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1.
近缘物种的遗传多样性及其亲缘关系的取样策略研究   总被引:3,自引:2,他引:1  
取样策略的问题目前大多停留于对单一物种的种质资源研究.然而,对野生近缘植物取样策略的研究,不仅有利于准确快捷地阐明物种间的系统发育关系,而且对于了解遗传多样性分布状况,制定野外考察、材料收集取样及保护策略均有重要的理论指导意义.以巴山松及其近缘种为例,利用cpSSR(叶绿体微卫星)和AFLP2种分子标记对其取样策略和统计方法进行分析,揭示居群取样个体数和基因位点数与遗传多样性的关系以及基因(引物)和系统树构建方法对亲缘关系确定的影响.研究表明:(1)居群取样个体数和基因位点数差异对遗传多样性影响并不显著,但当居群取样个体数为30个左右,单引物基因位点数为60个以上,总位点数为480个以上时,所得遗传多样性及亲缘关系较为准确可靠.(2)较多数目的基因(引物)对于得到较为准确可靠的亲缘关系分析是十分必要的.(3)系统树构建方法对近缘种亲缘关系的确定有一定的影响.  相似文献   

2.
为了有效地保护野大豆(Glycine soja Sieb.et Zucc.)并制定合理的居群取样策略,对上海江湾机场的一个人然野大豆居群进行了 100个单株(个体)的随机取样,并用ISSR分子标记对其进行了遗传多样性分析.利用筛选出的15条ISSR引物在这个居群中检测到较高的遗传变异,样本内个体间的相似系数变化在0.17~0.89之间.居群内平均每个位点的平均预期杂合度(He)为0.171 4,香农指数(I)为0.271 4.PCA分析显示,江湾野大豆居群内的遗传变异不是呈均匀分布,而是呈从状分布.该野大豆居群遗传多样性和样本内个体数量间的相关性分析显示:在个体数少于40的情况下,遗传多样性随个体数的增加而迅速增加;当样本中的个体数大于40时,遗传多样性的增加减慢并很快趋于饱和.研究表明:对野大豆居群进行异地保护时,对各居群的采样植株数不应当低于35~45;在居群内采样时,所采集的个体之间最好相隔一定的空间距离.  相似文献   

3.
利用ISSR标记研究野大豆居群内遗传变异及其取样策略   总被引:20,自引:0,他引:20  
为了有效地保护野大豆(Glycine soja Sieb.et Zucc.)并制定合理的居群取样策略,对上海江湾机场的一个天然野大豆居群进行了100个单株(个体)的随机取样,并用ISSR分子标记对其进行了遗传多样性分析。利用筛选出的15条ISSR引物在这个居群中检测到较高的遗传变异,样本内个体间的相似系数变化在0.17~0.89之间。居群内平均每个位点的平均预期杂合度(He)为0.1714,香农指数(I)为0.2714。PCA分析显示,江湾野大豆居群内的遗传变异不是呈均匀分布,而是呈丛状分布。该野大豆居群遗传多样性和样本内个体数量间的相关性分析显示:在个体数少于40的情况下,遗传多样性随个体数的增加而迅速增加:当样本中的个体数大于40时,遗传多样性的增加减慢并很快趋于饱和。研究表明:对野大豆居群进行异地保护时,对各居群的采样植株数不应当低于35~45;在居群内采样时,所采集的个体之间最好相隔一定的空间距离。  相似文献   

4.
高洁  李巧明 《生物多样性》2008,16(3):271-278
羽叶金合欢(Acacia pennata)是一种重要的经济植物。本研究使用微卫星(SSR)分子标记技术对分布于云南西双版纳地区的7个羽叶金合欢自然居群进行了遗传多样性和居群遗传结构的研究,旨在从分子水平探讨其自然居群的遗传多样性,制定科学的保护策略,为今后的持续利用提供科学依据。我们用筛选出的6对SSR引物对采自7个自然居群的124个个体进行了扩增,共检测到23个等位基因。平均观察等位基因数(Na)为3.381,有效等位基因数(Ne)为2.460,平均期望杂合度(He)为0.573,Nei’s多样性指数(h)为0.567。其中景洪居群具有较高的遗传多样性,曼腊居群遗传多样性相对较低。遗传分化系数FST仅为0.113。结果表明羽叶金合欢的自然居群具有较高的遗传多样性水平,居群间分化较小,遗传变异主要来源于居群内。羽叶金合欢为多年生植物,分布范围广泛,这可能是其具有较高水平遗传多样性的原因;同时其繁育系统可能为异交,种子可远距离传播,这些特性也可能导致其较高的遗传多样性水平和较低的居群遗传分化。我们建议在对羽叶金合欢进行迁地保护时,要在遗传多样性较高的居群内进行大量取样,同时也要对不同居群进行取样。  相似文献   

