Genetic diversity within and among six subpopulations of Larix decidua Mill. from two altitudinal transects of Swiss Alps was investigated using 6 enzyme systems coding for 8 loci. Globally, the mean proportion of polymorphic loci was 22.9%, the average number of alleles per locus was 1.3, and the mean expected heterozygosity was 0.095. Only 5.8% of the genetic variation resided among populations. The mean genetic distance was 0.006. Several significant differences of gene frequencies were found between different age classes. Positive values of the species mean fixation index observed in this study suggested a considerable deficit of heterozygotes in the populations of L. decidua of Swiss Alps. At one of the sites (Arpette), the highest subpopulation in elevation gave the lowest level of genetic diversity (as evidenced by the lowest proportion of polymorphic loci and the lowest mean expected heterozygosity) and the largest value of genetic distance when compared to other subpopulations. The genetic differences between the highest subpopulation and the other ones suggest that the founder effect may be an important factor influencing genetic differentiation of L. decidua populations at Arpette transect.
赵桂仿1 Francois FELBER2 Philippe KUPFER2
（1. 西北大学生命科学学院，秦岭生物多样性研究中心，西安710069；2.Botanical lnstitute,Neuchatel Unixersiy,Emile-Arpand 11,CH-2007,Neycgatel,Switzerland)
摘要：应用等位酶分析技术,沿两个海拔梯度在瑞士阿尔卑斯山研究了欧洲落叶松(Larix decidua Mill.)居群内和居群间的遗传多态性。结果表明,多态性位点的比例为22.9%,平均每个位点的等位基因数为 1.3,平均期望杂合度为 0.095,遗传变异的5.8% 存在于居群之间,平均遗传距离为 0.006。几个有统计意义的基因频率差别在不同树龄类被发现。正的繁育系数值表明在瑞士阿尔卑斯山欧洲落叶松居群有相当的杂合体缺乏。在阿尔拜特(Arpette),海拔最高的亚居群与其他亚居群相比较显示最低的遗传多态性(如显示最低的多态性位点比例和最低的平均期望杂合度)和最大的遗传距离值。在最高亚居群和其他亚居群间的遗传差别暗示奠基者效应可能是影响这个定样场所欧洲落叶松居群遗传分化的主要因素。