Saxifraga rivularis subsp. arctolitoralis (Jurtz. & V.V. Petrovsky) M.H. Jorg . & Elven

Gillespie, Lynn J., Saarela, Jeffery M., Sokoloff, Paul C. & Bull, Roger D., 2015, New vascular plant records for the Canadian Arctic Archipelago, PhytoKeys 52, pp. 23-79 : 57

Saxifraga rivularis subsp. arctolitoralis (Jurtz. & V.V. Petrovsky) M.H. Jorg. & Elven

Common name.

Alpine brook saxifrage

Distribution.

Arctic amphi-Beringia-North America

Comments.

This collection (det. R. Elven and L.J. Gillespie) represents the first record of Saxifraga rivularis L. as currently circumscribed from the western CAA and the first record of Saxifraga rivularis subsp. arctolitoralis from the CAA. Porsild (1957) and Porsild and Cody (1980) previously treated the species in a broader sense and included plants now treated under Saxifraga hyperborea R.Br., a circum-Arctic species (all collections of Saxifraga rivularis s.l. mapped by them from the western Arctic Islands are now considered Saxifraga hyperborea ). As treated by Aiken et al. (2007), Saxifraga rivularis is restricted to the eastern CAA, while Saxifraga hyperborea is widespread across the CAA; the two species are easily distinguished by the presence of stolons only in Saxifraga rivularis . Our collection fills in a distribution gap in the widely disjunct amphi-Atlantic-amphi-Beringian distribution of Saxifraga rivularis .

Two subspecies have recently been recognized in Saxifraga rivularis : subsp. rivularis with an amphi-Atlantic distribution (and widespread in the eastern CAA) and subsp. arctolitoralis with an amphi-Beringian distribution ( Jørgensen et al. 2006, Brouillet and Elvander 2009, Elven et al. 2011). Jørgensen et al. (2006), Aiken et al. (2007) and Brouillet and Elvander (2009) considered subsp. arctolitoralis as present in Alaska, but not known from Canada. More recently, Westergaard et al. (2010) presented molecular evidence for the presence of subsp. arctolitoralis on southeastern Baffin Island and Greenland, suggesting long distance dispersal from Beringia in the post-glacial period. Elven et al. (2011) consider subsp. arctolitoralis as present also in the Yukon and the Mackenzie Delta area of the Northwest Territories and mention that there are also plants from Hudson Bay and northern Quebec and Labrador conforming in both DNA and morphology to the subspecies. The two subspecies may be distinguished by the following key (adapted from Jørgensen et al. 2006 and Brouillet and Elvander 2009):

1	Hypanthium densely covered with long stipitate glandular hairs, 0.3-0.6 mm long; flowering stem glabrous or sparsely hairy	Saxifraga rivularis subsp. arctolitoralis
-	Hypanthium sparsely covered with short stipitate glandular hairs, 0.1-0.3 mm long; flowering stem sparsely to densely hairy	Saxifraga rivularis subsp. rivularis

Specimens examined.

Canada. Nunavut: Kitikmeot Region, Victoria Island, Murray Point, W side of Wilbank Bay, 68°35'34"N, 110°18'24"W, 20-30 m, 21 July 2008, Gillespie, Saarela, Consaul & Bull 8174 (ALA, ALTA, BABY, CAN-592397, MT, O, UBC).