云南南部不同种源地小桐子遗传多样性的ISSR 分析

应用ISSR 分子标记方法对采自云南的8 个居群的小桐子( Jatropha curcas) 共158 个个体进行遗传多样性分析。8 个ISSR 引物共扩增到了67 个位点, 其中61 个是多态性位点。分析结果表明: (1) 云南小桐子的遗传多样性水平很高。在物种水平上, 平均每个位点的多态位点百分率PPB = 91.04% , 有效等位基因数N_e = 1.5244, Nei′s 基因多样性指数H_e= 0.3070, Shannon 多样性信息指数H_o = 0.4618; 在居群水平上, PPB = 55.04%, N_e = 1.3826, H_e = 0.2171, Shannon 多样性信息指数H_o = 0.3178。(2) 居群间的遗传分化低于居群内的遗传分化。基于Nei''s 遗传多样性分析得出的居群间遗传多样性分化系数G_st = 0.2944。AMOVA分析显示: 云南小桐子的遗传变异主要存在于居群内, 占总变异的63.50%, 居群间的遗传变异占36.50%。(3) 居群间的地理距离及遗传一致度并不存在相关性。鉴于以上指标, 我们推测云南小桐子可能来自不同的地区。     

准噶尔无叶豆片断化居群的遗传变异及克隆多样性

准噶尔无叶豆(Eremosparton songoricum)是豆科无叶豆属小半灌木, 既能开花结实进行有性繁殖, 又可以靠根茎进行无性克隆繁殖, 为国家三级保护植物, 在中国仅片断化分布于新疆古尔班通古特沙漠局部区域。本文采用ISSR分子标记对采自古尔班通古特沙漠腹地及边缘的7个准噶尔无叶豆自然居群共148个个体进行了遗传变异和克隆多样性分析。8个引物共扩增出84个位点, 其中77个为多态性位点, 物种水平上的多态位点百分比PPB为91.67％, Nei's基因多样性指数I为0.3192, Shannon信息指数H为0.3540; 居群水平上的多态位点百分比PPB为58.45％, Nei's基因多样性指数I为0.2248, Shannon信息指数H为0.3270。居群间的遗传分化系数G_ST为0.2978。AMOVA分析表明, 有31.88%的遗传变异存在于居群间, 表明居群间存在显著的遗传分化。克隆多样性分析表明, 居群水平上, 居群G的Simpson多样性指数和均匀度指数最高, 分别为0.9400和0.9885; 居群E最低, 分别为0.8457和0.9021。物种水平上, Simpson多样性指数为0.9858, 均匀度指数为0.9673。本研究结果表明, 和其他荒漠植物相比, 准噶尔无叶豆表现出较高的遗传变异水平和克隆多样性, 这主要与该物种兼性生殖的繁育方式及多克隆起源有关; 而居群间产生了显著的遗传分化则主要由于人为干扰引起的生境片断化和居群减小而导致的基因交流障碍所致。遗传变异水平和遗传结构的研究将为分析准噶尔无叶豆致濒原因及进化潜力提供重要资料, 对该物种保护具有指导意义。     

内蒙古地区刺叶柄棘豆(Oxytropis aciphylla Ledeb.)种群遗传多样性分析

用ISSR分子标记对内蒙古地区刺叶柄棘豆(Oxytorpis aciphylla Ledeb.) 5个地理种群进行了种群遗传多样性分析。结果表明：刺叶柄棘豆种群具有较高的遗传多样性,11个ISSR引物扩增出215条带,总的多态位点百分率为98.14%,Shannon多样性指数I=0.2108,Nei基因多样性指数 H=0.341 6,种内总基因多样性(H_t) 为0.2108,种群内基因多样性(H_s)为0.160 4, 大部分遗传变异(76.11%)的遗传变异存在于种群内, 23.89%的遗传变异存在于种群间。遗传分化系数(Gst)为0.238 9,基因流(Nm)为1.592 9。5个居群间已有遗传分化趋势,遗传漂变不会引起遗传分化。UPGMA遗传距离聚类结果表明, 5个地理种群中,植被类型为荒漠草原的4个种群之间遗传距离较近,与1个荒漠种群距离较远。     

