In older literature, the Dusky Shrew was classified as Sorex obscurus, but the name Sorex monticolus has priority over Sorex obscurus. Because of its large distributional area and the occurrence of a number of isolated island populations, Sorex monticolus demonstrates considerable geographic variation in size and fur colour. In her recent taxonomic revision, Lois Alexander recognized 14 subspecies; 8 occur in British Columbia.
Sorex monticolus calvertensis Cowan is a weakly defined, insular subspecies confined to two widely separated islands on the north coast: Banks and Calvert. This race is larger than the mainland subspecies Sorex monticolus longicaudus, but it is very similar in skull size to S. m. elassodon and only differs in its paler colour. Genetic studies are required to evaluate the validity of this subspecies.
Sorex monticolus elassodon Osgood is an insular race associated with islands of the Alexander Archipelago in southeastern Alaska, the Queen Charlotte Islands (excluding Kunghit Island), and Porcher and Dewdney islands. It is smaller than S.m. prevostenis from Kunghit Island and the mainland race S.m. longicaudus.
Sorex monticolus insularis Cowan is an insular race confined to Reginald, Athlone (formerly Smythe) and Townsend islands in the Bardswell Group. Compared to S.m. longicaudus, the race found on the adjacent mainland, this subspecies is larger in some skull measurements but smaller in others.
Sorex monticolus isolatus Jackson is an insular race found on Vancouver Island, Denman Island, Cox Island in the Scott Islands, and a number of islands off the west coast of Vancouver Island. It is smaller than S.m. setosus, the subspecies found on the southern mainland and islands adjacent to the mainland.
Sorex monticolus longicaudus Merriam ranges from Taku, Alaska to Rivers Inlet on the coastal mainland. Eastern limits of the range are on the eastern slopes of the Coast Mountains. This subspecies also occurs on a number of islands: Campania, Campbell, Chatfield, Dufferin, Horsfall, the Hunter Group, West Kinahan, Pitt, Princess Royal, Spider, Swindle and Yeo. It is larger than S.m. setosus, the coastal subspecies to the south.
Sorex monticolus obscurus Merriam is a widespread subspecies that ranges from Alaska throughout the Cordillera of western Canada and the United States. In British Columbia, it is found across the entire mainland east of the Coast Mountains and Cascade Range.
Sorex monticolus prevostensis Osgood is confined to Kunghit Island (formerly Prevost) in the Queen Charlotte Islands. It is larger than S.m. elassodon, the other race found on the Queen Charlotte Islands.
Sorex monticolus setosus Elliot inhabits the southern coastal mainland from Rivers Inlet to Washington State. Eastern limits are the Coastal mountains and western slopes of the Cascade Range as far east as Manning Provincial Park. It also occurs on a number of coastal islands including Bowen, Cortes, Goose, Hecate, Marina, Maurelle, Quadra, Sonora, Stuart and Texada. The Texada Island population was originally classified as S.m. mixtus, but this taxon is no longer considered valid.
|