Patterns of allozyme variation in tamarack (Larix laricina (Du Roi) K. Koch) from northern Ontario

Roots from approximately 30 trees from each of 44 populations across the range of tamarack (Larix laricina (Du Roi) K. Koch) in northern Ontario were analyzed electrophoretically for allozymic variation in 14 enzyme systems coded by 20 loci. A low level of variability was found in this conifer. On average, 22.7 - 28.8% of the loci per population were polymorphic depending on the criterion of polymorphism, with a mean of 2.60 alleles per polymorphic locus. Expected and observed heterozygosity per population were 0.091 and 0.087, respectively. G-tests for allelic homogeneity among populations indicated genetic heterogeneity (p < 0.05) at four loci. Approximately 4% of the total genetic diversity resided among populations. The mean genetic distance over all pairs of tamarack was 0.0045. Genetic distance was significantly related to geographic distance, and the latter accounted for 9% of the variation in genetic distance. Seven significant (p < 0.05) canonical discriminant functions accounted for 67.4% of the total variation at the polymorphic loci. Genetic variation in tamarack appeared to be affected by the environmental variables. An evolutionary bottleneck might be responsible for the low variability. The relatively short colonization since glaciation seemed the most likely factors causing the relatively low differentiation among populations