鄱阳湖具刚毛荸荠居群遗传多样性和克隆结构的初步研究

采用ISSR标记对鄱阳湖的2个具刚毛荸荠(Heleocharis valleculosa f.setosa)居群共120个个体的遗传多样性和克隆结构进行了研究.5条ISSR引物共检测到85个位点,其中49个为多态位点,占57.65%.具刚毛荸荠具有较高的遗传多样性(在物种水平上,Nei's基因多样性指数H=0.1545,Shannon信息指数I=0.2400),两居群间遗传分化很小.具刚毛荸荠的克隆多样性很高(D=0.9975),两居群不具有共同的基因型.空间自相关分析表明,具刚毛荸荠居群内遗传变异为随机分布格局.     

武陵山区蛇足石杉遗传多样性的AFLP分析

采用AFLP分子标记对武陵山区蛇足石杉(Huperzia serrata)4个居群进行遗传多样性的研究,结果表明:(1)7对引物组合共扩增出条带615条,其中549条为多态性条带;在物种水平上,多态性条带百分率PPB=89.27%,有效等位基因数Ne=1.257,Nei’s基因多样度指数H=0.178,Shannon多样性信息指数Isp=0.298;在居群水平上,PPB=71.42%,Ne=1.235,H=0.154,Shannon多样性信息指数Ipop=0.251;遗传多样性在居群间有明显的差别,其中坪坝营(PBY)居群最高(PPB=81.95%),而铁峰山(TFS)居群最低(PPB=64.55%)。(2)居群间的遗传分化较低,基于Nei’s基因多样性分析结果显示,居群间遗传分化系数GST=0.159;Shannon’s居群分化系数[(Isp-Ipop)/Isp]为0.16;WINAMOVA分析显示,武陵山区蛇足石杉的遗传变异主要存在于居群内,居群内的遗传变异分量为65.057,占总变异的75.77%,而居群间的遗传变异分量为20.804,占总变异的24.23%;居群内存在极显著的遗传分化(ΦST=0.242,P0.001)。(3)由遗传分化系数(GST)估计,武陵山区蛇足石杉居群间的基因流Nm=2.647,表明蛇足石杉属于异交种。(4)两两居群间的Nei’s遗传一致度(IN)范围为0.031 0~0.969 4;Mantel检测结果显示,居群间的遗传距离与地理距离之间不存在显著的正相关关系(r=0.269,P=0.887)。研究认为,遗传多样性与遗传结构主要决定于居群历史,较少干扰而稳定的居群偏向克隆生殖,遗传多样性较低,而新建居群的遗传多样性则较高;克隆生长、生态位选择、异交,以及有效的孢子风媒传播等可能是其维持较高遗传多样性水平的因素,而过度采挖等人类活动和生境片断化是导致蛇足石杉濒危的主要因素。     

长竹蛏不同地理居群的遗传多样性

研究以大连、烟台、莱州、青岛和赣榆近海5个不同地理居群的长竹蛏(Solen strictus Gould)为实验材料,利用ISSR分子标记进行了遗传多样性的研究。结果表明,13个ISSR引物在5个居群中共扩增出200个位点,平均每个引物记录15.4个位点,5个居群的多态位点比例为43.56%—60.43%。长竹蛏在物种水平上的Nei’s基因多样性指数和Shannon’s信息指数分别为0.2854和0.4390,在居群水平上分别为0.1674和0.2530。NJ聚类分析显示,青岛居群与赣榆居群的亲缘关系最近,而烟台居群与其他4个居群的亲缘关系较远。经Mantel检测,长竹蛏5个居群间的遗传距离与地理距离并无相关性(r=-0.0834,P>0.1)。AMOVA分子变异分析表明,长竹蛏的遗传变异有47.71%发生在居群间,52.29%发生在居群内,居群内的遗传变异大于居群间的遗传变异。长竹蛏5个居群间的遗传分化系数(Gst)为0.2889,基因流(Nm)为1.3194。结果表明,长竹蛏具有较高的遗传多样性,但居群间已发生了一定程度的遗传分化。       

