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。     

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.     

黄花杓兰云南中甸居群遗传结构及克隆多样性的分析

采用AFLP分子标记方法对云南中甸的6个黄花杓兰( Cypripedium flavum )居群进行了遗传多样性水平、遗传结构及克隆多样性研究,其中两个居群用样方取样法分析其克隆空间结构.POPGENE软件分析结果表明:两组引物共产生104个位点,其中86个为多态位点,多态位点百分率为82.69%.黄花杓兰具有丰富的遗传变异(物种水平上, He=0.2884, Ho=0.4312;居群水平上,P=64.59%, He=0.2449, Ho=0.3606),黄花杓兰居群的遗传分化不大( Gst=0.154),居群间基因交流较为频繁( Nm=2.7460).居群的克隆多样性水平高( D=0.9638-0.9960,G/N=0.83-0.96),同一克隆的分株相邻,克隆生长延伸范围狭窄.黄花杓兰居群之所以保持较高水平的遗传多样性,可能与其既能通过实生幼苗增加基因的杂合度,又能通过无性分株把杂合体固定下来有关.     

濒危物种胡杨和灰叶胡杨的克隆生长特征

研究不同生态环境条件下胡杨和灰叶胡杨横走侧根的空间分布及其形态特征、不定芽及克隆分株的数量格局特征及其与土壤水分的关系。研究结果表明:(1)16团3个生境中灰叶胡杨克隆分株所在横走侧根均分布在10—20cm的土层;阿瓦提混交林内灰叶胡杨和胡杨克隆分株所在横走侧根分布在20—40cm的土层;轮台县河道边胡杨克隆分株所在横走侧根分布在10—20cm的土层,林内胡杨克隆分株所在横走侧根分布在20—40cm的土层。不定芽、克隆分株所在部位横走侧根最粗,向两端逐渐变细,且远端根始终比近端根要粗;(2)不定芽具有以前期克隆分株为中心向两端延伸发生分布的空间格局特征,横走侧根上不定芽数与出土克隆分株数呈极显著正相关,未出土克隆分株数与出土克隆分株数呈显著正相关,说明不定芽、未出土克隆分株的数量都直接影响出土克隆分株的数量。(3)不定芽、未出土克隆分株和出土克隆分株出现频率、空间分布范围在同一生境同一根段均表现为不定芽未出土克隆分株出土克隆分株,在不同研究区表现为16团(地下水位1.08m)轮台县(地下水位2.56m)阿瓦提县(地下水位3.34m);相关分析显示土壤水分含量与不定芽和出土克隆分株数量均呈极显著正相关。综合分析认为,地下水位和土壤含水量均对不定芽发生以及不定芽向克隆分株转化有显著的影响。     

竹叶眼子菜居群遗传多样性和克隆结构

采用ISSR技术对长江中游南岸豹澥湖和大冶湖不同生境中的竹叶眼子菜(Potamogeton malaianus)居群的遗传多样性及克隆结构进行了研究.结果表明,在两居群的106株个体中,利用6条ISSR引物共得到40条符合3/N标准并无连锁不平衡的清晰位点,竹叶眼子菜具有较高的遗传多样性,其多态位点百分率为75.0％,Shannon多样性指数为0.3736, 两居群的遗传分化很小.竹叶眼子菜的克隆多样性很高(D=0.9917),两居群间的克隆分化很大,不具有共有的基因型.竹叶眼子菜的基株分布为游击型构型,位于湖心的大冶居群克隆距离(3.0～31.5 m)明显地大于湖岸豹澥居群(2.4～6.7 m).     

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.     

