Stuckenia vaginata (Turcz.) Holub, 1984

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 : 40

Stuckenia vaginata (Turcz.) Holub Fig. 10

Potamogeton vaginatus Turcz.

Stuckenia subretusa (Hagstr.) Holub

Common name.

Big-sheathed pondweed

Distribution.

Circumboreal

Comments.

This collection is the first record of this primarily boreal species for the CAA. The species has a scattered distribution across Canada north to treeline and reaches the Arctic in coastal Yukon, coastal mainland Northwest Territories, and southeastern mainland Nunavut ( Porsild and Cody 1980, Haynes and Hellquist 2000b, Saarela et al. 2013a). The nearest site on the mainland is in the Northwest Territories near the coast just northwest of the border with Nunavut (Scotter & Zoltai 90-494, DAO; Saarela et al. 2013a), some 440 km west-northwest of our site. A slightly closer record (ca. 400 km) was mapped from eastern Great Bear Lake in Porsild and Cody (1980) (presumably based on a specimen collected by A.E. Porsild housed at GH, as cited by Raup 1947, no collection number given). A probable duplicate at CAN (Great Bear Lake, N shore of McTavish Arm, Black Rock, Laurentian, about 66°20'N, 118°30'W, 6 August 1928, Porsild & Porsild 6186, CAN-7215, det. Potamogeton vaginatus by M. Fernald) was re-determined as Coleogeton filiformis subsp. occidentalis (J.W. Robbins) Les & R.R. Haynes (= Stuckenia filiformis subsp. occidentalis (J.W. Robbins) R.R. Haynes, Les & M. Král) by C.B. Hellquist, and the site was not mapped for Stuckenia vaginata in Haynes and Hellquist (2000b).

Following the treatment by Kaplan (2008) Stuckenia vaginata may be distinguished by its open leaf sheaths from Stuckenia filiformis (Pers.) Börner, the only species of the family known to occur in the CAA prior to this collection. Although Stuckenia vaginata is generally more robust in habit with wider leaf sheaths and more numerous whorls of flowers on the inflorescence (usually 7-9 versus 3-6 in Stuckenia filiformis ), our collection from the northern edge of its range was somewhat intermediate in size with few young inflorescences (and no fruit) having 5-7 whorls of flowers.

The taxonomy of Stuckenia Borner is complex and there are several conflicting taxonomic treatments (e.g., Tolmachev et al. 1995, Haynes and Hellquist 2000b, Kaplan 2008; see discussion in Elven et al. 2011). Our collection was initially identified by R. Elven in 2009 as Stuckenia subretusa (Hagstr.) Holub, a primarily Russian Arctic species, based on its retuse or subretuse leaf apices. Although included in the Panarctic Flora, Elven et al. (2011) were not fully convinced that it should be treated as distinct and suggested a possible alternative treatment within a variable Stuckenia filiformis . Tolmachev et al. (1995) recognized Stuckenia subretusa in their treatment for the Russian Arctic, but suggested it might be an arctic race of Stuckenia vaginata . Kaplan (2008) in his revision of Asian Stuckenia treated Stuckenia subretusa as a synonym of Stuckenia vaginata (both have open leaf sheaths contrasting with the fused leaf sheaths of Stuckenia filiformis ); he found leaf apex shape to vary within specimens and (sub)retuse leaf apices on collections from across the range of Stuckenia vaginata . Saarela et al. (2013b) in their barcode study of Canadian Arctic Island vascular plant species found that the rbcL and matK sequences of our collection (as Stuckenia subretusa ) were identical to those of Stuckenia vaginata , and different from Stuckenia filiformis , consistent with Kaplan’s (2008) treatment. Here we follow Kaplan (2008) in treating Stuckenia subretusa as a synonym of Stuckenia vaginata , but also recognize that the species complex in North America is in need of further study. If Stuckenia subretusa is considered a distinct species, our collection would represent the first record for Canada (and is the one referred to in Elven et al. (2011) documenting presence of the species on Victoria Island and in Canada). If treated within Stuckenia filiformis , our collection would represent the first record for the western CAA.

Specimens examined.

Canada. Nunavut: Victoria Island, Kitikmeot Region, Johansen Bay, 18 km ENE of airstrip, Nakoyoktok River at outflow of large unnamed lake, 68°39'25"N, 110°42'30"W, 20-30 m, 18 July 2008, Gillespie, Saarela, Consaul & Bull 8048 (ALA, ALTA, BABY, CAN-592375, MT, O, UBC, US).