Some geographic variations in Picea sitchensis and their ecologic interpretation

Abstract

Mass collections of Picea sitchensis, and hybrids, extending from Haines, Alaska, to northern California have been studied with respect to morphology of the ovuliferous cones, twigs, and needles. The Pleistocene history of the species has been reviewed. A north–south gradient occurs in size of cone, length–width ratios of cone scales, sterigma angle, and phyllotaxy. The gradient is probably clinal and appears unaffected by the northerly three-fourths of the species range being in glaciated territory where Pleistocene survival, on nunataks, is suggested by the data. Collections along two sections of the Skeena River in British Columbia are interpreted as hybrid P. sitchensis × P. glauca populations backcrossed with the nearest one of the two parents, i.e., with P. sitchensis near the coast and P. glauca farther inland. Insular populations tend to show less variability in length–width ratios of the ovuliferous scales than do mainland populations.