The Flora of Svalbard

Perennial, but probably not long-lived.

Solitary herb with basal caudex, sparsely covered by leaf remains, singly or branching into a few (rarely numerous), densely to loosely clustered rosettes forming tussocks. Each rosette potentially with one flowering stem without leaves, up to 10 or more per tussock.

Leaf rosettes usually 3–6 cm broad, sometimes broader. Leaves dark green, narrowly to broadly oblanceolate, acute, up to 10(–13) × 3–5 mm, entire or very rarely with a few teeth, midvein prominent (especially on withered leaves). Upper leaf surface glabrous; lower leaf surface distally with minute, multibranched hairs (sometimes very few or absent), sometimes a few long, simple hairs along midvein; margin with long, stout, simple hairs or more rarely a few forked hairs up to 1 mm (sometimes absent). Simple hairs not strongly directed forward (difference from D. fladnizensis).

Flowering stems ascending to erect, scarcely elongating during or after flowering, up to 10 cm, never observed with a leaf (except for occasional bracts), glabrous or rarely with sparse, small, multibranched, forked, and/or simple hairs. Inflorescence a short raceme, more or less corymbose even in the fruit stage, up to 2.5 cm, with (3–)5–8 flowers. Pedicels slender, attached at an angle of 40–60° with stem but regularly curved upwards, mostly 3–5 mm, more than half the fruit length, glabrous.

Flowers radially symmetric with four sepals and petals. Sepals green or red tinged, ovate or more rarely elliptic, up to 2 × 1.5 mm (i.e., less than twice as long as broad), mostly with white margins. Petals milky white, patent (making the flower more open than in most other white-flowered Drabas at the flowering peak), obovate, slightly notched, 3.5–4 × 1.75–2(– 2.5) mm, twice as long as sepals, often contiguous.

Fruit a silicule, dark green, partly spreading or spreading, lanceolate or rarely ovate, mostly acute, 4–8 × 1.75–2(–2.5) mm, glabrous. Style mostly > 0.3 mm. Seeds 9–10 in each room, dark brown, ca. 1.2 × 0,8 mm.

Reproducing only by seeds. Flowering and seed-set is regular in most years; mature seeds are often observed. Germinability of seeds around 70% (Alsos et al. in prep). A mixed mater with a certain level of outcrossing (Brochmann 1993). Seedling establishment is commonly observed, especially in disturbed sites, but must also be a regular feature in more stable sites.

Draba fladnizensis, D. subcapitata, D. nivalis, and partly D. lactea and D. “norvegica” are the small-grown, white-flowered species of Draba in Svalbard and are often confused. Draba nivalis is, however, easily recognizable by being (usually) densely grey-pubescent on leaves and scapes up to the pedicels with minute, regularly stellate hairs less than 0.2 mm broad with ca. 8 patent to erectopatent branches (strong lense or microscope). The others have either no regularly stellate hairs (D. fladnizensis, D. subcapitata, D. lactea) or may have coarse stellate hairs with much fewer branches (parts of D. “novegica”). Irregularly multibranched hairs are typical of the stems of D. subcapitata, the leaves and stems of D. “norvegica” (but see below), and the apical parts of the lower leaf surface of D. lactea. Glabrous stems are typical of D. fladnizensis and D. lactea, but the latter species may have stems sparsely pubescent with multibranched hairs. Small petals up to 2.5 mm distinguish D. fladnizensis, D. nivalis, and D. subcapitata from the others, in the last-mentioned species also very narrow petals. The two others have longer petals, 3.5–5 mm. Draba norvegica may have pubescent fruits, whereas all the others predominantly have glabrous fruits (pubescent fruits have been observed in a few D. nivalis and D. subcapitata). Draba lactea is usually characterized by leaves with coarse marginal hairs combined with minute multibranched hairs on the lower surface; this combination is unique for that species. The most problematic species to characterize is D. “norvegica”, probably due to the inclusion of two or more separate species in what currently is considered within a single species.. It may be completely glabrous, as may be D. lactea, but then mostly characterized by the shape of infrutescence (elongated in the former vs. corymbose in the latter), the shape of fruits (oblong to lanceolate–elliptic vs. lanceolate with acute apex), and the midvein on the leaves (conspicuously thickened vs. not conspicuous).

