Flora of the Canadian Arctic Archipelago
English: Arctic rockcress,
French: Arabette des sables.
Brassicaceae (Cruciferae), Draba family.
Published in Can. J. Bot. 84: 279. 2006.
Type: Deep sand upon shores of Arctic America between longitude 107°W and 150°W. Dr. Richardson (Isotype: CAN!)
Synonymy. Eutrema arenicola Richardson ex Hooker, Fl. Bor.-Amer. 1: 67. 1829.
Arabis arenicola var. pubescens (Wats.) Gelert., Bot. Tidsskr. 21: 290. 1898.
Arabis humifusa S. Watson var. pubescens S. Watson, in A. Gray, Syn. Fl. N. Amer. 1, pt. 1 160. 1895.
Vegetative morphology. Plants 2–15 cm high; perennial herbs; caespitose. Taproot present. Ground level or underground stems absent. Caudex present (much branched). Aerial stems erect, or decumbent. Leaves mainly basal and distributed along the stems; alternate; dying annually and non-persistent. Petioles present. Leaf blades simple. Leaf blade bases attenuate. Blades 7–10 mm long, 3.5–4.5 mm wide, oblanceolate or spatulate, flat, appearing single-veined. Blade adaxial surface dull, without sessile glands, glabrous (almost) or hairy, hairs isolated hairs, hairs branched, hairs sparse, hairs white, or translucent (often with salt glands). Blade abaxial surface dull, hairy. Blades not lobed. Blade margins entire or dentate (repand dentate), with non-glandular hairs, with teeth all around the blade. Hydathodes present but inconspicuous (at the tips of the leaf dentations). Blade apices obtuse.
Reproductive morphology. Flowering stems two or more per plant; conspicuously taller than the leaves; with leaves. Inflorescences racemose; elongating as the fruit matures. Pedicels present; with non-glandular hairs. Flowers per inflorescence 6–15; small; radially symmetrical (actinomorphic). Sepals conventional; 4; free; 1.4–2 mm long; (2–)2.5–3.2 mm wide; green, or yellow (cream), or purple; herbaceous. Calyx hairy. Calyx hairs with sparse, scattered simple hairs; non-glandular; white or translucent. Petals conventional; free; longer than the calyx; 4; white, or pink and purple; without contrasting markings; obovate; unlobed; 3.5–4.5(–5.5) mm long; 1.3–3 mm wide. Stamens 6; stamen filaments markedly unequal in length; stamen filaments glabrous. Anthers yellow; (0.2–)0.4–0.5 mm long. Ovary superior; carpels 2; syncarpous. Ovaries oblong; glabrous. Styles 1; thick and short; 0.2–0.3 mm long. Stigmas per ovary 1. Placentation parietal. Ovules per ovary 40–55. Fruit stalked; stalk 5–6 mm long; dry; a silique (short but with a definite gynophore 0.5–1 mm long, rare in the genus); elongate-cylindrical; purple; (12–)15–20(–25) mm long; 1.5 mm wide; glabrous; dehiscent; shedding the outer walls to expose a thin inner wall, with the seeds attached at the margins on either side. Styles remaining straight; persisting in fruit 0.5–0.8 mm long. Seeds 16–32(–40); 1–1.3 mm long; brown; surfaces smooth (mucilaginous when placed in water).
Chromosome information. 2n = 16.
2n = 16. Böcher (1966, Greenland); Hedberg (1967, northern Canada); Löve and Löve (1982, Arctic Canada).
Ploidy levels recorded 2x.
Ecology and habitat. Substrates: imperfectly drained moist areas, dry, moderately well-drained areas; gravel, sand; with low organic content. Elven (personal communication, 2005) described the arenicola s.s. entity as occurring on all kinds of open sand and gravel, from comparatively dry to wet, and often in ruderal or temporal situations (land slides, fine scree, river and creek banks, lake shores). He noted that where he had seen it in northeastern Canada, the substrate has been acidic, but I have only seen it a very few times. Translation from the Greenland flora: "In sandy or gravelly places, river courses".
North American distribution. Nunavut Islands, continental Nunavut, northern Quebec, Labrador, Newfoundland (introduced to northern Newfoundland, personal communication, Peter Scott, Dec. 2004). Range in the Canadian Arctic Archipelago limited. Uncommon. Low Arctic. Arctic islands: Baffin, Southampton.
Northern hemisphere distribution. North American (American Atlantic. Elven (personal communication, 2005) noted that this taxon is circumpolar in the Al-Shehbaz et al., 1999, concept of the taxon). Central Canada, Labrador Hudson Bay, Ellesmere Land Peary Land, West Greenland, East Greenland (Ic UN YG Tm AO Kh YK? CW WI? CS? AW AN CC LH EP GW GE, in the Al-Shehbaz et al. 1999 concept of the taxon).
General notes. Elven et al. (2003) noted that according to O'Kane and Al-Shehbaz (1997), Novon 7: 323–327, and Al-Shehbaz et al. (1999), Novon 9: 296–307, this genus should be confined in a northern context to A. thaliana, A. arenosa, A. suecica (the alloploid from A. arenosa and A. thaliana, named as Hylandra by Á. Löve), and the A. kamtschatica-lyrata-petraea group. This approach was followed by Elven et al. (2003). It is also strongly supported by the recent works of Koch et al. (1999, 2000, 2001). Their analyses connect A. thaliana, A. suecica, and the A. kamtschatica-lyrata-petraea group inside an Arabidopsis s.s.
Illustrations. • Habitat: Dorset. Plants growing with Leymus on the beach. Note reddish leaves on small plant in more exposed habitat. 5 August, 2005. Aiken. No voucher. • Close-up of flowering and fruiting plant. Plant with inflorescences in flower and in fruit, lying on the tundra. Nunavut, Baffin Island, Cape Dorset. 2 August, 2005. Aiken. No voucher. • Close-up of flower. Flower with four petals, four anthers opposite the petals and two anthers that alternate with the petals. White petals turn pinkish as the flower fades. Nunavut, Southampton Island. 30 July, 2001. Aiken and Brysting 01–081. CAN. • Close-up of flower. Flower with four pale white petals that are turning pinkish, six anthers, a bi-lobed yellow stigma covered with pollen from other flowers, and a reddish brown wall on the gynoecium that will develop into the fruit. Nunavut, Southampton Island. 30 July, 2001. Aiken and Brysting 01–080. CAN. • Close-up of leaves. Plant growing in dry sandy gravel. The presence of petioles helps distinguish this species from Arabis alpina. The presence of hairs on the leaves distinguishes these plants as var. pubescens (Wats.) Gel. Manitoba, Churchill, Northern Studies Centre. 22 July, 2001. Aiken and Brysting 01–010a. CAN. • Plant habit. Plants in the late stages of flowering and with developing fruit. Nunavut, Baffin Island, Iqaluit. 25 July, 1982. J.M. Gillett 19053. CAN. • Close-up of fruit. White petals turn pinkish and fall before the calyx turns from green to pinkish and falls off. Note the white gynophore (a stalk bearing the gynoecium) between the receptacle and the developing silique. Nunavut, Southampton Island. 30 July, 2001. Aiken and Brysting 01–080. 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..