Monoterpene and morphological variation and hybridization of Pinus contorta and P. banksiana in Alberta

Abstract

Five xylem oleoresin monoterpenes and 17 morphological characters of trees in four pine stands in Alberta were measured to delineate pure lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) from jack pine (P. banksiana Lamb.) in a region where hybridization commonly has been reported. Multivariate analysis determined α-pinene, β-phellandrene, and needle length best separated the taxa. The monoterpene composition of two putative hybrid stands at Onoway and Devon closely resembled that of jack pine. Analysis of the four major monoterpenes in an additional 10 stands allowed the identification of a transition zone between jack pine and lodgepole pine stands, which occurred farther west than previously reported and contained stands of highly variable monoterpene types. Trees in this region morphologically resembled lodgepole pine. The presence of variant monoterpene types in Front Range lodgepole pine stands and their absence from the Cypress Hills provide evidence for introgression of jack pine into lodgepole pine. No evidence of gene flow from lodgepole pine to jack pine was found. The two putative hybrid stands at Onoway and Devon probably consisted mostly of jack pine, with a small complement of hybrids.