【作者】 李丽丽；

【导师】 王德利；

【作者基本信息】 东北师范大学 ， 生态学， 2010， 硕士

【摘要】 植物在长期的放牧干扰下对环境的异质性会产生适应。这种适应被认为是植物在与草食动物长期的协同进化过程中采取的适应策略,主要通过表型可塑性的产生来实现。本论文应用传统生态学与分子生态学研究相结合的方法,研究羊草种群在放牧干扰下的表型可塑性及遗传多态性变化趋势,从分子水平说明羊草在放牧干扰下的适应进化机制。我们通过2008年对中国东北样带长岭、海拉尔、锡林浩特三个地区的长期放牧和无牧样地的羊草种群表型可塑性变化及生物量分配等进行研究,同时利用扩增片段长度多态性(AFLP)技术检测种群间遗传多态性及遗传距离的变化。通过数据分析,结果表明:1.在放牧干扰下,所有羊草种群叶构型指数均呈现减小趋势。长期放牧样地羊草种群的活叶数、叶长、叶宽、叶片倾角相比无牧样地显著减小,其中最明显的是叶片倾角的变化,植株生长形态上由向上直立生长,逐渐变为水平匍匐生长;羊草种群高度也表现出明显的适应变化,长岭地区放牧样地羊草种群的高度仅为8.45 cm,只有无牧种群的三分之一;羊草种群密度和根茎密度,也呈减小趋势;植株生物量相也显著降低,但是在资源分配方面,地上、地下生物量占总生物量比例并没有因为放牧影响而发生变化;双因素方差分析表明,对于羊草种群高度可塑性变化的影响,长期放牧的作用大于地理隔离的作用。2.AFLP分子标记分析结果表明,9对引物共扩增出482条带,其中385条为多态性条带,多态位点百分率达到79.87%。利用AFLP条带记录数据进行遗传多态性指标、遗传相似度、遗传距离、基因流、平均值法(UPGMA)聚类分析、分子方差分析(AMOVA),结果显示羊草种群遗传多态性虽然受到长期放牧干扰的一定影响,但这个影响并不明显,更多可能由于放牧引起的环境异质性或基因流。聚类分析结果将6个种群按地理位置分为三大类,说明地理隔离对羊草种群遗传分化及遗传多态性的影响大于长期放牧干扰影响。相关分析也进一步表明,放牧与无牧种群之间的遗传变异与种群高度、叶构型、种群密度、根茎密度等各表型可塑性指标变化不存在显著的相关性。综上所述,中国东北样带各羊草种群在长期放牧影响下产生了不同的适应性表型,通过AFLP分析表明各羊草种群之间存在着广泛的遗传变异,这种变异因地理隔离和放牧干扰所产生的变化程度不同。长期放牧对表型可塑性指标变化有显著作用,但对羊草种群遗传多态性虽有一定影响却不明显。更多还原

【Abstract】 Plants adapt to the heterogeneous resources under the long-term grazing disturbance. This adaptaion is considered a strategie in the course of the co-evolution between plant and herbivore, mainly through the production of phenotypic plasticity to achieve. We uesed the molecular ecology methods combined with traditional methods to investigate the phenotypic plasticity and genetic polymorphism of L. chinensis populations and explain the adaptation mechanisms in the molecular level under grazing disturbance.Three L. chinensis populations with 10 to 30year exclosures were selected for this study along the NECT in 2008, the phenotypic plasticity of architecture and biomass allocation pattern responding to long-term grazing was investigated. At the same time, we used amplified fragment length polymorphism (AFLP) to detect genetic variation among populations. Ous results showed:1. The indexes of leaf morphological plasticity in all populations decreased under long-term grazing, including number of live leaves, leaf length, leaf width, leaf angle, especially the leaf angle. The heights of L. chinensis populations showed significant changes affected by the grazing. The average height of grazed populations in Changling is 8.45 cm, only one-third of ungrazed populations. Long-term grazing also reduced L. chinensis population and rhizome densities. The average biomass per tiller of grazed populations were less than ungrazed ones but the biomass allocation and the ratio of above and below ground biomass had no changes. It was shown that the long-term grazing effects was greater than geographical isolation in 2-factor variance analysis.2. Nine AFLP primer pairs detected a total of 482 bands of which 385 were polymorphic, the percentage of polymorphic loci was 79.87%. Genetic diversity, genetic similarity, genetic distance, gene flow, the UPGMA cluster analysis, AMOVA were analyzed based on the pofile observed in AFLP. The results showed that genetic diversity of L. chinensis populations was affected by long-term grazing disturbance, but this effect was small, mainly caused by environmental heterogeneity after grazing or gene flow. Cluster analysis results divided the 6 populations into three categories according to geographical location, indicating that the effects of geographic isolation on genetic divergence and diversity of L. chinensis populations are greater than the long-term effects of grazing. Further analysis indicated that no significant correlation was observed between the genetic diversity and the changes in phenotypic plasticity in grazed and ungrazed populations.In conclusion L. chinensis populations in NECT offer phenotypic plasticity in the adaptation to long-term grazing. AFLP analysis was applied to a wide range of genetic diversity exists between and within the L. chinensis populations, this diversity is decided by geographical isolation and grazing. The long-term grazing on L. chinensis populations significantly affect changes in the phenotypic plasticity but small to the genetic diversity.更多还原