Not thermophilous. Occurs most frequently at rather moist growth sites such as next to water bodies (seepages, brooks, rivers, or lake shores), on moist patterned ground, in snowbeds, on moist, tussocks in mires, but also quite common in less wet heaths among dwarf shrubs and graminoids. A common species on moist road verges, both in Longyearbyen, Barentsburg, and Ny-Ålesund. Usually on fine textured sediments with poor to intermediate draining and circumneutral to basic reaction, but also sometimes reported from weakly acidic substrates. Growth sites range from moderately protected to slightly exposed. Probably little grazed by reindeer and geese.

Common to frequent in all zones and sections. One of the most hardy of all Svalbard plants. The documented range is, however, restricted to Spitsbergen, Nordaustlandet, and Barentsøya.

Draba lactea is a circumarctic, polymorphic, polyploid species shown by Brochmann et al.(1992) with fixed heterozygosity, indicating more than one, probably several, origins fromhybridizations among diploid species (based on Svalbard and Scandinavian plants). Thespecies has been assumed to be uniformly hexaploid (2n = 48), but cytological and geneticstudies have shown that also tetraploids (2n = 32) must be included in this species (Zhukova& Petrovsky 1984; Grundt et al. 2005). Some small morphological differences have beensuggested by Russian authors between the tetraploids and hexaploids, and they have partlyassigned the former under the name D. pseudopilosa Pohle, based on Siberian plants. Grundtet al. (2005) did not find support for a separation.Several authors concerned with the American plants have claimed transitions betweenD. fladnizensis and D. lactea to be common (e.g., Hultén 1945, 1968; Scoggan 1978). Suchclaims are unfounded; natural hybrids are unknown and artificial hybrids sterile. The claimsare based on an erroneous morphological concept of the two species (i.e., much D. lacteamisidentified as D. fladnizensis). Other authors have assumed the diploid D. fladnizensis to beparental, together with the diploid D. nivalis, in the predominantly hexaploid D. lactea (e.g., Knaben 1966). Also this claim seems to be unfounded and based on a provincial viewpointthat the hybridization behind the hexaploid D. lactea must have taken place among speciespresent in the North Atlantic regions. Grundt et al. (2004) rather point towards an origin of D.lactea from the Beringian diploid and tetraploid (2n = 16, 32) D. palanderiana.

Alsos, I.G., Müller, E. & Eidesen, P.B. In prep. Germinability of 87 arctic species stored in Svalbard Global Seed Vault.

Brochmann, C., Soltis, D.E. & Soltis, P.A. 1992. Electrophoretic relationships and phylogeny of Nordic polyploids in Draba (Brassicaceae). – Plant Systematics and Evolution 182: 35–70.

Grundt, H.H., Kjølner, S., Borgen, L., Rieseberg, L.H. & Brochmann, C. 2006. High biological species diversity in the arctic flora. – Proceedings of the National Academy of Sciences 103: 972−975.

Grundt, H.H., Obermayer, R. & Borgen, L. 2005. Ploidal levels in the arctic–alpine polyploid Draba lactea (Brassicaceae) and its low-ploid relatives. – Botanical Journal of the Linnean Society 147: 333–347.

Grundt, H.H., Popp, M., Brochmann, C. & Oxelman, B. 2004. Polyploid origins in a circumpolar complex in Draba (Brassicaceae) inferred from cloned nuclear DNA sequences and fingerprints. – Molecular and Phylogenetic Evolution 32: 695–710.

Hultén, E. 1945. Flora of Alaska and Yukon. V. Dicotyledoneae. Rhoeadales, Sarraceniales, Rosales I (Crassulaceae, Saxifragaceae). – Acta Universitas Lundensis, n. s., sect. 2, 41, 1: 797–978.

Hultén, E. 1968. Comments on the flora of Alaska and Yukon. – Arkiv för Botanik, ser. 2, 7, 1. 147 pp.

Knaben, G. 1966. Cytotaxonomical studies in some Draba species. – Botaniska Notiser 119: 427–444.

Scoggan, H.J. 1978. The Flora of Canada. 3. Dicotyledoneae (Saururaceae to Violaceae) (pp. 547–1115). – National Museum of Natural Sciences, National Museums of Canada, Ottawa.

Zhukova, P.G. & Petrovsky, V.V. 1984. Tsitotaksonomicheskoe izuchenie nekotorykh vidov krestotsvetich (Brassicaceae) iz severnoi Azii. – Botanicheskii Zhurnal 69: 236–240.