Premoli A C
Laboratorio Ecotono, Centro Regional Universitario Bariloche, Universidad Nacional del Comahue, Quintral 1250, 8400 Bariloche, Argentina.
J Hered. 2003 May-Jun;94(3):218-26. doi: 10.1093/jhered/esg052.
Variable physical conditions along elevational gradients strongly influence patterns of genetic differentiation in tree species. Here, the hypothesis is tested that different growth forms of Nothofagus pumilio, which characterizes the subalpine forests in the southern Andes, will display continuous genetic variation with elevation. At each of four elevational strips in three different mountain ranges, fresh leaf tissue was sampled from 30 randomly selected individuals to be analyzed by protein electrophoresis. Allelic frequencies were used to test for heterogeneity across populations and to classify populations into different elevational strips by discriminant analysis. The degree of population divergence was estimated by F(ST). Clinical variation on within-population genetic characteristics was analyzed by linear regressions against elevation. Seven enzyme systems coded for 14 putative isozyme loci, 57% of which were polymorphic in at least one population. Allele frequencies significantly varied with elevation and discriminant analysis separated populations at different elevational strips. Among-population divergence within any mountain range was small, but greater than among different mountain ranges. Overall, low-elevation populations were more variable than high-elevation populations, and regression analyses suggested continuous variation in populations of N. pumilio 100 m apart. Marked stepwise phenological differences on mountain slopes are most probably responsible for the isolation of nearby populations.
沿海拔梯度变化的自然条件强烈影响树种的遗传分化模式。在此，对以下假说进行了检验：构成安第斯山脉南部亚高山森林特征的矮假山毛榉的不同生长形式，将随海拔呈现连续的遗传变异。在三个不同山脉的四个海拔带中，从30个随机选取的个体采集新鲜叶片组织，通过蛋白质电泳进行分析。等位基因频率用于检验种群间的异质性，并通过判别分析将种群划分为不同的海拔带。通过F(ST)估计种群分化程度。针对海拔进行线性回归分析种群内遗传特征的渐变。七个酶系统编码14个假定的同工酶位点，其中57%在至少一个种群中具有多态性。等位基因频率随海拔显著变化，判别分析将不同海拔带的种群区分开来。任何一个山脉内种群间的分化较小，但大于不同山脉间的分化。总体而言，低海拔种群比高海拔种群变异更大，回归分析表明相隔100米的矮假山毛榉种群存在连续变异。山坡上明显的逐步物候差异很可能是导致相邻种群隔离的原因。
