulted in significantly higher Moran's I values at 0-3-m interplant distance than analyses of population samples in which clones were excluded. However, significant fine-scale genetic structure was still observed when clones were excluded. CONCLUSIONS: These results suggest that clones enhance the magnitude of spatial autocorrelation due to localized clonal spread. The significant fine-scale genetic structure detected in samples excluding clones is consistent with the biological and ecological traits exhibited by H. jonesii including bee pollination and limited seed dispersal. For conservation purposes, genetic diversity would be maximized in local populations of H. jonesii by collecting or preserving individuals that are spaced at least 5 m apart.     

Ecological genetic interactions between a clonal host plant (Spartina pectinata) and associated rust fungi Puccinia seymouriana and Puccinia sparganioides

The spatial scale of genetic diversity among patches of a host plant could affect the likelihood of pathogen adaptation to the host. If host patches are genetically distinct, pathogen adaptation to local host genotypes may occur. To study this issue, we focused on the ecological and genetic interactions between two rust fungi, Puccinia seymouriana and P. sparganioides, and the clonal prairie grass, Spartina pectinata. In a field transplant experiment, disease levels differed among plants from different patches, suggesting variation in resistance. Over a 4.5-km scale, disease levels were not higher on plants transplanted back into their source patch as opposed to other locations, providing no evidence for local adaptation in the pathogen. However, on the spatial scales examined (ranging from 0.2 km to 120 km), there was no relationship between the physical distance separating host patches and their similarity in isozyme banding patterns, implying that plants from more distant patches are not necessarily more genetically distinct than plants from nearby patches. Plants derived from the most distant location had, on average, the lowest mean number of pustules at the end of the summer, suggesting the need for reciprocal transplant studies to be performed on a larger spatial scale.     

Plasticity in R/S ratio, morphology and fitness-related traits in response to reciprocal patchiness of light and nutrients in the stoloniferous herb, Glechoma longituba L

Clonal fragments of the stoloniferous herb Glechoma longituba were subjected to a complementary patchiness of light and soil nutrients including two spatially homogeneous treatments (SR–SR and IP–IP) and two spatially heterogeneous treatments (IP–SR and SR–IP). SR and IP indicate patches (shaded, rich) with low light intensity (shaded, S), high nutrient availability (rich, R) and patches (illuminated, poor) with high light intensity (illuminated, I) and low nutrient availability (poor, P), respectively. Plasticity of the species in root–shoot ratio, fitness-related traits (biomass, number of ramets and dry weight per ramet) and clonal morphological traits (length and specific length of stolon internodes, area and specific area of laminae, length and specific length of petioles) were experimentally examined. The aim is to understand adaptation of G. longituba to the environment with reciprocal patches of light and soil nutrients by plasticities both in root–shoot ratio and in (clonal) morphology. Our experiment revealed performance of the clonal fragments growing from patches with high light intensity and low soil nutrient availability into the adjacent opposite patches was increased in terms of the fitness-related characters. R/S ratio and clonal morphology were plastic. Meanwhile, the capture of light resource from the light-rich patches was enhanced while the capture of soil nutrients from either the nutrient-rich or the nutrient-poor patches was not. Analysis of cost and benefit disclosed positive effects of clonal integration on biomass production of ramets in the patches with low light intensity and high soil nutrient availability. These results suggest an existence of reciprocal translocation of assimilates and nutrients between the interconnected ramets. The reinforced performance of the clonal fragments seems to be related with specialization of clonal morphology in the species.     

Clonal and spatial genetic structure in natural populations of Luohanguo (Siraitia grosvenorii), an economic species endemic to South China,as revealed by RAPD markers

Clonal growth is generally expected to have significant effects on the spatial genetic structure within populations. In this study, random amplified polymorphic DNA (RAPD) markers were used to reveal clonal and spatial genetic structure of four natural populations of Luohanguo (Siraitia grosvenorii), an economic vine species endemic to South China. A total of 351 ramets were assigned to 76 distinct multi-locus genotypes (i.e. genets), with the G/N varying from 0.121 to 0.350. No widespread genet was found across different populations. The clonal diversity (D) and evenness (E) ranged from 0.333 to 0.828 and from 0 to 0.741, respectively. While most genets consisted of fewer than five ramets, we observed some dominant genets that had much more (up to 69) ramets and spread over large areas. Spatial autocorrelation analyses revealed a spatial genetic structure (i.e. significant positive autocorrelation within 20 m and negative autocorrelation beyond 40 m) in one population, but not in other three populations with smaller population size. This study highlights the importance of clonal growth in shaping the spatial genetic structure in Luohanguo, which may have complex effects on the dynamics and evolution of its declining populations.     

Clonal Plasticity in Response to Reciprocal Patchiness of Light and Nutrients in the Stoloniferous Herb Glechoma longituba L.

Interconnected ramets of clonal plants can functionally specialize in the uptake of resources from aboveground and/or underground sources. Ramet pairs of the clonal stoloniferous herb Glechoma Iongltuba L. were grown In spatially heterogeneous environments with complementary availability of light and nutrients. Plasticity with respect to root-shoot ratio, fitness-related traits （biomass, number of ramets and dry weight per ramet）, morphological traits （lamina area, root length） were experimentally examined. The aim was to understand the adaptation of G. Iongltuba to an environment with reciprocal patchiness of light and soil nutrients by plasticity In Its root-shoot ratio and clonal morphology. The results showed that the performance of ramets growing In patches with high light Intensity and low soil nutrients into the adjacent opposite patches was Increased in terms of fitness-related traits. However, the performance of those from patches with low light Intensity and high soil nutrients into the adjacent opposite patches was not changed. The root-shoot ratio and clonal morphology were plastic. Morphological traits such as lamina area and root length were altered In a way that enhanced the capture of light resources and soil nutrients. Apparent reciprocal resource transport between the ramets In an environment of reciprocal patchiness of resources can enhance the growth of ramets with complementary resource deficiencies.     

Genetic variation and clonal diversity of the endangered aquatic fern Ceratopteris pteridoides as revealed by AFLP analysis

Ceratopteris pteridoides (Hook.) Hieron. is an endangered aquatic homosporous fern in China. Genetic diversity and structure of eight populations collected from the mid-lower reaches of Yangtze River were investigated using amplified fragment length polymorphisms (AFLPs). A low level of gene diversity was found at the population level (P_p = 17.4%, H_E = 0.039 and I = 0.063), which possibly resulted from its high degree of inbreeding, clonal growth and short life history of this species. C. pteridoides contained high clonal diversity (PD = 0.757, D = 0.992). High population differentiation was revealed by partitioning of genetic diversity (G_ST = 0.707), and the AMOVA analysis consistently showed that 72.3% of the total genetic diversity was attributable to among-population diversity. Based on the genetic information from UPGMA cluster and principal coordinate analysis, two management units have been identified, and translocation within each management unit is recommended.