The Flora of Svalbard

Reproducing only by seeds. Flowering and seed-set is regular in most years; mature seeds are often observed. Draba fladnizensis is known to be highly selfing (Brochmann 1993). Grundt et al. (2006) found sterility barriers between populations of D. fladnizensis to be quite frequent in the circumpolar area. Crosses between several populations from Svalbard and populations from S Norway and Alaska were included.

Draba fladnizensis is characterized by having only simple and sometimes forked, forward pointing hairs on the leaves, and glabrous stems and fruits. The only other white-flowered Draba in Svalbard with a predominance of simple hairs on the leaves (and glabrous stems and fruits), is D. lactea. This species, however, nearly always have some very small, multibranched hairs on the outer parts of the lower surface of leaves, and also much broader leaves with less strengthened mid-vein, larger petals (3.5—4 mm long vs. 2—2.5 mm), a more corymbose panicle, and fruits lanceolate or ovate vs. mostly elliptic.

Draba fladnizensis is clearly a thermophilous species with an affinity for sites with higher insolation rates. Occurs in sparsely vegetated environments such as crevices and rock ledges, gravelly slopes and ridges. On dry to very dry substrates of well drained soils of mixed or coarse texture and with circumneutral to basic reaction. The growth sites are usually exposed or semi-exposed, with little snow cover in winter and little competition. Little grazed by reindeer and geese.

Draba fladnizensis is an arctic−alpine, diploid (2n = 16) species distributed throughout the Arctic and in the majority of temperate mountain ranges in Europe, Asia, and North America. It is recognizable everywhere and monomorphic, so that no feature has been found to distinguish, e.g., European, Asian, or American plants. Grundt et al. (2006) have, however, shown that this morphologically and cytologically uniform species include several cryptic species separated by sterility barriers, present both within and between regions (e.g., N Europe and Alaska).

Several authors concerned with the American plants have claimed transitions between D. fladnizensis and D. lactea to be common (e.g., Hultén 1945, 1968; Scoggan 1978). Such claims are unfounded; natural hybrids are unknown and artificial hybrids sterile. The claims are based on an erroneous morphological concept of the two species (i.e., much D. lactea misidentified as D. fladnizensis). Other authors have assumed the diploid D. fladnizensis to be parental, 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 provisional viewpoint that the hybridization behind the hexaploid D. lactea must have taken place among species present in the North Atlantic regions. Grundt et al. (2004) rather point towards an origin from the Beringian diploid and tetraploid (2n = 16, 32) D. palanderiana.

Even if D. fladnizensis is monomorphic, a few plants from Svalbard have been difficult to place within this global uniform pattern. They are from two populations from inner Wijdefjorden on Spitsbergen, found in 2010. They have a leaf pubescence different from any D. fladnizensis inspected worldwide, and are under investigation.

Brochmann, C. 1993. Reproductive strategies of diploid and polyploid populations of Arctic Draba (Brassicaceae). – Plant Systematics and Evolution 185: 55−83.

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., 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.