5.
濒危植物鹅掌楸(Liriodendron chinense)目前仅零散分布于我国亚热带及越南北部地区,残存居群生境片断化较为严重。研究濒危植物片断化居群的遗传多样性及小尺度空间遗传结构(spatial genetic structure)有助于了解物种的生态进化过程以及制定相关的保育策略。本研究采用13对微卫星引物,对鹅掌楸的1个片断化居群进行了遗传多样性及空间遗传结构的研究,旨在揭示生境片断化条件下鹅掌楸的遗传多样性及基因流状况。研究结果表明:鹅掌楸烂木山居群内不同生境斑块及不同年龄阶段植株的遗传多样性水平差异不显著(P0.05),居群内存在寨内和山林2个遗传分化明显的亚居群。烂木山居群个体在200 m以内呈现显著的空间遗传结构,而2个亚居群内的个体仅在20 m的距离范围内存在微弱或不显著的空间遗传结构。鹅掌楸的空间遗传结构强度较低(Sp=0.0090),且寨内亚居群的空间遗传结构强度(Sp=0.0067)要高于山林亚居群(Sp=0.0053)。鹅掌楸以异交为主,种子较轻且具翅,借助风力传播,在一定程度上降低了空间遗传结构的强度。此外,居群内个体密度及生境特征也对鹅掌楸的空间遗传结构产生了一定影响。该居群出现显著的杂合子缺失,近交系数(FIS)为0.099(P0.01),表明生境片断化的遗传效应正逐渐显现。因此,对鹅掌楸的就地保护应注意维护与强化生境的连续性,促进基因交流。迁地保护时,取样距离应不小于20 m,以涵盖足够多的遗传变异。  相似文献   

6.
小麦族中间鹅观草不同居群的形态多样性分析   总被引:2,自引:0,他引:2  
小麦族(Triticeae)植物的野外调查、收集通常是以形态学为依据的。为了探讨小麦族植物在野外调查、收集的科学取样策略,本项研究以小麦族具有自花授粉习性的3个中间鹅观草(Roegneria sinica.vat.media Keng)居群、每个居群30个单株为材料,对11个形态学性状的多样性进行了分析。结果表明,3个居群的总遗传多样性指数为1.991,遗传多样性主要集中于居群内(91.76%),而居群间的遗传变异(8.24%)相对较小;不同取样梯度下的遗传多样性指数随单株取样数目的增加呈现增大趋势,但当取样数目达到18株时,遗传多样性指数达到最高值。上述结果说明,对于小麦族自花授粉植物野外调查、收集时,应以居群为单位,而且每一居群至少应调查、收集18个单株,才能代表居群的遗传多样性。以形态学为依据的取样策略的建立,对于指导野外调查、收集具有现实意义。  相似文献   

7.
小麦族(Triticeae)植物的野外调查、收集通常是以形态学为依据的。为了探讨小麦族植物在野外调查、收集的科学取样策略,本项研究以小麦族具有自花授粉习性的3个中间鹅观草(Roegneria sinica. var. media Keng)居群、每个居群30个单株为材料,对11个形态学性状的多样性进行了分析。结果表明,3个居群的总遗传多样性指数为1.991,遗传多样性主要集中于居群内(91.76%),而居群间的遗传变异(8.24%)相对较小;不同取样梯度下的遗传多样性指数随单株取样数目的增加呈现增大趋势,但当取样数目达到18株时,遗传多样性指数达到最高值。上述结果说明,对于小麦族自花授粉植物野外调查、收集时,应以居群为单位,而且每一居群至少应调查、收集18个单株,才能代表居群的遗传多样性。以形态学为依据的取样策略的建立,对于指导野外调查、收集具有现实意义。  相似文献   

8.
采用ISSR分子标记技术研究了干热河谷地区(云南的元江、元谋、巧家、保山4个居群)、干热地区(广西、海南2个居群)和湿热地区(西双版纳1个居群)木棉(Bombax malabaricum)居群的遗传多样性。用筛选出的10条引物,对110个个体进行了扩增,共检测到142个位点,多态位点百分率PPB=90.14%,Nei′s基因多样性指数H=0.2530,Shannon′s信息指数I为0.3864;居群间的遗传分化系数GST=0.1870,用AMOVA分析得出的Фst=0.177;研究结果表明木棉具有较高水平的遗传多样性,而居群间的遗传分化较低。我们推断木棉丰富的遗传多样性和有效的基因流是其较好适应性的重要因素。此外,我们建议在干热河谷地区对木棉进行引种时,要在居群内大量取样,并尽可能对不同居群进行取样。  相似文献   

