【作者】 韩冰；

【导师】 许志信； 赵萌莉；

【作者基本信息】 内蒙古农业大学 ， 草业科学， 2003， 博士

【摘要】 克氏针茅为多年生密丛型旱生草本植物，是亚洲中部典型草原的主要建群种。因其能够适应干旱的生态环境，分布范围极广。本文从表型性状和遗传多样性等方面探讨了内蒙古不同分布地区及不同退化系列克氏针茅种群的变异和生态分化，研究结果如下： 不同地理种群克氏针茅的生殖枝和营养枝长度及种子形态等7个表型性状存在着丰富的变异，不同的表型性状其变异幅度和变异来源各不相同，即各表型性状受环境影响改变程度的差异不同，其中营养枝长、生殖枝长、千粒重、颖果长、芒柱长具有随降水量递减而变小、变短的趋势；而颖果直径表现为随着降雨量的递减有逐渐增加的趋势。7个表型性状反应出的变异中大约有35.10％的变异来自种群间，其余大部分变异(64.90％)来自种群内部。 采用RAPD方法对不同地理种群的研究表明，16个引物共扩增出129个位点，其中多态位点128个，多态位点百分率是99.22％，说明克氏针茅具有较高的遗传多样性。其中荒漠草原带的种群的遗传多样性(0.3640)高于典型草原带(0.3306)。聚类分析表明，相似的生态条件及直线地理距离较近的种群具有优先聚类的趋势。Shannon指数估测有29.25％的遗传变异存在于种群间，种群间的遗传分化较高。 退化系列种群的形态变异随退化程度而异，营养枝和生殖枝长度随着退化的加重枝条长度变短，中、小株丛减少，生殖分配减少，生殖枝数量减少。重度退化种群，植株小型化明显。 等位酶和RAPD标记分析退化系列种群，其遗传多样性随退化程度加重有降低的趋势，但与退化程度无明显的线性相关。当放牧压力达到一个阈值时种群的遗传多样性有一个跃变点，遗传多样性又有增加的趋势。克氏针茅退化种群，生产力衰退明显但遗传多样性并未丧失，反而形成了一个相对稳定的遗传结构适应环境(放牧)的压力。 等位酶和RAPD两种方法在退化系列种群中检测的遗传多样性变化模式不同，等位酶分析结果是中度退化种群＞重度退化种群＞无退化种群＞轻度退化种群；RAPD分析结果是无退化种群＞轻度退化种群＞重度退化种群＞中度退化种群。二者聚类顺序不同可以进一步说明，放牧压力作用使种群在等位酶的基因位点与全基因组序列的变异模式不同。 克氏针茅是经过长期的进化和选择保留下来的物种，具有丰富的遗传多样性和强的进化趋势。不同的地理条件和放牧利用压力对基因流和基因频率发生影响，决定了分子变异在时空上的分布，是克氏针茅种群发生分化的最根本原因。不同退化系列，克氏针茅种群虽发生了遗传分化，遗传多样性略有降低但仍维持较高的水平，且与正常草地间有基因流，只要采取合理的草地利用措施，减轻放牧压力，退化草地即可恢复，若采取人工补播正常种群种子，将会加快退化种群的恢复进程。更多还原

【Abstract】 Stipa krylovii is a major component of typical steppe vegetation. It is a perennial, thicket, xerophytic bunch grass, with a high drought resistance. It distributes in a large area. Based on the morphological characteristics and genetic diversity, population variation and ecological differentiation of S. krylovii under different geographical conditions and deterioration stages in Inner Mongolia steppe were studied. The results were as follows:Seven morphological traits of S. krylovii (reproductive tiller length, vegetative tiller length, seed shape, etc.) showed abundant variations. Range and sources of variations were different. Variation degrees of the morphological traits were different in corresponding to environmental conditions. Reproductive tiller length, vegetative tiller length, thousand kernel weight, caryopsis length and awn length were shorter and smaller, with decreasing rainfall, while caryopsis diameter was bigger. 35.10% of variation came from inter-population, while the other (64.90%) was within population.Random amplified polymorphic DNA (RAPD) analysis demonstrated that 16 random primers produced 129 loci, obtaining 128 polymorphic loci in 7 populations from different geographical locations. The total percentage of polymorphism was 99.22%, which showed S. krylovii had abundant genetic diversity. Genetic diversity level of population in desert steppe (0.3640) was higher than that in typical steppe (0.3306). Using Un-weighted Pair-group method, the population living in similar ecological conditions and with close geographical distance clustered first. By Shannon index evaluation, 29.25% of genetic variation was between populations and the differentiation among populations was at a high level, in comparison with other species, such as S. grandis.Considering the deterioration series of populations, deterioration degrees led to morphological variations. With the increasing of grassland deterioration, vegetative tiller length and reproductive tiller length became shorter. Medium sized bunch, small sized bunch, reproductive tiller percentage, reproductive tiller number were reduced. Plant minimization was apparent in heavy deteriorated populations.Deterioration series of populations were analyzed by the means of allozyme and RAPD. The results showed that as the deterioration of grassland became heavier, genetic diversity would drop, but there was no distinct linear correlation between genetic diversity and deterioration degree. If grazing stress reached a threshold, genetic diversity of populationemerged a transition point, with genetic diversity increased. Although productivity of deteriorated population diminished obviously, genetic diversity did not totally lost. In contrast, a relatively steady genetic structure was formed to adapt environmental (grazing) stress.Analyses on allozyme and RAPD showed changes of genetic diversity had different models. The pattern for allozyme was that: rnedian>heavy>normal>light, while the pattern for RAPD indicated that: normal>light>heavy>median. The difference of two cluster diagraphs also explained the similar trend. Affected by the grazing stress, patterns of variation in coding allozyme gene-locus and genome were different.S. krylovii has abundant genetic diversity and strong evolutionary tendency, it has been undergoing a long-term evolution and the plant has been retained under natural selection. The most fundamental reason for population differentiation is that, different environmental conditions and grazing stress exert influences upon gene pool and gene rate, which can decide distribution of molecular variation in space and time. The study of different deteriorated grasslands showed, although occurring genetic differentiation and reduced genetic diversity, biodiversity in deteriorated population can still maintain a high level. Additionally, it had gene exchanges with normal populations. The deteriorated grassland can restore its vegetation as normal if rational management was adopted.更多还原