濒危植物三棱栎遗传多样性的RAPD分析

用随机扩增多态DNA (RAPD)标记对 5个三棱栎 (Trigonobalanusdoichangensis)居群共 99个个体进行遗传多样性和居群遗传结构分析。 16个引物共检测到 15 7个位点 ,其中多态位点 83个 ,占 5 2 87%。物种水平Shannon多样性指数I =0 2 4 31,Nei基因多样度h =0 15 95 ,种内总遗传变异量Ht=0 16 0 0 ,居群内遗传变异量Hs =0 0 74 9,居群间变异量大于居群内变异量 ,表明三棱栎的遗传变异主要存在于居群之间。与同科植物相比 ,三棱栎遗传多样性较低 ,遗传分化系数Gst =0 5 32 0 ,说明居群间的遗传变异占 5 3 2 0 % ,居群间已出现强烈的遗传分化。当地人的强烈活动造成的生境破碎化和居群隔离 ,以及三棱栎演化过程中的地史变化对其种群发展的影响等 ,可能是造成其居群间强烈的遗传分化和较低遗传多样性的原因。基于本研究结果 ,提出了三棱栎遗传多样性的保护策略。     

准噶尔无叶豆5个自然居群ISSR遗传变异的空间自相关分析

采用空间自相关分析方法对准噶尔无叶豆(Eremosparton songoricum)5个居群遗传变异的空间结构进行了研究。根据8对ISSR引物扩增的多态性位点,选择了基因频率在30–70%的ISSR位点,运用GenAlEx6和SAAP4.3软件以及地理距离间隔方法分别计算了5个居群的空间自相关系数。结果表明:准噶尔无叶豆居群具有明显的空间遗传结构,绝大多数ISSR位点变异呈非随机分布。位于沙漠腹地的B、D居群和位于沙漠东缘的F居群的遗传变异呈现渐变模式,分别在7m,7m及9m范围内个体呈现显著正相关,推测与克隆繁殖占绝对优势、有性更新罕见发生有关,而克隆大小的差别则主要由微生境差异所引起。位于沙漠北缘的G居群的遗传变异呈现双向渐变模式,在3m内个体呈现显著正相关,这与该居群实生幼苗增补密切相关,但花粉和种子的有限散布所导致的距离隔离对该居群空间遗传结构产生了重要影响。而沙漠腹地的A居群呈现衰退模式,是因为小居群增加了近交的几率,并引起了遗传漂变。     

云南泸定百合遗传多样性的表型与ISSR分析

用表型变异分析并结合ISSR分子标记对云南境内10个泸定百合(Lilium sargenttiae)居群进行遗传多样性分析。结果显示:(1)云南10个泸定百合居群的7个表型性状的居群间F值在3.26～19.1之间,表型的居群间差异均达到显著或极显著水平;平均表型分化系数为71.22%,居群间变异(59.92%)大于居群内变异(23.42%),说明居群间表型变异是泸定百合居群变异的主要来源。(2)13个ISSR引物共检测到248个多态位点,物种水平上多态位点率98.80%,Nei’s多样性指数和Shannon多样性指数分别为0.265 5和0.413 1;居群内基因多样度(Hs)为0.175 7,居群间基因分化系数(Gst)0.336 7,Mantel检验显示泸定百合居群在地理距离和遗传距离间具有显著相关性(r=0.804 4,P=0.009 9)。研究表明,云南泸定百合的居群间表型和分子水平均具有较高的遗传多样性,居群间的遗传分化较大,并且分化趋势具有明显的地域性。因此,可选择迁地种植对泸定百合进行有效保护。     