9.
红花玉兰种质资源遗传多样性初探   总被引:3,自引:0,他引:3  
采用AFLP分子标记对目前仅发现在湖北五峰狭域分布的红花玉兰种质资源的遗传多样性进行了研究.用10对引物对6个居群的43个个体进行了选择性扩增,共检测到623个有效位点,其中多态位点595个.结果表明:在物种水平上,红花玉兰的遗传多样性水平很高,多态位点百分率达95.51%,Nei s基因多样度(HT)为0.211 0±0.028 6;红花玉兰的遗传变异主要存在于居群内,居群间的遗传分化较小.AMOVA分析表明总变异的93.37%存在于居群内,居群间的变异只占总变异的6.63%.Nei s遗传分化系数(GST)为0.191 9,居群间基因流(Nm)2.105 5.鉴于红花玉兰总体遗传多样性水平很高,而居群数目及居群内个体数量均很少,应该对红花玉兰各居群的所有个体实施及时的就地保护,并对其生境进行保护;并在原产地营建基因保存林,营建时应加大各居群内的取样数量,使得红花玉兰较高的遗传多样性得到保存;同时积极开展异地引种栽培,使红花玉兰在观赏应用中得到切实的保护.  相似文献   

10.
濒危植物三棱栎遗传多样性的RAPD分析   总被引:8,自引:2,他引:6  
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。  相似文献   

11.
Gao LZ 《Molecular ecology》2005,14(14):4287-4297
Oryza officinalis Wall. ex Watt. is an agriculturally important but seriously endangered species of wild rice. To obtain more accurate estimates of population structure for improved conservation planning of the species, genetic variability at 14 microsatellite DNA loci was examined in population samples covering most of the species' range in China. Considerable genetic variability (overall Na = 1.886, P = 62%, HO = 0.056, HE = 0.216, and HS = 0.277) was detected at the 14 loci in 442 individuals of the 18 natural populations. The evaluation of partitioning of genetic variability (FST = 0.442) suggested high genetic differentiation among the Chinese O. officinalis populations. An overall value of Nm = 0.316 suggested limited gene flow occurred among the sampled populations. Most of the populations showed heterozygote deficits in tests of Hardy-Weinberg equilibrium and significantly positive FIS values. This could be due to some inbreeding occurring in this predominantly outcrossing species. For effective in situ conservation and restoration genetics, maintenance of significant historical processes is particularly important, including high outbreeding, considerable gene flow, and large population effective sizes. The high FST values detected among populations in this study are instructive for adopting a conservation plan that includes representative populations with the greatest genetic variation for either in situ conservation management or germplasm collection expeditions.  相似文献   

12.
Kang M  Jiang M  Huang H 《Annals of botany》2005,95(7):1145-1151
BACKGROUD AND AIMS: Berchemiella wilsonii var. pubipetiolata (Rhamnaceae) is distributed in fragmented habitat patches in eastern China. It is highly endangered because of severe disturbance by anthropogenic activities. Information on genetic variation and structure is critical for developing successful conservation strategies for this species. METHODS: Allozyme variation of population genetic diversity and structure was investigated for a total of 98 individuals sampled from four extant populations using isoelectric focusing in thin-layer polyacrylamide slab gels. KEY RESULTS: Based on 20 loci scored from the nine enzymes examined, a high genetic diversity was detected at both the species and population level, while there was a loss of low frequency alleles (<0.1) in all populations. Most loci showed deviation from Hardy-Weinberg equilibrium due to excess of heterozygotes in all populations, suggesting that selection for heterozygotes has occurred in this species. The genetic diversity was mainly found within populations with a moderate genetic differentiation (F(ST) = 0.13), but the two geographically discontinuous population groups showed significant differences, with F-statistic values of 0.078 for the Zhejiang populations and 0.014 for the Anhui populations, respectively. CONCLUSIONS: It appears most likely that this species has experienced a recent decrease in population size, and genetic drift in small populations has resulted in a loss of alleles occurring at low frequency. The differentiation into two population groups reflects a population genetic consequence that has been influenced by the different land-use in the two regions. Some conservation concerns are discussed together with possible strategies for implementing in situ and ex situ conservation.  相似文献   

