Kendrick L. Marr, Richard J. Hebda, William H. MacKenzie
The distribution of northern British Columbia alpine plants is poorly documented. To improve our understanding of the flora of this vast, remote region, we collected more than 11 000 specimens from 65 mountains during 2002–2011. Most of these locations had not been visited by botanists. Of the more than 400 species we have collected, two are new to the province, others represent significant range extensions. Twelve species share elements of a disjunct distribution that has apparently not been previously recognized and consists of three regions: (1) northwestern North America; (2) Beartooth Plateau; and (3) northern Colorado. These 12 species appear to be absent from the extensive areas of suitable habitat that occur in the intervening areas. The most reasonable explanation for this pattern is that these species, adapted to arctic–alpine tundra conditions, migrated throughout western North America during the Pleistocene, a time when suitable habitat was much more widespread than now, and subsequently went extinct in many areas as the climate warmed during the Holocene.