湖北野生天麻的遗传分化及栽培天麻种质评价

采用7条ISSR引物对天麻(Gastrodiaelata)8个自然居群和6个人工栽培居群共483个样本的居群遗传多样性进行了初步检测,共检测出清晰、重复性好的DNA带77条,其中64条为多态性带,总多态位点百分比PPB=83.12%。遗传多样性分析结果表明:天麻自然居群的遗传多样性参数分别为:多态位点百分比PPB=59.09%,有效等位基因数Ae=1.29,Nei’s遗传多样度H=0.176,Shannon’s多态信息指数I=0.270,明显高于人工栽培居群(PPB=35.71%,Ae=1.16,H=0.100,I=0.155),揭示出栽培居群存在明显的遗传基础狭窄和遗传均质性问题。UPGMA聚类分析表明,自然居群与栽培居群存在明显的分化而分别聚为两大类群。自然居群间基因分化系数GST=0.2558,与AMOVA分析所揭示的居群间遗传变异量占总变异的27.25%的结果相近,说明天麻自然居群间亦存在一定程度的遗传分化;居群间基因流(Nm)为1.4547,相对较弱,可能对自然居群的遗传分化有一定影响。自然居群聚类结果显示出一定程度的地理区域聚类趋势,但Mantel检验表明自然居群间遗传距离与地理距离并不存在显著相关(r=0.1669,P=0.2110),揭示出天麻自然居群的分化现状可能是其生活史特性、地理隔离与人为破坏综合作用的结果。栽培居群的遗传均质化趋势,揭示了引种驯化的瓶颈效应和长期无性繁育所导致的遗传多样性丧失,也反映出栽培天麻种质的遗传基础狭窄。而栽培居群与自然居群间存在着明显的遗传分化,反映天麻栽培居群与自然居群间可能存在基因流的阻断。     

Population genetic consequences of extreme variation in sexual and clonal reproduction in an aquatic plant

Most plants combine sexual reproduction with asexual clonal reproduction in varying degrees, yet the genetic consequences of reproductive variation remain poorly understood. The aquatic plant Butomus umbellatus exhibits striking reproductive variation related to ploidy. Diploids produce abundant viable seed whereas triploids are sexually sterile. Diploids also produce hundreds of tiny clonal bulbils, whereas triploids exhibit only limited clonal multiplication through rhizome fragmentation. We investigated whether this marked difference in reproductive strategy influences the diversity of genotypes within populations and their movement between populations by performing two large-scale population surveys (n = 58 populations) and assaying genotypic variation using random amplified polymorphic DNA (RAPDs). Contrary to expectations, sexually fertile populations did not exhibit higher genotypic diversity than sterile populations. For each cytotype, we detected one very common and widespread genotype. This would only occur with a very low probability (< 10-7) under regular sexual recombination. Compatibility analysis also indicated that the pattern of genotypic variation largely conformed to that expected with predominant clonal reproduction. The potential for recombination in diploids is not realized, possibly because seeds are outcompeted by bulbils for safe sites during establishment. We also failed to find evidence for more extensive movement of fertile than sterile genotypes. Aside from the few widespread genotypes, most were restricted to single populations. Genotypes in fertile populations were very strongly differentiated from those in sterile populations, suggesting that new triploids have not arisen during the colonization of North America. The colonization of North America involves two distinct forms of B. umbellatus that, despite striking reproductive differences, exhibit largely clonal population genetic structures.     

