Abstract: Lodgepole pine (Pinus contorta ssp. latifolia) is the most widely distributed and commercially valuable subspecies among the four recognized subspecies of P. contorta. This study explored the genetic potential of seven quantitative traits using a comprehensive 14-provenance trial that included family structure, with collections from five geographic zones across British Columbia. The analysis focused on wood specific gravity, branch characteristics (angle, diameter, and length) as well as growth parameters (height, diameter, and volume). While inter-provenance differences within zones remained generally modest at age 12, substantial variation at the family level within provenances became apparent, showing significant genetic diversity within populations. Heritability estimates showed considerable variation across both traits and geographic regions, reflecting the complex genetic basis of these characteristics. Quantitative genetic differentiation (Q_st) for all traits except branch angle indicated that natural selection rather than genetic drift drove the evolution of these traits. The lack of significant isolation-by-distance effects indicated that patterns of genetic variation were not geographically structured in a straightforward linear way. Correlation analyses among traits uncovered important evolutionary trade-offs, with specific gravity showing negative associations with growth traits and branch length, but no link to branch angle. Path analysis pinpointed branch length as a key mediating factor directly decreasing wood density while also enhancing growth performance. These results highlight the hierarchical nature of trait co-evolution, where branch angle develops independently, and branch length plays a central role in mediating covariations among other features. The comprehensive results improve our understanding of lodgepole pine’s genetic potential and offer valuable insights for breeding programs aiming to balance growth performance with wood quality objectives.

Key words: Lodgepole pine, Heritability, Quantitative trait differentiation, Correlation, Path analysis