Isozyme variation in balsam poplar along a latitudinal transect in northwestern Ontario

Abstract

Isozyme characteristics were examined for eight enzyme systems in five 50-tree populations of balsam poplar (Populusbalsamifera L.) collected at longitude 90°W, from latitudes 45 to 55°N. Fifty-four percent of the trees were polymorphic at one or more loci, and 8 of the 17 loci examined were polymorphic in one or more populations. Average heterozygosity was low (0.037) and varied little among populations (0.025–0.043). No significant departure of multilocus genotypic proportions from those expected under random mating was observed. Genetic distances and F-statistics indicated that there is little genetic differentiation among populations in terms of the observed enzyme systems.