The importance of sexual and asexual reproduction in the recent evolution of Allium vineale

In the weedy plant species Allium vineale (wild garlic), individuals may simultaneously produce sexually and asexually derived offspring, by seed and bulbils, respectively. In this study, genetic and genotypic diversity was determined in samples from 14 European A. vineale populations using nuclear (RAPD) and cytoplasmic (PCR-RFLP of cpDNA) markers to investigate the importance of the different reproductive modes. In the whole sample, 77 nuclear multilocus genotypes and four chloroplast haplotypes (chlorotypes) were found. Populations exhibited a high degree of subdivision for nuclear and cytoplasmic markers as estimated from hierarchical F-statistics; at the same time, identical chlorotypes could be found in populations separated by large distances. Genotypic diversity was significantly lower than expected under free recombination in almost all populations, indicating that recruitment into populations is mostly by asexually produced offspring. Nevertheless, within each chlorotype, the distribution of markers from pairs of nuclear loci was incompatible with a purely clonal structure, suggesting that many multilocus genotypes have originated by sexual recombination rather than by mutation within asexual lineages. It is argued that the weedy habit of A. vineale is likely to have favored bulbil reproduction, whereas sexually generated genotypes may have facilitated local adaptation during the species' expansion across Europe.     

Asexual and sexual reproductive strategies in clonal plants

Most plants can reproduce both sexually and asexually (or vegetatively),and the balance between the two reproductive modes may vary widely between and within species.Extensive clonal growth may affect the evolution of life history traits in many ways.First,in some clonal species,sexual reproduction and sex ratio vary largely among populations.Variation in sexual reproduction may strongly affect plant's adaptation to local environments and the evolution of the geographic range.Second,clonal growth can increase floral display,and thus pollinator attraction,while it may impose serious constraints and evolutionary challenges on plants through geitonogamy that may strongly influence pollen dispersal.Geitonogamous pollination can bring a cost to plant fitness through both female and male functions.Some co-evolutionary interactions,therefore,may exist between the spatial structure and the mating behavior of clonal plants.Finally,a trade-off may exist between sexual reproduction and clonal growth.Resource allocation to the two reproductive modes may depend on environmental conditions,competitive dominance,life span,and genetic factors.If different reproductive modes represent adaptive strategies for plants in different environments,we expect that most of the resources should be allocated to sexual reproduction in habitats with fluctuating environmental conditions and strong competition,while clonal growth should be dominant in stable habitats.Yet we know little about the consequence of natural selection on the two reproductive modes and factors which control the balance of the two reproductive modes.Future studies should investigate the reproductive strategies of clonal plants simultaneously from both sexual and asexual perspectives.     

Causes and consequences of extreme variation in reproductive strategy and vegetative growth among invasive populations of a clonal aquatic plant, <Emphasis Type="Italic">Butomus umbellatus</Emphasis> L. (Butomaceae)

The mode of reproduction may influence the spread of invasive species by affecting evolutionary potential and dispersal ability. We sampled 51 introduced North American populations of the clonal aquatic plant Butomus umbellatus L. (flowering rush) and found extreme variation in sexual fertility caused by polyploidy. Populations consisted of diploids that produced thousands of viable seeds or of sexually sterile triploids. Although a trade-off between sexual and clonal reproduction predicts that the sexual sterility of triploids would be compensated for by greater clonal reproduction, a greenhouse experiment involving eight diploid and 10 triploid populations showed that diploid plants not only invest substantially in sexual structures but also make hundreds of tiny clonal bulbils on both rhizomes and inflorescences. In contrast, triploids do not make bulbils and have very limited scope for clonal multiplication and dispersal. Diploid populations were more frequent than triploid populations, especially in the Great Lakes region. This is probably because of the difference between cytotypes in clonal rather than sexual reproduction, as genetic analyses indicate a general lack of sexual recruitment in North America. Although triploids were less common, they have a wider geographical distribution. This could be due to a greater ecological tolerance resulting from polyploidy. However, genetic evidence suggests that triploids have become widespread via their use in and escape from horticulture. North America is being colonized by two distinct forms of B. umbellatus that differ strongly in reproductive strategy as well as the vectors and pathways of invasion.     

