Allozyme variation in Piceamariana from Newfoundland: genetic diversity, population structure, and analysis of differentiation

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Abstract
Seeds from 21 populations of Piceamariana (Mill.) B.S.P. from five forest sections of the boreal forest regions in Newfoundland were analyzed for electrophoretically detectable variation in 15 proteins coded by 23 genetic loci. On the average, 38% of the loci per population were polymorphic, the number of alleles per locus was 1.44, and the expected and observed heterozygosities were 0.107 and 0.120, respectively. Contingency χ2 analysis for homogeneity of allele frequencies indicated differentiation (P < 0.05) among the 21 populations and among populations within regions. The spatial pattern of allele frequencies was correlated with geographic variables at six loci. Analysis of F-statistics showed a 6.9% excess of heterozygotes relative to Hardy–Weinberg expectations. Only 5.9% of the observed genetic variation appeared to be interpopulational, the remainder was due to differences among individuals within populations. Estimates of genetic distance among regions were only slightly larger on average (0.014) than among populations within regions (0.012). Two significant (P < 0.05) canonical discriminant functions accounted for 55% of the total variance in the 13 polymorphic loci. A complex structure of genetic variation associated with regional and altitudinal differentiation was evident, possibly the expression of underlying genetic processes such as natural selection and past migration patterns.