Flora of the Canadian Arctic Archipelago

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S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, L.J. Gillespie, A.K. Brysting, H. Solstad, and J.G. Harris

Oxytropis arctobia Bunge

Fabaceae (Leguminosae), Pea family.

Published in Bull. Soc. Bot. Genève, sér. 2, 2: 19. 1910.

Type: Nunavut: Barrow River, east coast Melville Peninsula, lat. 67°21'N, on Parry's Second Voyage. Isotypes: GH, NY.

Synonymy. Oxytropis nigrescens (Pall.) Fisch. subsp. arctobia (Bunge) Hultén, Ark. Bot., n. s., 7, 1: 80. 1968.

Oxytropis arctica R. Br. var. uniflora Hooker, App. Parry J. Sec. Voy. 396. 1825.

Oxytropis nigrescens (Pall.) Fisch. var. uniflora (Hooker) Polunin, Bull. Natl. Mus. Canada 94 (Biol. Ser. 24):

293. 1940.

Oxytropis nigrescens (Pall.) Fisch. var. uniflora (Hook.) Barneby, Proc. Calif. Acad. Sci., ser. 4, 27: 209.

1952.

Vegetative morphology. Plants 1–5 cm high; perennial herbs; caespitose (densely). Taproot present. Ground level or underground stems absent. Horizontal stems at ground level, branching extensively to shape plant habit as cushions. Caudex present (much branched under the cushions). Aerial stems erect. Leaves distributed along the stems (that are very compact); alternate; dying annually and non-persistent, or marcescent. Stipules present; persisting for 2 or more years; 2–5 mm long; 1.5–2.5 mm wide; not sheathing; white (or straw-coloured, appearing pale grey from the numerous hairs); hairy (stipule margins densely hairy, sometime with clavate processes); villous; apex obtuse. Petioles 5–15 mm long (not very obvious, 3–6 mm wide); hairy; villous. Leaf blades compound. Leaves not grass-like. Blades 50–80 mm long, 3–6 mm wide, with inconspicuous veins. Blade adaxial surface hairy, hairs villous, hairs simple, hairs dense, hairs white, or translucent. Blade abaxial surface hairy, hairs villous or short-silky, hairs very dense, hairs white, hairs straight or wavy, hairs appressed or spreading. Blade margins flat or slightly revolute. Blade apices acute. Leaflet arrangement pinnate. Leaflets (3–)5–9(–13); 3–4.5 mm long (often with the margins rolled inwards, and with dense grey hairs); 1–1.5 mm wide; oblong, or ovate; veins inconspicuous.

Reproductive morphology. Flowering stems without leaves. Flowering stems hairy. Flowering stems strigose. Flowering stem hairs simple (pointing towards the flower); longer than the diameter of the flowering stem; white or translucent. Flowers solitary, or in inflorescences (of two flowers; often numerous flowers on a cushion). Inflorescences spicate (if applicable); diffuse; not elongating as the fruit matures. Floral scales hairy all over (pilose stipules). Flowers per inflorescence 1(–2); medium-sized, or large; bilaterally symmetrical (zygomorphic). Sepals conventional; 5; fused; 8–9 mm wide; green, or brown, or black (because of black hairs). Calyx tubular; 5-lobed; hairy. Calyx hairs pilose, or villous; non-glandular; white or translucent, or black. Calyx teeth 2–3 mm long. Petals conventional; both free and fused; 5; purple, or blue (pinkish purple); with contrasting markings (the banner petals purplish in the upper half, white below, yellow insect guidelines along veins and towards the base of the petals); unlobed (4 petals), or slightly lobed or undulating (banner petal); 8–12 mm long. Corolla papilionaceous; keel with a pointed tip; helmet without 2 small teeth at the apex. Stamens 10. Anther filaments 9 fused into a tube, plus 1 free. Nectaries present. Ovary superior; carpels 1; monomerous. Stigmas per ovary 1. Ovules per ovary 16–20. Fruit sessile (within hte calyx); with calyx persisting; dry; a legume; ellipsoid, or elongate-cylindrical; black; (15–)25–30 mm long; 6–9 mm wide; hairy; not distinctly flattened; dehiscent; splitting to the base into separate segments. Legume unilocular; valves straight. Seeds 10–20; 1.2–1.6 mm long (in the longest dimension); brown; surfaces smooth.

Chromosome information. 2n (2x) = 16.

Ploidy levels recorded 2x.

Taxon as an environmental indicator. Polunin (1940) reported the northernmost record as Baffin Island, Arctic Bay, 73°05'N. Since that time, it has been collected further north, on Eglinton Island, Kuc, 8 July 1968, 75°48'N.

Ecology and habitat. Substrates: hummocks (uncommonly), river terraces, ridges (very often); moderately well-drained areas; gravel (limestone), silt, clay; calcareous (locally). At anthesis this species is strikingly handsome when the firm grey cushions of large individuals may be covered with several hundred flowers. In fruit the legumes are large and black and show up against the ashygrey foliage, which otherwise tends to blend in with the grey gravel on which it grows (Polunin 1940).

North American distribution. Range in the Canadian Arctic Archipelago limited. Common. Arctic (endemic to the central Canadian Arctic from Banks Island to Baffin Island, also on Melville and Boothia peninsulas and the south coast of Baffin, Southampton, and adjacent islands in Hudson Bay). Arctic islands: Baffin, Parry islands (Eglinton), Banks, Victoria, King William, Southampton (and Boothia Peninsula).