Genetic Diversity and Geographic Differentiation in the Threatened Species Dysosma pleiantha in China as Revealed by ISSR Analysis

Dysosma pleiantha, an important threatened medicinal plant species, is restricted in distribution to southeastern China. The species is capable of reproducing both sexually and asexually. In this study, inter-simple sequence repeat marker data were obtained and analyzed with respect to genetic variation and genetic structure. The extent of clonality, together with the clonal and sexual reproductive strategies, varied among sites, and the populations under harsh ecological conditions tended to have large clones with relatively low clonal diversity caused by vegetative reproduction. The ramets sharing the same genotype show a clumped distribution. Across all populations surveyed, average within-population diversity was remarkably low (e.g., 0.111 for Nei’s gene diversity), with populations from the nature reserves maintaining relatively high amounts of genetic diversity. Among all populations, high genetic differentiation (AMOVA: Φ_ST = 0.500; Nei’s genetic diversity: G _ST = 0.465, Bayesian analysis: Φ_B = 0.436) was detected, together with an isolation-by-distance pattern. Low seedling recruitment due to inbreeding, restricted gene flow, and genetic drift are proposed as determinant factors responsible for the low genetic diversity and high genetic differentiation observed.     

Reproductive strategy, clonal structure and genetic diversity in populations of the aquatic macrophyte Sparganium emersum in river systems

Many aquatic and riparian plant species are characterized by the ability to reproduce both sexually and asexually. Yet, little is known about how spatial variation in sexual and asexual reproduction affects the genotypic diversity within populations of aquatic and riparian plants. We used six polymorphic microsatellites to examine the genetic diversity within and differentiation among 17 populations (606 individuals) of Sparganium emersum, in two Dutch-German rivers. Our study revealed a striking difference between rivers in the mode of reproduction (sexual vs. asexual) within S. emersum populations. The mode of reproduction was strongly related to locally reigning hydrodynamic conditions. Sexually reproducing populations exhibited a greater number of multilocus genotypes compared to asexual populations. The regional population structure suggested higher levels of gene flow among sexually reproducing populations compared to clonal populations. Gene flow was mainly mediated via hydrochoric dispersal of generative propagules (seeds), impeding genetic differentiation among populations even over river distances up to 50 km. Although evidence for hydrochoric dispersal of vegetative propagules (clonal plant fragments) was found, this mechanism appeared to be relatively less important. Bayesian-based assignment procedures revealed a number of immigrants, originating from outside our study area, suggesting intercatchment plant dispersal, possibly the result of waterfowl-mediated seed dispersal. This study demonstrates how variation in local environmental conditions in river systems, resulting in shifting balances of sexual vs. asexual reproduction within populations, will affect the genotypic diversity within populations. This study furthermore cautions against generalizations about dispersal of riparian plant species in river systems.     

Sex after all: high levels of diversity detected in the arctic clonal plant Saxifraga cernua using RAPD markers

Arctic plants in general and arctic clonal plants in particular have often been assumed to contain low levels of genetic diversity. We used RAPDs (random amplified polymorphic DNAs) to investigate genetic diversity in the arctic-alpine Saxifraga cernua , which mainly reproduces clonally via bulbils, at three spatial scales in Svalbard: (i) 'macroscale', between two sites 11 km apart; (ii) 'mesoscale', along two crossing transects at each site; and (iii) 'microscale', within a 3 × 3 m square at each site. Thirteen putative clones (RAPD phenotypes) were distinguished among 93 ramets based on 38 RAPD markers. The genetic diversity ( D ; mean 0.52, range 0.10–0.81) and evenness ( E ; mean 0.42, range 0.00–0.82) were at the same level as in clonal plants in general. However, the diversity strongly depended on site and spatial scale. Several clones were highly divergent and clustered independently of site in UPGMA and PCO analyses. In an analysis of molecular variance ( AMOVA ), most of the variation (59%) was found within sites. Mantel tests revealed no correlation between spatial and genetic distance within sites. Our results suggest that occasional sexual reproduction as well as clonal migration via bulbil dispersal play a significant role in the treeless arctic environment, where S. cernua is widespread and locally very abundant. In contrast, Bauert et al. ( Molecular Ecology 7, 1519–1527) found no genetic variation within populations or regions of the Alps, where the species has highly isolated occurrences.     