模拟采食干扰下克隆整合对两种箭竹分株种群更新的影响

动物对植物的采食会刺激植物进行补偿性更新生长, 克隆整合效应能够通过分株之间的物质传输增强克隆植物的这种补偿生长。现今对克隆整合效应在箭竹(Fargesia)补偿更新中的作用仍未得到全面认识。2011年10月到2012年11月, 设立了糙花箭竹(Fargesia scabrida)和缺苞箭竹(F. denudata)各40个样方, 分别进行不剪除样方内分株和剪除样方内分株数量的25%、50%、75%四种模拟采食干扰处理, 并将样方四周的根状茎切断或保持连接。从2012年6月起观测并统计了箭竹分株种群的累积出笋率、总出笋率、补充率, 以及新生分株的株高、基径和单株生物量。结果表明: (1)在不剪除分株的样方, 切断根状茎连接显著增加了糙花箭竹的出笋率和补充率, 但降低了新生分株的株高和单株生物量, 也显著降低了缺苞箭竹的出笋率和补充率; (2)保持根状茎连接时, 25%的剪除强度仅仅降低了糙花箭竹新生分株的单株生物量; 同样在保持根状茎连接的条件下, 25%、50%的剪除强度使缺苞箭竹种群的补充率有所降低, 而切断根状茎后缺苞箭竹在25%的剪除强度下的分株补充率反而升高; (3) 75%的剪除强度并未影响两种箭竹新生分株数量更新, 但造成新生分株质量显著下降; 切断根状茎连接显著降低了糙花箭竹的新生分株的株高和基径, 对缺苞箭竹影响不显著。实验证明克隆整合影响了两种箭竹新生分株的萌发、存活和生长, 但不是两种箭竹进行补偿更新的主要机制, 仅在糙花箭竹分株种群受到重度采食干扰后的更新中才起到明显的促进作用; 两种箭竹均能在50%的剪除强度下通过补偿生长恢复种群的稳定, 75%的剪除强度则会造成箭竹新生分株质量的下降。     

贺兰山丁香自然居群克隆生长格局及遗传多样性的ISSR分析

运用ISSR分子标记技术,通过制定挖掘采样、"+"形采样及"垂直"采样3种采样方案,对贺兰山丁香(Syringa pinnatifolia var.alanshanica)不同居群的克隆多样性、克隆生长格局及其遗传多样性进行了分析.克隆多样性分析表明:挖掘采样方式采到的3个克隆系内,各自所包含的单株间具有完全相同的基因型;"垂直"采样及"+"形采样的7个居群、 239个样品表现出136个不同的基因型或克隆,显示贺兰山丁香具有较高的克隆多样性(D=0.994)及基因型分布均匀性(E=0.985).克隆生长空间格局分析表明,贺兰山丁香为密集型克隆植物.每个居群都由多克隆组成,克隆生长只发生在同一丛内,多数基株只含有1个分株,最多可达8个.物种水平上的平均克隆大小(N_C)和平均基因型比例(PD)分别为1.757和0.569.对贺兰山丁香遗传多样性分析的结果显示,在居群水平和物种水平上都保持着较高的遗传多样性,其遗传变异主要存在于居群内;但居群间分化程度较低(G_ST=0.320),表明自然居群间基因交流有限.     

青藏高原东缘过路黄在资源交互斑块性生境中的克隆内资源共享

在青藏高原和四川盆地过渡带,分别于618m和1800m两个海拔高度上研究匍匐茎克隆植物过路黄(Lysimachia christinae)在资源交互斑块性生境中的克隆内资源共享及其对生长的影响.结果显示, 在海拔1800m处,与资源的空间同质性处理(Ⅰ) 和(Ⅱ)相比, 资源的空间异质性处理(Ⅲ)和(Ⅳ)下过路黄整个克隆片段的生物量和分株数均获得显著增加;在海拔618m处,与资源的空间同质性处理(Ⅰ) 和(Ⅱ)相比,资源的空间异质性处理(Ⅲ)和(Ⅳ)下过路黄整个克隆片段生物量显著增加.在海拔618m和1800m处,生长在低光高养条件下的远端分株, 若与高光低养的近端分株相连, 相比连接到低光高养的近端分株, 它们分配更多的生物量到地下部分;在海拔1800m处,生长在高光低养条件下的远端分株, 若与低光高养的近端分株相连, 相比连接到高光低养的近端分株, 它们分配更多的生物量到地上部分.在海拔618m和1800m处,生长在高光低养条件下的近端分株, 若与低光高养的远端分株相连, 相比连接到高光低养的远端分株, 它们分配更多的生物量到地上部分.处于资源交互斑块性生境中的过路黄发生了克隆内分工,依靠相连分株间的功能分化, 克隆植物能有效的利用异质性分布的资源, 缓解资源交互斑块性分布对克隆植物生长的不利影响.通过间隔子(匍匐茎或根状茎),相连分株间能够相互传递和共享由不同分株获得的资源,这种资源共享能够提高克隆植物在异质性生境中的存活与生长.同时,方差分析显示环境异质性和海拔的交互作用显著影响克隆片段的生物量和分株数.相比于海拔618m,在海拔1800m处克隆内资源共享对克隆植物生长表现的影响更大.     

