Genetic architecture and adaptive landscape of interior lodgepole pine (Pinus contorta ssp latifolia) in Canada

The genetic architecture and adaptive landscape of interior lodgepole pine (Pinus contorta ssp. latifolia Engelm. ex S. Wats.) in Canada were investigated in a provenance-family plantation located in central British Columbia. Fifty-three natural populations were sampled from three geographic regions covering the entire Canadian range, and their performance in growth and survival was recorded periodically over 20 years. Test results indicate that,genetic variation among regions and among populations within regions was highly significant in all the traits investigated and accounted for, respectively, 53% and 41% of the total genetic variation in growth and 41% and 54% in survival. Within-population variation was also significant in growth but not in survival. Interior lodgepole pine in the central region demonstrated less genetic variation than in the northern and southern regions at both the population and family levels. In addition, the proportion of genetic variation associated with population was lower in the central region than in the other regions. Population differentiation in both growth and survival showed discernible elevational and geographic patterns. Regression models describing these adaptive patterns accounted for more than 80% of the among-population variation, and their veracity was verified with independent data. Populations of northern, coastal-interior transition, and high-elevation origin tended to have smaller trees with higher mortality. However, the patterns were not linear but differed in slope and (or) direction among regions. The adaptedness of populations tended to decrease as they were farther away from their origin, with a few exceptions displaying broad adaptation across more than 3 degrees of latitude. As the test proceeded, population differentiation became more evident and adaptive dines became steeper. Some practical implications of these findings have been discussed.