Asexual and sexual reproductive strategies in clonal plants

Most plants can reproduce both sexually and asexually (or vegetatively), and the balance between the two reproductive modes may vary widely between and within species. Extensive clonal growth may affect the evolution of life history traits in many ways. First, in some clonal species, sexual reproduction and sex ratio vary largely among populations. Variation in sexual reproduction may strongly affect plant’s adaptation to local environments and the evolution of the geographic range. Second, clonal growth can increase floral display, and thus pollinator attraction, while it may impose serious constraints and evolutionary challenges on plants through geitonogamy that may strongly influence pollen dispersal. Geitonogamous pollination can bring a cost to plant fitness through both female and male functions. Some co-evolutionary interactions, therefore, may exist between the spatial structure and the mating behavior of clonal plants. Finally, a trade-off may exist between sexual reproduction and clonal growth. Resource allocation to the two reproductive modes may depend on environmental conditions, competitive dominance, life span, and genetic factors. If different reproductive modes represent adaptive strategies for plants in different environments, we expect that most of the resources should be allocated to sexual reproduction in habitats with fluctuating environmental conditions and strong competition, while clonal growth should be dominant in stable habitats. Yet we know little about the consequence of natural selection on the two reproductive modes and factors which control the balance of the two reproductive modes. Future studies should investigate the reproductive strategies of clonal plants simultaneously from both sexual and asexual perspectives. Translated from Acta Phytoecologica Sinica, 2006, 20(1): 174–183 [译自: 植物生态学报]     

CLONAL STRUCTURE,GENOTYPIC DIVERSITY,AND SEED PRODUCTION IN POPULATIONS OF FILIPENDULA RUBRA (ROSACEAE) FROM THE NORTHCENTRAL UNITED STATES

Queen of the prairie, Filipendula rubra (Rosaceae), is a clonal plant species inhabiting calcareous fens and wet meadows of the northcentral United States. F. rubra reproduces asexually by underground rhizomes and sexually by seed. While many studies have explored genotype diversity in clonal species with limited sexual reproduction, fewer have been conducted on clonal species with the potential for extensive sexual reproduction. We studied the relationship between the extent of sexual reproduction and genotype diversity. Although genotype diversity in F. rubra was double that reported by others for 27 nearly obligate clonal plant species, it was still quite low. For 25 populations studied, the mean number of genotypes was 5.5 (range = 1–15; SE = 0.964) and the average proportion of distinguishable genotypes was 0.38 (range = 0.03–1.00; SE = 0.07). The production of viable seed was quite variable among populations (mean proportion of viable seeds = 0.242; range = 0.002–0.565; SE = 0.04). Considering that some inflorescences can produce over 5,000 seeds, the potential for recruitment of sexually produced individuals is very large. No correlation was found between seed production and genotype diversity as was expected in a self-incompatible species in which one-third of the populations possessed a single genotype. It was hypothesized that the low genotype diversity found in numerous populations may be due to competition limiting recruitment of new seedlings.     

genotype and genodive: two programs for the analysis of genetic diversity of asexual organisms

Investigating diversity in asexual organisms using molecular markers involves the assignment of individuals to clonal lineages and the subsequent analysis of clonal diversity. Assignment is possible using a distance matrix in combination with a user‐specified threshold, defined as the maximum distance between two individuals that are considered to belong to the same clonal lineage. Analysis of clonal diversity requires tests for differences in diversity and clonal composition between populations. We developed two programs, genotype and genodive for such analyses of clonal diversity in asexually reproducing organisms. Additionally, genotype can be used for detecting genotyping errors in studies of sexual organisms.