Geographic differentiation of monoterpenes from Abies procera and Abies magnifica

Cortical oleoresins from 352 Abies magnifica and A. procera trees, collected in 35 localities, were analysed for composition of their monoterpene fractions. The monoterpenes were composed primarily of -pinene, β-pinene, limonene and β-phellandrene, with camphene and 3-carene appearing only sporadically in larger amounts. Limonene, β-phellandrene, -pinene and 3-cerene were used to study the transitional populations in northern California and southern and central Oregon and the transitional-like populations in southern Sierra Nevada. The populations segregated latitudinally into three related clusters—above 44° (A.procera), between 44° and 40° (transitional), and below 40° (A.magnifica). A.magnifica from southern Sierra Nevada and A.magnifica from Mtn. Shasta differed in a number of parameters, with southern Sierra Nevada populations being chemically much closer to typical A. magnifica from central and northern Sierra Nevada. While monoterpene and morphological data did not allow a clear Interpretation of the status of the transitional and southern populations, the paleobotanical evidence favored the recent evolution over introgression. The desirability of additional studies was indicated.