Northern hemisphere distribution. North American. Central Canada.

General notes. Elven et al. (2003) reported a major discussion on the Oxytropis nigrescens aggregate (O. nigrescens, O. pumilio, ?O.sublongipes). They noted that this aggregate was proposed as 8–9 separate species in Yurtsev's draft for Elven et al. (2003). The North American view is to consider the entire American part of the aggregate as one variable species with 'varieties' (Barneby 1952, later taken up by Gillett et al. 1999 onwards). As the varieties mostly occupy different regions, they would more naturally be subspecies in the Panarctic Checklist concept (Elven et al. 2003). This is also supported by the ranges of the major entities: nigrescens s.s. from Jenisei to Kolyma, 'czukotica' from Kolyma to the Bering Strait, 'pygmaea’ ('gorodkovii’) around the Bering Strait, 'bryophila’ in Alaska-Yukon, and 'arctobia’ in northern Canada. They are all diploid or tetraploid, parapatric, and closely related. Because the nomenclatural conclusions are still not completely resolved, we are using the specific rank for the Canadian entity 'arctobia', following Yurtsev's draft for Elven et al. (2003).

Polunin (1940) noted that there is a specimen of this species in the Gray Herbarium among a collection that has often been referred to as coming from Melville Island, but actually was made far to the southeast during Parry’s second voyage. He indicated that the Arctic Bay material differs from all other specimens that he had examined in having seeds that are light brown instead of almost black when ripe, and having the insides of the pods essentially glabrous instead of flocculent-pubescent. The pubescence on the outside also tends to be less dense and spreading. On these characters he recognised O. arctobia var. hyperarctica Polunin. This name and the recognition of this taxon has not been widely taken up.

Illustrations. • Habitat: Banks. Plants growing on south-facing rocky sandy barren. N.W.T., Banks Island, Aulavik National Park, Shoran Lake, 7330'73N; 12021'W. 1 July, 1999. Aiken. No voucher. • Habitat: Baffin Island, Dorset. Plant near the marker and in adjacent tundra, growing on dry gravel with little competition. Common in similar sites around Dorset. Nunavut, Baffin Island, Cape Dorset. 4 August, 2005. Aiken. • Plant with flowers in bud: Banks Island. Flowers in bud. Note the very black sepals and the first sign of petal colour. The sepals are black because of black hairs on the sepals that appear to aid in warming the developing flower. N.W.T., Banks Island, Aulavik National Park, near Green Cabin. 29 June, 1999. Aiken SA99–015. CAN. • Flowers in bud. Note the black hairs on the sepals that appear to aid in warming the developing flower. N.W.T., Banks Island, Aulavik National Park, near Green Cabin. June 29, 1999. Aiken 99–015. CAN. • Plants with buds. Plant with closed and opening buds growing on south-facing rocky sandy barren. Note the very black sepals. Banks Island, Aulavik National Park, Shoran Lake. 1 July, 1999. Aiken 99–011. CAN. • Plant coming into flower. Note the two-coloured standard or banner petal, and sepals covered with black hairs. These possibly aid in warming the developing flower. N.W.T., Banks Island, Aulavik National Park, near Green Cabin. June 29, 1999. Aiken 99–015. CAN. Scale bar in cm. • Plant coming into flower. Note the two-coloured standard or banner petal, and the rounded or lobed calyx teeth. The sepals are covered with black and white hairs which possibly aid in warming the developing flower. 29 June, 1999. Aiken 99–015. CAN. • Close-up of flower. Flower with contrasting markings on the standard or banner petal. N.W.T., Banks Island, Aulavik National Park, near Green Cabin. 29 June, 1999. Aiken 99–015. CAN. • Habitat. Plant covered with a mass of flowers, growing with Dryas on south-facing rocky sandy barren. Banks Island, Aulavik National Park, confluence of Thomsen and Muskox Rivers. 13 July, 1999. Aiken 99–062. CAN. Scale bar in cm. • Plant habit. Flowers, initially purple and erect, fading to blue and becoming more or less prostrate. Banks Island, Aulavik National Park, Muskox River. 9 July, 1999. Aiken 99–062. CAN. • Habitat: Dorset. Isolated plants growing in cryptogamic mat with Dryas cushions in the area. Plants on hilltop near Federal building. Nunavut, Baffin Island, Cape Dorset,. 3 August, 2005. Aiken. No voucher. • Close-up of developing pods. Note hairs on the surface of the pods are both black and white. Nunavut, Baffin Island, Cape Dorset. 3 August, 2005. Aiken. No voucher. • Plant with seed pods. Previous season's seed pods lying on the tundra. Flowers in bud. N.W.T., Banks Island, Aulavik National Park, near Green Cabin. June 29, 1999. Aiken 99–015. CAN. Scale bar in cm. • Close-up of seed pods. Previous season's seed pods lying on the tundra. N.W.T., Banks Island, Aulavik National Park, near Green Cabin. June 29, 1999. Aiken 99–015. CAN. • Arctic island Distribution.


This publication is available on the internet (posted May 2011) and on CD-ROM (published in 2007). These versions are identical in content, except that the errata page for CD-ROM is accessible on the main index page of the web version.

Recommended citation for the web-based version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. NRC Research Press, National Research Council of Canada, Ottawa. http://nature.ca/aaflora/data, accessed on DATE.

Recommended citation for the CD-ROM version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. [CD-ROM] NRC Research Press, National Research Council of Canada, Ottawa.

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