【作者】 陆建英；

【导师】 马瑞君；

【作者基本信息】 西北师范大学 ， 植物学， 2007， 硕士

【摘要】 珠芽蓼（Polygonum viviparum）和鹅绒委陵菜（Potentilla anserine）是青藏高原东缘广泛分布的两种克隆植物,它们都具有有性和无性两种生殖方式。不同的是,珠芽蓼的无性繁殖是通过珠芽和地下根状茎来完成的,而鹅绒委陵菜则是以地上匍匐茎为主要的克隆器官。珠芽蓼是在世界范围内广泛分布的物种从温带到北极海岸,从海拔较低的美洲、欧洲到地球第三极的青藏高原乃至世界屋脊的喜玛拉雅山都有它的分布。鹅绒委陵菜在我国分布也很广,可作牧草。鹅绒委陵菜对异质性资源有较强的可塑性,是嵩草草甸原生植被破坏或草甸退化后出现的优势种或先锋种之一。本研究应用随机扩增多态DNA（RAPD）对珠芽蓼和鹅绒委陵菜的遗传多样性和克隆结构及其与海拔因子的关系进行分析研究,从而揭示克隆植物的繁殖和分布特点,也为进一步研究草场的退化机制和恢复与重建提供理论依据。用13条随机引物对珠芽蓼7个种群的140个个体进行扩增,共检测到117个位点,其中多态性位点84个,多态位点比率（PPL）为71.79%。将在各扩增位点的RAPD谱带完全相同的个体视为同一克隆（即基因型相同）,结果鉴定出43个基因型。克隆多样性结果显示,珠芽蓼种群克隆多样性水平较高,Simpson指数平均为0.639,基因型比率PD平均为0.307。运用POPGENE32软件分析表明,珠芽蓼具有较高的遗传多样性;种群总的Nei’s基因多样性为0.2891,总的Shannon信息多样性指数为0.4207,但各种群内遗传多样性水平则较低,种群内平均Nei’s基因多样性为0.1227,平均Shannon信息指数为0.1804;种群间基因分化系数G_ST=0.5753,基因流Nm=0.3691,种群间基因分化大于种群内基因分化,种群的基因交流很少。贝叶斯分析求出θ^B（Hickory）=0.6023,同种群间基因分化系数G_ST（0.5753）较为接近。AMOVA分析显示,在全部变异中,66.59%的遗传变异存在于种群间,33.41%存在于种群内。相关性分析显示,种群的遗传多样性、克隆多样性与海拔均没有显著的相关性。用13条随机引物对鹅绒委陵菜6个种群120个个体进行扩增,共扩增到132条带,多态性条带为117,多态位点比率（PPL）为88.64%,鉴定出68个基因型。鹅绒委陵菜克隆多样性比珠芽蓼高,Simpson指数平均为0.875,PD平均为0.527。同样,采用POPGENE32软件分析表明,鹅绒委陵菜具有高的遗传多样性;种群总的Nei’s基因多样性为0.3180,总的Shannon信息多样性指数为0.4732,但各种群内部遗传多样性水平则较低,种群内平均Nei’s基因多样性为0.1663,平均Shannon信息指数为0.2491;基因分化系数G_ST=0.4770,基因流Nm=0.5482,种群内基因分化稍大于种群间基因分化,种群的基因交流比较少。贝叶斯分析得出,θ^B（Hickory）=0.4908,同种群间基因分化系数G_ST（0.4770）较为接近。AMOVA分析显示,在全部变异中,50.82%的遗传变异存在于种群间,49.18%的遗传变异存在于种群内。相关性分析显示,种群的遗传多样性、克隆多样性与海拔均没有显著的相关性,但与种群植被盖度有显著的相关性（r=0.8630）。结果显示,两种克隆植物虽然克隆器官不同,但种群都具有较高的遗传多样性,且几乎所有的种群都是多克隆种群。由于长期以来,人们都很少观察到作为植物体雏形的胚的发育形成甚至成熟的胚囊,因此珠芽蓼被认为是很少进行有性繁殖的物种。本研究结果则表明,青藏高原东缘分布的珠芽蓼是具有一定水平的有性繁殖的。至于具体影响有性与无性繁殖比例分配的因素,还需做进一步研究。鹅绒委陵菜则具有高的遗传变异,这可能与种苗补充有关。植物根据生境的不同来适时调整繁殖策略,这也是植物赖以生存的生长规律。另外,两种克隆植物种群内都有不同程度的克隆间镶嵌现象,这与它们的克隆构型密切有关。从种群内克隆的空间分布情况看,珠芽蓼克隆种群的构型为混合型,鹅绒委陵菜则是游击型。这种混合型和游击型的克隆生长空间格局形成了基株之间的镶嵌分布,使得克隆植物具有最大限度的利用资源的能力,在生存竞争中能使种群得以保存和发展。青藏高原东缘高寒草场上牧草品质优良,营养丰富,是发展草地畜牧业的重要物质基础。近几十年,随着人类经济活动的不断加强,以不可持续的方式滥用自然资源,大面积森林被滥砍滥伐、草原过度放牧、草场不断退化,导致适口性差的杂类草种类和丰富度增加,适口性好的植物的丰富度减少,草地的生产力下降,草地资源的可利用水平也在下降,草地的某些生态功能发生减退甚至消失。鹅绒委陵菜能够在竞争异常激烈的环境条件下,扩展种群大小,迅速占据广泛的生境范围,最终成为嵩草草甸原生植被破坏或草甸退化后出现的优势种或先锋种,自有其一套独特的适应对策。为了尽可能减少杂类草种类,增加优质牧草数量,提高草地质量,今后我们还需进一步研究克隆杂草的生长繁殖策略及具体影响因子,为草原生态系统的恢复和保护提供必要的科学依据。更多还原