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。     

Floral distribution,clonal structure,and their effects on pollination success in a self-incompatible <Emphasis Type="Italic">Convallaria keiskei</Emphasis> population in northern Japan

In plant species, when clonal growth produces a patchy structure and flowering ramets are clustered, the amount of pollen contributing to reproductive success is often regulated by pollinator efficiency and geitonogamy. The spatial population structure may influence reproductive success. We examined the clonal structure, the spatial ramet distribution, and their combined effects on fruit set in a natural population of the insect-pollinated, self-incompatible clonal herb, Convallaria keiskei, in northern Japan. The number of shoots, flowers, and fruits in 1-m² quadrats were counted at every 5 m grid point in an established 100 × 90-m study plot. From all the quadrats where shoots existed, leaf samples were collected for allozyme analysis. Using the two spatial parameters of flowering ramet densities and genotypes, we then constructed individual-based fruit-set models. A total of 236 quadrats contained shoots, and 135 contained flowering ramets, which indicated expanded distribution of this plant throughout the study plot, while shoots, flowers and fruits all showed clustering distributions. Allozyme analysis of 282 samples revealed 94 multilocus genotypes. The largest clone extended to more than 40 m, whereas 56 genotypes were detected in only one sample. Several large clones and many small clones were distributed close to each other. Fine-scale spatial modelling revealed that the neighbouring flower numbers of different genotypes, compared with local genet or flower diversity, more influenced fruit set, in which the range of the neighbour was 14.5 m. These findings indicate that the compatible pollen dispersed by insect pollinators has a significant effect on sexual reproduction, in this C. keiskei population. Consequently, the spatial structure, which includes both genet distribution and clonal expansion by ramets, had a significant effect on pollination success.     

Clonal Diversity and Fine‐scale Genetic Structure in a High Andean Treeline Population

Clonal propagation becomes more abundant with increasing altitudes as environmental conditions worsen. To date, little attention has been paid to the way in which clonal propagation affects genetic diversity and the fine‐scale spatial genetic structure (FSGS) of clonal alpine trees. An AFLP study was undertaken to quantify the clonal and genetic diversity and FSGS of the vulnerable treeline species Polylepis reticulata in Ecuador. We successfully genotyped 32 and 75 ramets within 4 m × 100 m (coarse scale) and 4 m × 4 m (fine scale) transects of one population, respectively. Higher genotypic diversity was detected at the coarse scale than at the fine scale, while lower genetic diversity was detected for P. reticulata than other Polylepis spp. at both scales. Significantly stronger FSGS was detected at the ramet level than the genet level for P. reticulata within a spatial distance of 3 m. The studied P. reticulata population showed pronounced FSGS (Sp = 0.012 at the genet level, a statistic reflecting declining pairwise kinship with distance) revealed restricted gene dispersal, which implies restricted seed dispersal for this population, assuming pollen flow is as extensive as that described for other wind‐pollinated tree species. Our results revealed that clonal diversity is a function of both sample size and the spatial scale of the sampling area. The findings highlights that clonal propagation has affected FSGS within a spatial distance of 3 m for this species.     

EFFECTS OF FIRE ON CLONAL GROWTH AND DYNAMICS OF PITYOPSIS GRAMINIFOLIA (ASTERACEAE)

The rhizomatous perennial Pityopsis graminifolia was studied in a Florida sandhill community in an annually burned site, a periodically burned site, and a site that has been protected from fire since 1965. These different fire regimes significantly affected the demography and life histories of both plants and plant parts in this clonal species. Fires resulted in reductions in ramet biomass and height, and an increase in the (root + rhizome)/shoot biomass ratio. Burning also decreased the total number of flower heads and new rhizomes produced per ramet. However, the survivorship of initiated rhizomes was greater in burned sites and resulted in a larger number of established daughter ramets per clone. As a result, in burned sites there was a shift in clone structure toward larger numbers of smaller ramets, but there were no significant reductions in seed or rhizome production on a per genet basis. The results showed that the responses to fire in P. graminifolia are different when measured at the genet vs. ramet level and that the effects of fire on clones can be explained by demographic responses of plant parts. Population regeneration in the study sites was dependent on successful clonal ramet production because no seedling recruitment was observed. This suggests that disturbances other than fire are important for new genet recruitment in these clonal populations.     

