Place: Generalfjella, Krossfjorden
Place: Generalfjella, Krossfjorden
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).
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.
Scientific name, meaning and origin:
Draba: From greek drabe, sharp or besk, birning. Name on honningkarse hos Dioskorides, 70.
lactea, lacteus: Milkywhite.See all
|English name:||Lapland hitlow-grass|
|Distribution on Svalbard:|
|Chromosome number (2n):||32 48|
|Main mode of pollination:|
|Source: Brochmann, C. & Steen, S.W, 1999 - Sex and genes in the flora of Svalbard|