Phenotypic variation in Yukon populations of subalpine fir

Abstract

To clarify the taxonomy of subalpine fir (Abies lasiocarpa (Hook.) Nutt.) and its relationship to balsam fir (Abies balsamea (L.) Mill.), populations from Washington to Yukon Territory and east to northern Ontario were compared on the basis of cone and needle morphology. Variation at the northern extreme of subalpine fir's range was expressed primarily within populations and appears to have arisen from selection owing to local environmental pressures. Multivariate analyses indicated geographic differentiation of coastal and interior subalpine fir populations and an affinity between northern and interior subalpine fir populations. Palynological data as well as similarities between northern and southern interior populations suggest a common Rocky Mountain refugium for the northern and interior populations. These results, together with earlier studies, justify varietal status for subalpine fir populations occurring east of the Coast and Cascade mountains of Washington and British Columbia and extending eastward to the Rocky Mountain crest. The new name for this interior variety is Abies lasiocarpa (Hook.) Nutt. var bifolia (Murray) Palmer & Parker. Balsam fir populations were indistinguishable from interior subalpine fir populations on the basis of needle morphology but well differentiated from these and coastal populations in cone morphology, supporting continued recognition of these firs as separate species. Key words: Abies balsamea, Abies lasiocarpa, Abies lasiocarpa var. bifolia, balsam fir, phenotypic variation, subalpine fir, taxonomy.