【作者】 王钦；

【导师】 马瑞君； 陈学林；

【作者基本信息】 西北师范大学 ， 植物学， 2003， 硕士

【摘要】 箭叶橐吾、黄帚橐吾和掌叶橐吾是菊科橐吾属的多年生草本植物，大量分布于青藏高原东缘。其中，箭叶橐吾和黄帚橐吾是对高寒草场危害严重的毒杂草，这两种植物不仅能以种子进行有性生殖，而且可通过地横向伸长的根状茎行克隆繁殖。近年来由于过度放牧，引起草场退化，为两种毒杂草的繁殖提供了广阔的繁殖空间，种群不断扩大，对草场危害日趋严重。本项研究采用随机扩增多态DNA(RAPD)技术，结合野外调查，全面分析这三种植物的遗传多样性水平和居群的遗传结构；探讨在不同的海拔高度中，箭叶橐吾和黄帚橐吾有性生殖和无性繁殖的权衡关系及其生态学意义，旨在揭示高山植物的居群变异和对高寒环境的适应与进化，为草原生态系统的恢复和保护，综合防除高寒草场的毒杂草提供科学依据。主要结果如下： 掌叶橐吾的三个自然居群，总计58个个体，使用17个随机引物，共扩增出201个位点。得出物种水平的多态条带百分率PPB(％)为59.20％，Nei’s的基因多样度(h)为0.1460，Shannon多样性指数(I)为0.2321。3个群体的平均多样性水平为PPB=35.99％，h=0.1081，I=0.1671。分子方差分析(AMOVA)表明，在总的遗传变异中，居群间遗传变异占27.59％，居群内占72.41％。POPGENE给出的基因分化系数(Gst)为0.2669。 箭叶橐吾的三个自然居群，总计62个个体，使用17个随机引物，共扩增出128个多态位点。得出物种水平的多态条带百分率PPB(％)为63.68％，Nei’s的基因多样度(h)为0.1688，Shannon多样性指数(I)为0.2632。3个群体的平均多样性水平为PPB=42.45％，h=0.1271，I=0.1958。分子方差分析(AMOVA)表明，在总的遗传变异中，居群间遗传变异占22.87％，居群内占77.13％。POPGENE给出的基因分化系数(Gst)为0.2400。 黄帚橐吾的五个自然居群，总计100个个体，使用17个随机引物，共扩增出132个多态位点。得出物种水平的多态条带百分率PPB(％)为65.67％，Nei’s的基因多样度(h)为0.1465，Shannon多样性指数(I)为0.2307。5个群体的平均多样性水平为PPB=32.24％，h=0.0885，I=0.1384分子方差分析(AMOVA)表明，在总的遗传变异中，居群间遗传变异占37.03％，居群内占62.97％。POPGENE给出的基因分化系数(Gst)为0.3955。 研究表明，无论是兼有两种繁殖习性的黄帚橐吾和箭叶橐吾，还是只进行有性生殖的掌叶橐吾，均有较高的遗传多样性水平。三种橐吾花序大、色泽艳丽，且开王钦青藏高原东缘案吾属三种植物的遗传多样性花期维持时间较长，有利于吸引传粉昆虫访花，促进花粉的传播。具有兼性繁殖的两种植物，它们可通过有性重组，产生供自然选择的遗传变异。 基因分化系数(必t)和分子方差(AMOVA)分析，显示三种案吾大量的遗传变异存在于居群之内，居群间遗传分化较大。针对具有兼性繁殖习性的，箭叶案吾和黄帚案吾来说，维持居群内大量遗传变异的原因是有性生殖的结果。黄帚案吾和掌叶真吾的居群间有少量的基因流(Nm)，而箭叶聚吾居群间有丰富的基因流存在。依靠风力传播的种子，是它们基因流的重要途径。使用RAPD标记，检测到了一例自然状态下存在的克隆分株，结合野外调查和移栽实验的结果，可推断在地下种间竞争激烈的高寒草甸植被中，箭叶臭吾和黄帚臭吾根状茎的生长被明显抑制，难以形成克隆分株;而退化的沙地，土质松软便没有地下其它物种的竞争，克隆生长能力增强。 本研究发现，在青藏高原东缘这样高海拔的生态环境中，植物进行克隆繁殖的器官(地下根状茎)一旦受到制约，还是以有性生殖的方式，通过产生种子的办法，尽快“逃离”目前的生境，去寻找更适宜的地区。在恶劣的自然条件下，有性生殖的各个环节如开花期、传粉昆虫数量、活动区域等都会受到多变环境的影响，而难以顺利完成，但臭吾能产生轻而小的种子，以利于风力的远距离传播，为避免因大量近交引起遗传漂变，提供了帮助。 在对箭叶真吾和黄帚案吾的防除中，应该针对其有性生殖的器官，如抽出的花梗，开放的花序等，抑制其后代的散布和种群的扩大，还要注意退化草场的生态恢复和物种保护，避免土地沙化，使聚吾的克隆生长始终受到抑制，以防止其在缺乏竞争环境中克隆繁殖得以释放居群进一步扩大，占据更为广泛的生境。更多还原

