IMPLICATIONS OF MORPHOLOGICAL AND ANATOMICAL VARIATION IN ABIES BALSAMEA AND A. LASIOCARPA (PINACEAE) FROM WESTERN CANADA

Abstract

Abies balsamea and A. lasiocarpa are closely related North American balsam firs that are generally thought to hybridize and intergrade where their ranges overlap in west‐central Alberta. To test this hypothesis, a series of collections was made from ten populations along an east‐west transect between western Saskatchewan and central British Columbia. Each tree was scored for various vegetative and cone characters. The resulting data were analyzed by Principal Components Analysis and Canonical Variates Analysis. Analyses based on vegetative data produced somewhat different results from analyses based on cone data, indicating that vegetative and sexual features of the trees respond to different selection pressures at the ecologically diverse sample sites. The combined results of analyses of vegetative and sexual data indicate that the ten populations do not represent elements of two morphologically distinct taxa. Instead, the results apparently reflect population differentation within a single, regionally variable complex in response to local selection pressures following east‐west gene flow. It is recommended that the separate species designations, A. balsamea and A. lasiocarpa, be retained since: 1) present day elements of the complex are evidently derived from separate refugia isolated by the Rocky Mountains during past glacial periods, and 2) gradual morphological differences exist between populations on each side of the Rocky Mountain crest.