Life span

Perennial, moderately long-lived.

Growth form

Solitary or weakly mat-forming herb with short subterranean rhizome, extensively branched at or below ground level, densely to laxly caespitose with stems procumbent at base, erect above. Erect parts of stems 2–10 cm, glabrous in proximal part, with very short, stout, white hairs in distal part.

Leaf

Leaves alternate. Basal and stem leaves equal, numerous, semi-perennial (staying green over winter but withering during the second summer), retained as marcescent for several years after withering. Leaves 6–10 × 1.5–2.5 mm, without sheathing petiole, narrowly oblong, subacute, with a few short teeth or entire, thick and glabrous.

Inflorescence

Flowers terminal on stem, singly or more rarely 2–3 in a short cyme.

Flower

Flowers radially symmetric with 5 free sepals and petals. Sepals 2.5–3.5 × 1.5–2.2 mm, ovate or broadly ovate, obtuse, appressed or spreading in both flower and fruit stage, yellowish green. Petals 3.5–6.0 × 1.5–2.2 mm, narrowly oblong or ovate, obtuse, non-overlapping, bright yellow. Stamens 10. Ovary semi-inferior, of two carpels with two rooms, split apically.

Fruit

Fruit a capsule with numerous seeds.

Reproduction

Sexual reproduction by seeds; very restricted vegetative reproduction by fragmentation of mats. Flowers adapted to insect pollination; however, according to studies from other regions, selfing may be common (Brochmann et al. 1999). Flowering late in the season, in some sites intermittently, and no ripe seeds were found in 2008 (Alsos et al. 2013).

Capsules have apical opening which ensures that the seeds only are dispersed at a minimum wind speed. Seed dispersal is often after the first snow fall, which increases the dispersal distance as the seeds are blown across a smooth surface (Savile 1972). Seeds are also dispersed by water and by animals, e.g. geese, that selectively feed on seed capsules (Prop et al. 1984).

Comparison

The three yellow-flowered Saxifragas of Svalbard are rather different. Saxifraga platysepala is distinguished from the two others by its long, above-ground runners (stolons) ending in small rosettes (the "Spider Saxifrage") and by being glandular pubescent. Saxifraga aizoides and S. hirculus are distinguished by the former having ciliate leaves, small and often several flowers per stem, and by sepals appressed or patent in late flower and fruit stages; the latter having entire leaves, large and mostly single flowers, and by sepals deflexed in late flower and fruit stages.

Habitat

Most frequent on gravel and sand periodically inundated from lakes, rivers or brooks and on gravel slopes with seepage. Prefers coarse and well-drained substrates. Perhaps restricted to substrates with a circumneutral to basic soil reaction with pH 6.5 or higher (Elvebakk 1982).

Distribution

Frequent in the middle arctic tundra zone, less frequent in the northern arctic tundra zone. Present in all sections. Restricted to Spitsbergen, Prins Karls Forland, and Bjørnøya, and predominantly in areas with circumneutral or basic bedrock.

The general range is European and North American, in the arctic and northern boreal zones and in the alpine belts. The species is present in Europe east to the Urals and south to the S European mountains, in the North Atlantic islands, Greenland, and in North America west to Yukon and the Rocky Mountains.

Comments

Saxifraga aizoides is morphologically uniform in Svalbard, whereas it is polymorphic, at least in flower colour, in mainland N Europe. The petals of mainland plants vary between bright yellow (with or without darker dots), reddish yellow with red dots, and purple, with associated darker coloration of sepals, stamens and fruits. The Svalbard plants have uniformly bright yellow petals without prominent darker dots. The flowers are also uniformly smaller than in mainland plants, with shorter (and thereby relatively broader) sepals and petals, and with shorter, subentire leaves. The mainland morphs are widely distributed in Europe, whereas the Svalbard morph is the one found in Greenland and arctic Canada. No investigation of this variation has been undertaken.

Literature

Alsos, I.G, Müller, E. & Eidesen, P.B. 2013. Germinating seeds or bulbils in 87 of 113 tested Arctic species indicate potential for ex situ seed bank storage. – Polar Biology 36: 819–830. Doi 10.1007/s00300-013-1307-7.

Brochmann, C. & Steen, S.W. 1999. Sex and genes in the flora of Svalbard - implications for conservation biology and climate change. – Det Norske Videnskaps-Akademi. I. Matematisk Naturvitenskapelig Klasse, Skrifter, Ny serie 38: 33–72.

Elvebakk, A. 1982. Geological preferences among Svalbard plants. – Inter-Nord: 11–31.

Prop, J., van Erden, M.R. & Drent, R.H. 1984. Reproductive success of Barnacle Goose Branta leucopsis in relation to food exploitation on the breeding grounds, western Spitsbergen. – Norsk Polarinstitutts Skrifter 181: 87–117.

Savile, D.B.O. 1972. Arctic adaptations in plants. – Canada Department of Agriculture Research Branch Monograph 6. 81 pp.