【Abstract】 Ligularia sagitta, L virgaurea, and L. przewalskii are distributed over the east of Qinghai-Tibet Plateau. Among them, L. sagitta, L. virgaurea, which have behavior of clonal reproduction, are endangering the meadow more and more seriously, the model poisonous weeds in alpine meadow. In the research, the author, by means of random amplified polymorphic DNA (RAPD) technology, studies their genetic diversity, population genetic structure, in order to provide a scientific basis for preventing meadow form retrogradation. The main esults of this research are as follows.Three natural population of L przewalskii add up to 58 individual,with 17 random primersand 201 loci were detected .At species level, the percentage of polymorphic band (PPB ) was 59.20%, Ner s gene diversity (h) was 0.1460 and Shannon index (I) was 0.2321.At population level ,the means of the three indexes were 35.99%, 0.1081 and 0.1671 c AMOVA showed that 27.59% of the genetic diversity resulted form differentiation among population with remaining 72.41% residing within population.The coefficient of gene differentiation (Gtf) generated by POPGENE was 0.2669.Three natural population of L. sagitta, add up to 62 individual , with 17 random primers, 128 polymorphic loci. At species level, the percentage of polymorphic band (PPB ) was 63.68%, Nei’ s gene diversity (h) was 0.1688 and Shannon index (I) was 0.2632.At population level ,the means of the there indexes were 42.45%,0.1271,0.1958o AMOVA showed that 22.87% of the genetic diversity resulted form differentiation among population with remaining 77.13% residing within population. The coefficient of gene differentiation (Gst) generated by POPGENE was 0.2400.Five natural population of L. virgaurea, add up to 100 individual , with 17 random primers, 132 polymorphic loci. At species level, the percentage of polymorphic band (PPB) was 65.67%, Nei’s gene diversity (h) was 0.1465 and Shannon index (I) was 0.2307.At population level ,the means of the there indexes were 32.24%,0.0885,0.1384 . AMOVA showed that 37.03%t of the genetic diversity resulted form differentiation among population with remaining 62.97% residing within population. The coefficient of gene differentiation (Gst) generated by POPGENE was 0.3955.Under natural conditions, L. sagitta and L virgaurea "s rhizomes are suppressed due to other biological competitions in the meadow, therefore they mainly zoogamy. This fact reminds us : which protecting the meadow . In order to suppress spreading and enlargement of later population, should we in order to take effective measures to sexual reproductive organs; we also need to pay more attention to ecological recovery and species protection in the degenating meadow to prevent land form further desertification , make clonal growth of Ligularia suppress all the time and prevent their from occupying more extensive habitat.更多还原