Clonality strongly affects the spatial genetic structure of the nurse species Aechmea nudicaulis (L.) Griseb. (Bromeliaceae)

Aechmea nudicaulis is a clonal bromeliad common to the Brazilian Atlantic forest complex and is found abundantly in the sandy coastal plain vegetation (restinga) on the north coast of Rio de Janeiro state, Brazil. This restinga site is structured in vegetation islands, and the species plays a key role as a nurse plant, much favoured by its clonality. We studied the clonal structure and consequences of clonality on the population spatial genetic structure (SGS) of this species using six nuclear microsatellites. Spatial autocorrelation analysis was performed to study the effects of sexual and clonal reproduction on the dispersal of A. nudicaulis. Analyses were performed at the genet (i.e. excluding clonal repeats) and ramet levels. Genotypic richness was moderate (R = 0.32), mostly as a result of the dominance of a few clones. The spatial distribution of genets was moderately intermingled, the mean clone size was 4.9 clonal fragments per genet and the maximum clonal spread was 25 m. Expected heterozygosities were high and comparable with those found in other clonal plants. SGS analyses at the genet level revealed significantly restricted gene dispersal (Sp = 0.074), a strong SGS compared with other herbaceous species. The clonal subrange extended across 23 m where clonality had a significant effect on SGS. The restricted dispersal and SGS pattern in A. nudicaulis, coupled with high levels of genetic diversity, indicated a recruitment at windows of opportunity (RWO) strategy. Moreover, the spatial distribution of genetic variation and the habitat occupation pattern in A. nudicaulis were dependent not only on the intrinsic biological traits of the species (such as spacer size and mating system), but also on biotic interactions with neighbouring species that determined suitable habitats for germination and the establishment of new genets. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 178 , 329–342.     

Clonality in the Endangered <Emphasis Type="Italic">Ambrosia pumila</Emphasis> (Asteraceae) Inferred from RAPD Markers; Implications for Conservation and Management

Clonal plants have the ability to spread and survive over long periods of time by vegetative growth. For endangered species, the occurrence of clonality can have significant impacts on levels of genetic diversity, population structure, recruitment, and the implementation of appropriate conservation strategies. Here we␣examine clone structure in three populations of Ambrosia pumila (Nutt.) Gray (Asteraceae), a federally endangered clonal species from southern California. Ambrosia pumila is a perennial herbaceous species spreading from a rhizome, and is frequently found in dense patches of several hundred stems in a few square meters. The primary habitat for this species is upper terraces of rivers and drainages in areas that have been heavily impacted by anthropogenic disturbances and changing flood regimes. RAPD markers were employed to document the number and distribution of clones within multiple 0.25 m² plots from each of three populations. Thirty-one multi-locus genotypes were identified from the 201 stems sampled. The spatial distribution of clones was limited with no genotypes shared between plots or populations. Mean clone size was estimated at 9.10 ramets per genet. Genets in most plots were intermingled, conforming to a guerrilla growth form. The maximum genet spread was 0.59 m suggesting that genets can be larger than the sampled 0.25 m² plots. Spatial autocorrelation analysis found a lack of spatial genetic structure at short distances and significant structure at large distances within populations. Due to the occurrence of multiple genets within each population, the limited spread of genets, and a localized genetic structure, conservation activities should focus on the maintenance of multiple populations throughout the species range.     

Simulations of clonal species genotypic diversity – trembling aspen (Populus tremuloïdes) as a case study

We built two models to follow clonal species genotypic diversity (G/N) over long periods of time at the stand and landscape levels. The models were then validated with empirical data from trembling aspen (Populus tremuloides) populations in Quebec’s boreal forest. Data was collected using a chronosequence approach in seven sites that burned in 1717, 1760, 1797, 1823, 1847, 1944, and 1916. Genetic identification was done by using four microsatellite loci. At the stand scale, simulations were repeated for a genet size of 5, 25, 50 and 100 ramets each. At the landscape level, we simulated the cumulative genet survival rate under different fire cycles (5–500 years) for 500 years after fire. Stand simulations indicated that ramet mortality within genets rather than genet mortality accounts for the increase in G/N with time since fire. Both the initial genet size and the recurrent suckering of some genets (or ramet recruitment) play an important role in maintaining high G/N levels for long periods of time. In general, the larger the number of ramets per genet, the longer the genet survives under a gap disturbance regime and a minimum of 100 ramets per genet is required to maintain aspen genet survival for 500 years. At the landscape level, genet loss increases as the fire cycle gets longer. In Quebec’s boreal forest, short rotation even-aged management practices seem to maintain a genet survival rate similar to that produced by the natural succession regime.     

