Taxonomic and population differentiation of mitochondrial diversity in Pinus banksiana and Pinus contorta

Two mitochondrial DNA polymorphisms in 741 individuals from 16 allopatric populations of Pinus banksiana Lamb. and Pinus contorta Dougl. were studied. Restriction fragments of both polymorphisms distinguished the two species qualitatively, except in a P. banksiana population whose ancestors were involved in hybridization with P. contorta. COX1-associated restriction fragments were monomorphic within species, while COX2-associated restriction fragments were highly variable in P. contorta (H(es) = 0.68). Population differentiation was substantial in P. contorta (F(st) = 0.31 among subspecies; mean F(st) = 0.66 within subspecies) and consistent with predictions for maternally inherited markers. Plant mitochondrial markers appear to be useful for the investigation of seed migration routes, hybridization and introgression, breeding zone designation, and the development of germ plasm conservation sampling strategies.