13.
Californian vernal pools, a patchy, island-like habitat, are endangered as a result of habitat destruction. Conservation of the remaining vernal pool habitat is essential for the persistence of several endangered species. We present the first study examining DNA-level genetic diversity within and among populations of a vernal pool plant species. We investigated genetic variation across eight populations of the US federally endangered vernal pool endemic Lasthenia conjugens (Asteraceae) using intersimple sequence repeat (ISSR) markers. Genetic diversity within the species was high (Nei's gene diversity estimate was 0.37), with moderate differentiation among populations (Bayesian F ST analog of 0.124). Using an amova analysis, we found that the majority of the genetic variation (84%) was distributed within populations. There is a significant relationship between geographical distance and pairwise genetic differentiation as measured by the Bayesian estimate θB. The alternative hypotheses of historic geological processes within the Central Valley and contemporary gene flow are discussed as explanations of the data. Because of the vulnerability of the populations, we calculated a probability of loss for rare alleles (fragments) in the populations. Calculations show that sampling only one of the eight populations for ex-situ conservation or restoration will capture approximately 54% of the sampled rare fragments. We believe that one of the sampled populations has become extinct since it was sampled. When removing this population from the above-mentioned calculations, sampling one population will capture only 41.3% of the sampled rare fragments. We recommend sampling strategies for future conservation and restoration efforts of L. conjugens.  相似文献   

14.
Guidelines designed to aid in the restoration of rare species have been previously proposed using two primary strategies to select individuals for augmentation and reintroduction: mixing progeny from different populations or separating individuals from different populations. Understanding the genetic structure and diversity of an endangered species can offer insights into conservation management strategies. We used random amplified polymorphic DNA markers to assess the genetic structure and diversity of Jacquemontia reclinata , a federally endangered species endemic to Southeastern Florida. We sampled 20 percent of total number of individuals from eight of the ten known wild populations. Across individuals high levels of polymorphic loci (94.7%) were found and larger populations had greater genetic diversity. Cluster and ordination analyses found that one population was genetically differentiated from all the others; this population grows in a unique habitat. Most genetic variation (77.5%) was found within populations, and genetic distances between populations were not explained by their geographic distances. We recommend the use of two management units in restoration programs for J. reclinata , one consisting of the genetically differentiated population and the second consisting of the other seven populations sampled.  相似文献   

15.
Anthropogenic landscape changes have greatly reduced the population size, range and migration rates of many terrestrial species. The small local effective population size of remnant populations favours loss of genetic diversity leading to reduced fitness and adaptive potential, and thus ultimately greater extinction risk. Accurately quantifying genetic diversity is therefore crucial to assessing the viability of small populations. Diversity indices are typically calculated from the multilocus genotypes of all individuals sampled within discretely defined habitat patches or larger regional extents. Importantly, discrete population approaches do not capture the clinal nature of populations genetically isolated by distance or landscape resistance. Here, we introduce spatial Genetic Diversity (sGD), a new spatially explicit tool to estimate genetic diversity based on grouping individuals into potentially overlapping genetic neighbourhoods that match the population structure, whether discrete or clinal. We compared the estimates and patterns of genetic diversity using patch or regional sampling and sGD on both simulated and empirical populations. When the population did not meet the assumptions of an island model, we found that patch and regional sampling generally overestimated local heterozygosity, inbreeding and allelic diversity. Moreover, sGD revealed fine-scale spatial heterogeneity in genetic diversity that was not evident with patch or regional sampling. These advantages should provide a more robust means to evaluate the potential for genetic factors to influence the viability of clinal populations and guide appropriate conservation plans.  相似文献   

16.
Reintroduction of populations of endangered species is a challenging task, involving a number of environmental, demographic and genetic factors. Genetic parameters of interest include historical patterns of genetic structure and gene flow. Care must be taken during reintroduction to balance the contrasting risks of inbreeding and outbreeding depression. The Mauna Loa silversword, Argyroxiphium kauense, has experienced a severe decline in population size and distribution in the recent past. Currently, three populations with a total of fewer than 1000 individuals remain. We measured genetic variation within and among the remnant populations using seven microsatellite loci. We found significant genetic variation remaining within all populations, probably related to the recent nature of the population impact, the longevity of the plants, and their apparent self-incompatibility. We also found significant genetic differentiation among the populations, reinforcing previous observations of ecological and morphological differentiation. With respect to reintroduction, the results suggest that, in the absence of additional data to the contrary, inbreeding depression may not be a substantial risk as long as propagules for the founding of new populations are adequately sampled from within each source population before additional inbreeding takes place. The results further suggest that if mixing of propagules from different source populations is not required to increase within-population genetic variation in the reintroduced populations, it may best be avoided.  相似文献   