Dynamics of distribution and performance of ramets constructing genets: a demographic�Cgenetic study in a clonal plant, Convallaria keiskei

Background and Aims

In clonal plants producing vegetative offspring, performance at the genet level as well as at the ramet level should be investigated in order to understand the entire picture of the population dynamics and the life history characteristics. In this study, demography, including reproduction and survival, the growth patterns and the spatial distributions of ramets within genets of the clonal herb Convallaria keiskei were explored.

Methods

Vegetative growth, flowering and survival of shoots whose genets were identified using microsatellite markers were monitored in four study plots for 3 years (2003–2005). The size structures of ramets in genets and their temporal shifts were then analysed. Their spatial distributions were also examined.

Key Results

During the census, 274 and 149 ramets were mapped in two 1 × 2 m plots, and 83 and 94 ramets in two 2 × 2 m quadrats. Thirty-eight genotypes were identified from 580 samples. Each plot included 5–18 genets, and most ramets belonged to the predominant genet(s) in each plot. Shoots foliated yearly for several years, but flowering ramets did not have an inflorescence the next year. A considerable number of new clonal offspring persistently appeared, forming a bell-shaped curve of the size structure of ramets in each genet. Comparing the structures modelled by the normal distributions suggested variation among ramets belonging to a single genet and variation among genets. Furthermore, spatial analyses revealed clumped and distant distributions of ramet pairs in a genet, in which the distant patterns corresponded to the linearly elongating clonal growth pattern of this species.

Conclusion

Characteristics of ramet performances such as flowering and recruitment of clonal offspring, in addition to growth, played a large part in the regulation of genet dynamics and distribution, which were different among the studied genets. These might be characteristics particularly relevant to clonal life histories.Key words: Clonal plant, Convallaria keiskei, demography, genet, genetic identification, growth pattern, life history, ramet, spatial distribution     

Clonal and spatial genetic structure within populations of a coastal plant, Carex kobomugi (Cyperaceae)

Clarification of clonal growth pattern is critical for understanding the population dynamics and reproductive system evolution of clonal plant species. The contribution of clonality to the spatial genetic structure (SGS) within populations is also an important issue. I examined the spatial distribution of genetic variability within two populations of the coastal plant Carex kobomugi using seven microsatellite loci. Genotyping of 226 and 140 ramets within 14 × 40 m and 14 × 34 m plots on two populations revealed 36 and 33 multilocus genotypes, respectively. To quantify the extent of intermingling among clones, for each genet, I calculated the dominance of ramets belonging to a particular genet within a spatial range of the genet. Furthermore, I analyzed spatial distribution of genotypes within 2 × 2 m and 1 × 2 m quadrats using second-order spatial statistics. These analyses indicated that clones are highly intermingled, suggesting a low level of spatial interaction among clones. Spatial autocorrelation analysis of kinship coefficient including all pairs of ramets showed significantly stronger SGS than analysis considering only pairs between different genets. I conclude that clonal propagation largely contributes to SGS at a fine scale.     

Influences of the genetic neighborhood on ramet reproductive success in a clonal desert cactus

Clonal structure in clonal plants can affect sexual reproduction. Individual ramets can decrease reproduction if their neighbors are ramets of the same genet due to inbreeding depression or self-incompatibility. We assessed ramet reproductive success in the partial self-incompatible Ferocactus robustus (Cactaceae) as a function of floral display size in focal ramets and floral display size and clonal structure of their reproductive neighborhoods. Ramets were labeled, sized in number of stems, mapped and genetically identified through RAPD markers in one population. A pollen dispersal area of 15-m radius was established for each ramet to determine the clonal diversity in the neighborhoods. Flower production and fruit set were counted on a monthly basis during one reproductive season as a surrogate of ramet fitness. We expected a decrease in individual ramet reproductive success as a function of the number of reproductive ramets of the same genet in the neighborhood. A total of 272 sampled ramets revealed 116 multilocus genotypes, showing high clonal diversity in the population (G/N = 0.43, D = 0.98). Clonal diversity of neighborhoods ranged from 0.06 to 1 and fruit set varied from 0 to 76.9%. Individual ramet reproductive success was influenced by (1) mate availability, (2) floral display size of a genet within the reproductive neighborhood, and (3) the proportion of distinguishable genotypes. Floral display size of genets and ramets coupled with the genetic diversity within the reproductive neighborhood determines the low sexual reproduction in F. robustus.