Flora of the Canadian Arctic Archipelago
English: Snow draba, Snow whitlowgrass,
French: Drave des neiges.
Brassicaceae (Cruciferae), Draba family.
Published in Utkast Sv. Fl. 236. 1792
Type: Described from Scandinavia; not typified.
Synonymy. Draba caesia Adams, in Mém. Soc. Nat. Mosc. 5. 108. 1817.
Vegetative morphology. Plants (1.5–)3–10(–15) cm high; perennial herbs; caespitose. Taproot present. Ground level or underground stems vertical; compact (forming a loose cushion). Horizontal stems at ground level, branching extensively to shape plant habit as mats (of rosettes). Caudex present (much branched). Aerial stems erect. Aerial stem trichomes spreading, or erect. Leaves mainly basal; alternate; dying annually and non-persistent. Petioles absent. Leaf blades simple. Leaf blade bases attenuate and truncate. Leaves not grass-like. Blades 3–12(–14) mm long, 0.8–2 mm wide, linear or oblong (strap-like), appearing single-veined or with inconspicuous veins. Blade adaxial surface hairy, hairs branched (irregularly) or stellate (with short basal stalks so that the hairs lie close to the surface), hairs sparse or moderately dense (appearing dense from the branching), hairs white, or translucent. Blade abaxial surface hairy, hairs sparse or moderately dense (appearing dense from the branching), hairs white, hairs irregularly branched or stellate, hairs appressed or spreading. Blade margins entire, with non-glandular hairs (similar to the leaf surface); apices acute.
Reproductive morphology. Flowering stems two or more per plant; without leaves (or occasionally a single leaf). Flowering stem hairs branched (irregularly), or stellate; white or translucent. Inflorescences head-like (in flower), or racemose (in fruit); dense (in flower), or diffuse (in fruit); globose or sub-globose (in flower); elongating as the fruit matures. Pedicels with non-glandular hairs. Flowers per inflorescence 2–12; small (relatively small for a Draba); radially symmetrical (actinomorphic). Sepals conventional; 4; free; 0.6–1.1 mm long; 1.6–2.2 mm wide; green (greyish from hairs), or purple (slightly); herbaceous. Calyx hairy (with irregularly branched hairs). Calyx hairs non-glandular; white or translucent. Calyx margins without cilia. Petals conventional; free; 4; white; without contrasting markings; obovate, or spatulate, or obtriangular; slightly lobed or undulating; (2–)2.3–2.7 mm long; 1.2–1.7 mm wide (at apex, 0.3–0.4 mm wide at base). Stamens 6; stamen filaments markedly unequal in length; stamen filaments glabrous. Anthers yellow; ovoid; 0.2–0.4 mm long. Ovary superior; carpels 2; syncarpous. Ovaries ovate, or oblong; glabrous. Styles 1; 2.5–3.5 mm long; straight (stout). Stigmas per ovary 1. Placentation parietal. Ovules per ovary 10–20. Fruit stalked; stalk 4–8 mm long; dry; a silique; ellipsoid, or elongate-cylindrical; purple, or green at maturity; (3–)4–7(–8.5) mm long; (1.2–)1.5–2.5 mm wide (fruit conspicuously variable in size); glabrous (and somewhat shiny); surface appearing veinless (or with a single vein); distinctly flattened; dehiscent; shedding the outer walls to expose a thin inner wall, with the seeds attached at the margins on either side. Styles persisting in fruit 0.2–0.4(–0.6) mm long. Seeds (12–)16–20(–24); 0.8–1 mm long; brown; surfaces verrucose.
Chromosome information. 2n = 16.
2n = 16. Heilborn (1927, Norway, Sweden); Löve and Löve (1956, Iceland); Jørgensen et al. (1958, Greenland); Zhukova (1965b, Wrangel Island); Knaben (1966, Norway); Knaben and Engelskjøn (1967, Norway); Johnson and Packer (1968, Alaska); Mulligan and Porsild (1969b, Yukon); Zhukova and Petrovsky (1971, 1984, northeastern Asia); Zhukova and Tikhonova (1971, 1973, Chukotka); Zhukova et al. (1973, northern and northeastern Asia; Mulligan (1974b, northern and western Canada, 12 counts); Berkutenko and Gurzenkov (1976, northeastern Asia); Dawe and Murray, in Löve (1980b, Alaska; 1981a, central Alaska, as D. lactea, voucher checked and found to be subglabrous D. nivalis); Zhukova and Petrovsky (1980, western Chukotka; 1984, northern and northeastern Asia); Berkutenko et al. (1984, northeastern Asia); Brochmann et al. (1993, Svalbard); Grundt (unpublished, Alaska, Canada, Greenland, Svalbard, Norway, Siberia, diploid in cytometry); Mulligan (2003).
Ploidy levels recorded 2x.
Ecology and habitat. Substrates: river terraces, slopes, ridges, cliffs; seepage slopes, dry; rocks, gravel; with low organic content; acidic (unlike many other drabas, this species has a preference for acidic outcrops in the Arctic). Wet ground on cliffs (CAN 273756); rock ledges (CAN 393486); gravelly beaches just above high tide (CAN 296015); owl nest on sand (CAN 301989); dry sandy bank (CAN 204720).
