【摘要】 通过对克氏针茅Stipakrylovil退化系列种群分析表明 ,形态变异随退化程度而异。营养枝和生殖枝长度随退化的加重变短 ,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。等位酶分析表明 ,多态位点的百分率均在 1 0 0 % ;平均每个位点的等位基因数 (A)是 2 2 5 ,有效等位基因数 (Ae)和遗传多样度指数 (He)在种群内的分布规律是中度退化种群 >重度退化种群 >无退化种群 >轻度退化种群 ,当放牧压力达到一个阈值时 ,种群的遗传多样性有增加的趋势。克氏针茅种群间的分化系数GST为 0 2 364 ,退化系列克氏针茅种群间出现一定的分化。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 )的压力更多还原

【Abstract】 Analysis of deterioration series of Stipa kryvolii populations showed that considering the deterioration series of populations, deterioration degrees led to morphological variations. With the increase 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. The result by the means of allozyme showed that percentage of polymorphism was 100%, number of alleles of per locus was 2.25 in average, the distribution regularity of number of effective alleles of per locus (Ae) and Index of gene diversity (He) in population were that median>heavy>normal>light. If grazing stress reached a threshold, genetic diversity of population reached a transition point, with genetic diversity increased. Coefficient of gene differentiation (Gst) was 0.236 4 and differentiation among populations was at a high level in comparison with other species. 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.更多还原