Patterns of allozyme variation within and among Douglas-fir breeding zones in southwest Oregon

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Abstract
Gametophytes from wind-pollinated seeds of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) parent trees (mean 56) in each of 22 breeding zones in southwest Oregon were analyzed electrophoretically for gene frequency patterns at 27 loci. Allozyme variability levels were high, as shown by breeding-zone averages for the percentage of polymorphic loci (71.7%, 0.99 criterion), mean number of alleles per locus (2.46), and expected heterozygosity (0.178). Differences among zones in allele frequency were significant (p < 0.05) for only 2 of the 27 loci surveyed, and analysis of hierarchical population structure showed that less than 1% of genetic diversity was attributable to differences among breeding zones. Genetic disease between zones was small (.hivin.D = 0.0013) and, in general, bore no relation to geographical or environmental distance. The limited allozyme differentiation among zones contrasts strikingly with the environment-related variation in seedling quantitative traits previously reported for southwest Oregon Douglas-fir. Allozymes do not appear to be useful for mapping patterns of adaptive variation or for certifying Douglas-fir seed in this region.