North American distribution. Alaska, Yukon, Northwest Territories Islands, continental Northwest Territories, Nunavut Islands, continental Nunavut, northern Quebec, Labrador. Range in the Canadian Arctic Archipelago widespread. Common. Arctic, alpine. Arctic islands: Baffin (Bylot), Devon, Ellesmere, Somerset, Southampton (Melville Peninsula).
Northern hemisphere distribution. Circumpolar and circumboreal (arctic-alpine). Northern Iceland, Northern Fennoscandian, KaninPechora, Svalbard Franz Joseph Land, Polar Ural Novaya Zemlya, YamalGydan, Kharaulakh, YanaKolyma, West Chukotka, South Chukotka, East Chukotka, West Alaska, North Alaska Yukon, Central Canada, Labrador Hudson Bay, Ellesmere Land Peary Land, West Greenland, East Greenland.
General notes. The Draba nivalis aggregate consists of D. kamtschatica, D. lonchocarpa, D. nivalis, D. palanderiana, and possibly D. magadanensis (Elven et al. 2003). The five species listed constitute a group of comparatively closely related low-ploids. The aggregate also contains several non-arctic species, e.g., the Cordilleran and tetraploid (2n = 32) D. porsildii G.A. Mulligan that reaches north to non-arctic Yukon Territory and east-central Alaska. Only D. nivalis is found in the Flora region.
Draba nivalis is exclusively known as diploid with 2n = 16. The species is thought to be inbreeding (Brochmann 1993). The morphology of this species is not as straightforward as previously thought. Draba nivalis with stellate hairs only on the leaf margins exists, and these individuals have frequently been confused with D. lactea (e.g., see above). Populations being completely glabrous have also been found both from Alaska and Greenland. That they belong to the nivalis taxon has been confirmed by RAPD analysis (Grundt et al. 2004), but they have most certainly been confused with D. fladnizensis. Crossing experiments within populations of D. nivalis (Grundt et al. 2005a) has shown that several of these populations are inter-sterile.
Draba caesia Adams represents a synonym or a variety of D. nivalis, and has wrongly been confused with D. palanderaina Kjellm. especially by North American authors, according to Petrovsky (1971). Elven (personal communication, 2005) noted that he and Hanne Grundt had looked at all syntypes (original Adams collections) in G-DC and in both herbaria in Moscow. Each and every syntype belonged to D. nivalis. Adams was probably unaware of D. nivalis Lilj. when he described D. caesia, as he never referred to it.
Illustrations. • Habitat. Plants with small white flowers growing between the markers and on the adjacent rocky tundra. Nunavut, Baffin Island, Ogac Lake. 15 July, 2004. Aiken and LeBlanc 04–096. CAN 586568. • Close-up of plants. Plants with basal rosette of leaves and small white flowers growing between the markers. Nunavut, Baffin Island, Ogac Lake. 15 July, 2004. Aiken and LeBlanc 04–096. CAN 586568. • Side view of plant. Plants with basal leaves, flowering stems without leaves, and small white flowers, some of which are beginning to form siliques. Aiken and LeBlanc 04–096. CAN 586568. • Close-up of developing silique. Developing siliques isolated from the inflorescence to show hairs on the surface. Aiken and LeBlanc 04–096. CAN 586568. • Habitat. Plants growing among rocks in disturbed roadside gravel. Nunavut, Baffin Island, Iqaluit. Aiken and Mallory 02–010. CAN. Scale bar in cm. • Close-up of inflorescences. Compact inflorescences of relatively few white flowers. Nunavut, Baffin Island, Iqaluit. Aiken and Mallory 02–009. CAN. • Close-up of tussock. Non-flowering tussock of rosettes. Leaves grey because of a very dense cover of minute stellate hairs. Alaska, Alaska Range, Susitna Mountains, Waterfall Creek. July, 1998. Voucher at 0. Photograph by R. Elven. • Close-up of leaves. Note basal rosette of small leaves that are greyish green from a cover of irregularly branched or stellate hairs. Note the leafless flowering stems are also covered with hairs. Aiken and Mallory 02–009. CAN. • Close-up of fruiting plant. Plant with inflorescences that have elongated in fruiting. Alaska, Alaska Range, Susitna Mountains, Waterfall Creek. July, 1998. Photograph by R. Elven. Voucher at 0. • Fruit shedding seeds. Fruiting plant less than 5 cm tall. Siliques have shed their outer walls and left elliptic to almost linear septa, each topped with a short stubby stigma. This specimen has a leafless stem, but occasionally the species may have one stem leaf. Alaska, Alaska Range. 1998. Hanne H. Grundt and Reidar Elven. coll. 5. O. Photograph by Hanne H. Grundt. • Fruiting plant. Plant growing in a dry cryptogamic mat. Note the half-moon shape of some siliques. The siliques are characteristically spreading from the flowering stem, at an angle of approximately 60–90°. Note grayish pubescent rosette leaves and stem. Alaska, Alaska Range. 1998. Hanne H. Grundt. coll. 8. O. Photograph by Hanne H. Grundt. • Close-up of plant. Drawing by Mrs. S. Bergh and Mrs. L. Barstad based on a collection from Svalbard, Nathorst Land, Fyrkanten i Sørfjorden. 13 July, 1920. J. Lid. 70. O 201388. With permission of the Botanical Museum, University of Oslo, Norway. • 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..