Generation-dependent patterns of variation and population differentiation in Abies amabilis and A. lasiocarpa (Pinaceae) from north-coastal British Columbia
To investigate generation-dependent patterns of variation and differentiation in populations of Abies amabilis and A. lasiocarpa from north-coastal British Columbia, seven leaf variables were analyzed by multivariate methods. Principal-components analysis of leaf data from sexually immature trees of Abies amabilis and A. lasiocarpa indicated no evidence of hybridization between these two species, even on a disturbed site where sexually mature individuals of both species are sympatric. Regression analysis indicated that a change with altitude occurs in A. amabilis. Evidence of population differentiation in immature individuals of both species was demonstrated by canonical variates analysis: (1) in A. amabilis a canyon bottom population appeared distinctive; (2) in A. lasiocarpa population differentiation is related to latitude. Variation patterns in both species suggest that geographic distance and taxonomic distance between populations are independent. Such patterns would be predicted if selection were a more important determinant of population differentiation than gene flow. There is some indication that mature populations are more variable than immature.