Genetic and morphological relationships between blue spruce, Picea pungens, and Engelmann spruce, Picea engelmannii, in the Colorado Front Range

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Abstract
Nine morphological characters and one enzyme polymorphism were used in a study of hybridization of blue and Engelmann spruce in the Front Range of Colorado. Eighty-eight trees were studied in one pure Engelmann spruce population, one pure blue spruce population, and three sympatric populations along an elevational transect. The morphological data were summarized with principal components analysis, but no clusters were evident in the projections. A protein polymorphism indicated a predominance of different alleles in the two species, and none of the most common expected (hybrid) heterozygotes were seen. The protein data allowed unambiguous assignment of individuals to separate groups, and subsequently discriminant analysis was performed. The species could be significantly resolved by discriminant analysis of the morphological traits, but a small degree of overlap between species remained.
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