17.
三峡库区特有种疏花水柏枝的保护遗传学研究   总被引:14,自引:2,他引:12  
采用超薄平板微型聚丙烯酰胺等电聚焦电泳方法对三峡库区特有种疏花水柏枝 (Myricarialaxiflora)的 13个自然居群和 1个人工迁地保护居群的等位酶遗传变异进行了初步研究。检测了 5个酶系统 ,得到 13个等位酶位点 ,遗传多样性及其遗传结构分析结果表明 :疏花水柏枝具有较高水平的遗传多样性 ,平均多态位点比率P =78.7% ,每位点平均等位基因数A =1.8,平均预期杂合度He=0 .317,高于中国植物特有种的平均水平 ,且群体中杂合基因型个体偏多 ;其遗传变异主要发生于居群内 ( 84.86 % ) ,居群间又存在一定的遗传分化 (Gst=0 .15 14) ,居群间平均基因流Nm =1.40 1,居群间遗传距离为 0 .0 0 2~ 0 .176 ;UPGMA聚类分析显示疏花水柏枝在三峡湖北境内的白水河—泄滩一带分为上游和下游 2个居群组 ;武汉植物园迁地保护的混合居群基本保育了其遗传多样性总水平。在分析讨论疏花水柏枝遗传多样性与其繁育系统、生境及其起源进化的关系的基础上 ,探讨了疏花水柏枝濒危的主要原因 ,推断其应为第四纪冰期影响后的古孑遗种。最后 ,在评价迁地保护成果的基础上 ,提出了今后进一步保育的策略。  相似文献   

18.
One of the most pressing issues in spatial genetics concerns sampling. Traditionally, substructure and gene flow are estimated for individuals sampled within discrete populations. Because many species may be continuously distributed across a landscape without discrete boundaries, understanding sampling issues becomes paramount. Given large-scale, geographically broad conservation efforts, researchers are looking for guidance as to the trade-offs between sampling more individuals within a population versus few individuals scattered across more populations. Here, we conducted simulations that address these issues. We first established two archetypical patterns of dispersion: (1) individuals within discrete populations, and (2) continuously distributed individuals with limited dispersal. We used genotypes generated from a spatially-explicit, individual-based program and simulated genetic structure in individuals from nine different population sizes across a landscape that either had barriers to movement (defining discrete populations) or isolation-by-distance patterns (defining continuously distributed individuals). Then, given each pattern of dispersion, we allocated samples across four different sampling strategies for each of the nine population sizes in various configurations for sampling more individuals within a population versus fewer individuals scattered across more populations. We assessed the population genetic substructure with both the population-based metric, F ST, and an individual-based metric, D PS regardless of the true pattern of dispersion to allow us to better understand the effect of incorrectly matching the metric and the distribution (e.g., F ST with continuously distributed individuals, and vice versa). We show that sampling many subpopulations (or sampling areas), thus sampling fewer individuals per subpopulation, overestimates measures of population subdivision with the population-based metric for both patterns of dispersion. In contrast, using the individual-based metric gives the opposite results: sampling too few subpopulations, and many individuals per subpopulation, produces an underestimate of the strength of isolation-by-distance. By comparing all results, we were able to suggest a strong predictive model of a chosen genetic structure metric for elucidating the sampling design trade-offs given each pattern of dispersion and configuration on the landscape.  相似文献   

19.
In dispersive species with continuous distributions, genetic differentiation between local populations is often absent or subtle and thus difficult to detect. To incorporate such subtle differentiation into management plans, it may be essential to analyse many samples from many localities using adequate numbers of high‐resolution genetic markers. Here, we evaluated the usefulness of dense locality sampling in resolving genetic population structure in the ayu (Plecoglossus altivelis), a dispersive fish important in Japanese inland fisheries. Genetic variability in, and differentiation between, ayu populations around the Japan–Ryukyu Archipelago were investigated in 4746 individuals collected from 120 localities by genotyping 12 microsatellite markers. These individuals represented the two subspecies of ayu, namely the Ryukyuan subspecies (Plecoglossus altivelis ryukyuensis) and both amphidromous and landlocked forms of the nominotypical subspecies (P. a. altivelis) along the archipelago. We successfully detected an absence of genetic differentiation within the landlocked form and subtle but significant differentiation and clear geographic patterns of genetic variation among populations of the amphidromous form, which had been considered genetically homogeneous. This suggests that dense locality sampling effectively resolves subtle differences in genetic population structure, reducing stochastic deviation in the detection of genetic differentiation and geographic patterns in local populations of this dispersive species. Resampling analyses based on empirical data sets clearly demonstrate the effectiveness of increasing the number of locality samples for stable and reliable estimations of genetic fixation indices. The genetic population structure observed within the amphidromous form provides useful information for identifying management or conservation units in ayu.  相似文献   

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