【Abstract】 Polygonum viviparum and Potentilla anserine are two clonal plants, which are widely distributed in the east of Qinghai-Tibet Plateau. Both the plants have clonal reproduction and seed reproduction, differing in depended on the rhizome under ground and bulbils for Polygonum viviparum and stolons for Potentilla anserine in clonal reproduction.Polygonum viviparum is distributed widely from temperature tone to arctic ocean, from American, Europe with low altitude to Qinghai -Tibet plateau of China and Himalayas. Potentilla anserine is also distributed widely in China and is a kind of pastures. Potentilla anserine have vigorous capacity of using different environment, so it has became one of dominant species in the degenerating meadow. The genetic diversity, clonal structure and relation to the altitude among seven populations of Potentilla viviparum and six populations of Potentilla anserine were analyzed by random amplified polymorphic DNA （RAPD） technique. The results suggest that progenitive character and distribution of clonal plant, and providing the foundation for studying mechanism of grassland deterioration, resume and regenerate it.13 random primers were selected out for the amplification of Polygonum viviparum and 117 repetitive loci with 84 polymorphic loci were generated. The total average percentage of polymorphic loci （PPL）was 71.79%, while that of population was only 32.60%. Meanwhile, we could also differentiate 43 RAPD genotypes among the 140 plants sampled from 7 populations. The mean of Simpson’s index D was 0.639, and the mean of PD was 0.307, indicating that it was higher slightly than the mean of Ellstrand etal. （D=0.62, PD=0.17） .The genetic diversity of Polygonum viviparum was higher with an average Nei’s gene diversity of 0.2891 and that of the Shannon’s information index of 0.4207. In contrast, the genetic diversity within each population was low, with an average Nei’s gene diversity of 0.1227 and an average Shannon’s information index 0.1804. That the gene flow estimated by G_ST was only 0.3691, indicating low exchange among populations of Polygonum viviparum. Bayesian approaches showed the estimate forθ^B was 0.6023 and its 95% credible interval is [0.5539, 0.6454]. The G_ST values estimated by Nei index are 0.5753, very close to theθ^B estimate. AMOVA also demonstrated 66.59% of genetic variance among population, 33.41% of that within populations. The correlation analysis showed that the genetic diversity and clonal diversity within populations was not significantly related with the altitude.13 random primers were selected out for the amplification of Potentilla anserine and 132 repetitive loci with 117 polymorphic loci were produced. Total PPL was 88.64%, while that of population was only 49.12%. We could also differentiate 68 RAPD genotypes among 120 plants. The clonal diversity was high in the populations, the mean of Simpson’s index D was 0.875, PD was 0.567. The genetic diversity of Potentilla anserine was high, with an average Nei’s gene diversity of 0.3180 and an average Shannon’s information index of 0.4732. In contrast, the genetic diversity within each population was low, with an average Nei’s gene diversity of 0.1663 and an average Shannon’s information index 0.2491. Bayesian approaches showed the estimate forθ^B was 0.4908 and its 95% credible interval is [0.4522, 0.5293]. The G_ST values estimated by Nei index are 0.4770, very close to theθ^B estimate, indicating less differentiation between populations than within populations. In addition, less gene exchange between populations （Nm—0.5482） was detected. AMOVA also demonstrated that genetic variance 49.18% existing within population, 50.82% among populations. The correlation analysis showed that the genetic diversity clonal diversity within populations was not significantly related with the altitude. However, the genetic diversity within populations was significantly positively related with the coverage （r= 0.8630）.Clonal organ of two plant is different, but genetic diversity of populations is high, and populations are polyclonal. Because embryonal development and few megaspores were observed, Polygonum viviparum has hardly seed reproduction. However, this study results indicate Polygonum viviparum distributed in the east of Qinghai-Tibet Plateau have a little sexual reproduction, and the ratio of asexual and sexual reproduction need be studied further. High genetic variation of Potentilla anserine possibly related seed recruitment. Plant adjust reproduction strategy timely according to their habitat, which is dependent grow rule of plant. The analysis of clonal structure demonstrated that the mosaic among two clonal plant clones was clear, suggesting that this is probably because of their clonal architecture. Polygonum viviparum is transitional type between guerilla and phalanx and Potentilla anserine is guerilla clonal structure. This confirmed different clones （genotypes） have different growth potential, fitness and competition.Alpine meadow grassland is widely distributed in the central-eastern part of the Qinghai-Tibet Plateau and its surrounding mountain region, where the pasture is well on quantity. In recently years, the source are present the problem of ecology environment on vegetation degrading, land desertification process expanding rapidly and wetland ecology degrading. From light grazing to over-grazing, the dominant shrub and graminoid species were replaced by typical forbs and the index of rangeland quality decreased. Long-term heavy grazing plays an important role on alpine rangeland degradation in Qinghai-Tibet Plateau. Potentilla anserine is capable of expand grow range rapidly by clonal organ （stolons） and becomed the dominant species of Kobresia humilis meadow. For the future, we need to study reproduction strategy of clonal weed further and provide the foundation for studying mechanism of grassland deterioration, resume and regenerate it.更多还原