Population differentiation of the lodgepole pine (Pinus contorta) and jack pine (Pinus banksiana) complex in Alberta: growth, survival, and responses to climate

Abstract

Growth and survival of 33 populations from a species complex involving interior lodgepole pine ( Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) and jack pine ( Pinus banksiana Lamb.) and their natural hybrids in Alberta were evaluated at ages 5, 10, and 15 years in eight test sites across Alberta. We determined population differentiations by estimating Mahalanobis distances between populations from the canonical discriminant analysis of the total variability and by calculating dissimilarity indexes between populations from the quadratic regression of overall growth and survival on the overall climate. The grouping of the populations based on the Mahalanobis distances showed that most jack pine populations could be separated from lodgepole and hybrid populations, but no further subdivision was possible to distinguish lodgepole from hybrid populations. This clustering pattern was remarkably similar to the grouping based on molecular markers as shown in our earlier study. This pattern of grouping is best explained by a clear elevational demarcation between jack pine at low elevations and lodgepole pine and hybrids at midrange and high elevations. The grouping of the populations based on the dissimilarity indexes revealed a somewhat contrasting pattern; most lodgepole pine populations were in one group, whereas jack pine and hybrid populations were mixed up in the other group. The two contrasting patterns of grouping suggest that nonclimatic factors such as edaphic preference and habitat disturbances are also important in determining population distributions and niche spaces in the lodgepole – jack pine complex.