Life span

Perennial, not very long-lived.

Growth form

Solitary herb with a vertical, branched subterranean stem (caudex). Flowering stems single or numerous (sometimes 10 or more) in each plant, 5–10(12) cm, erect, simple. Stems, stem leaves, and calyces with long, articulate hairs with dark violet dividing walls (making the hairs appear violet), and many hairs gland-tipped.

Leaf

Leaves opposite, entire. Basal leaves (1.0)1.5–3.0 × 0.2–0.5 cm, in 2–3 pairs, narrowly oblanceolate or spathulate, ciliate with very short hairs, green or tinged with dark violet. Stem leaves in 2–3 pairs, narrower than basal leaves, the uppermost pair very reduced.

Inflorescence

Inflorescence of a single terminal flower, very rarely 2–3 in a reduced dichasial cyme, if more than one with reduced bracts. Flowers nodding in flowering stage but become strictly erect after pollination is accomplished.

Flower

Flowers radially symmetric with 5 sepals and petals. Calyx of fused sepals with short, pink to lilac calyx lobes, in flower stage ca. 1.5 times as long as broad and inflated, in fruit stage becoming more inflated and bladder-like, ca. 1–1.5 × 1–1.5 cm, about as broad as long or even broader, greyish to pale violet with ca. 10 rib-like, dark violet veins. Petals free, emerging ca. 0.5 cm from calyx, irregularly bifid, lilac or greyish violet. Stamens 10, enclosed. Gynoecium of three fused carpels with three stigmas, with one room.

Fruit

Fruit an erect capsule opening at top with 10 lobes. Seeds numerous, brown, 1.4–2 mm, with broad wing ca. 0.6 mm wide.

Reproduction

Sexual reproduction by seeds; no vegetative reproduction. Flowering period prolonged, from late June to August. The nearly closed flower with only slightly emerging petals and fully enclosed stamens suggests a high level of self pollination in this species and subspecies, even if its relatives (e.g., Silene involucrata) are much more adapted to insect pollination. A high number of seeds are produced, a sign of self pollination. Nevertheless, a few hybrids with S. involucrata are reported from Svalbard, sure signs that some cross fertilization takes place. The seeds ripen regularly, and they germinate to 30–100 % at 18–20ºC, and about 5 % under outdoor conditions (Alsos et al. 2013, Müller et al. 2011). Seed weight is 0.008 g/50 seeds (Alsos et al. 2013).

The seeds have wings and are therefore adapted to wind dispersal along the ground (they are too large and heavy to fly high). The stems become very stiff in autumn. The combination of stiff stem, erect capsule and apical capsule teeth assure that dispersal only takes place when the wind speed is above a certain level (or when moved by an animal) assuring initial spread of seeds at some distance from the mother plant.

Comparison

The only plant similar to Silene uralensis in Svalbard is S. involucrata. When in flower, they differ several characters: In S. uralensis the petals emerge only a small distance from the calyx and are lilac and fringed, and the flowers are nodding (but erect after flowering), and the calyx is larger and broader, especially in the fruit stage where it becomes globular or broader than high; in S. involucrata the petals emerge up to 0.5 cm from the calyx and are white and regularly notched, the flowers are erect, and the calyx is smaller and not nearly as broad.

Even if both species have abundant glandular hairs, S. involucrata is much more sticky than S. uralensis. Dust and dirt fragments are often attached to the stems and leaves of S. involucrata, rarely to those of S. uralensis.

Habitat

Most common in moderately moist heaths and meadows, shallow mires, along water-courses, and in moderate snowbeds. On moderately drained, mixed or fine textured soils with weakly acidic or basic soil reaction (pH). Requires a minimum of snow protection during winter but young individuals often found on quite exposed sites. Inflorescence and stem probably grazed by reindeer, fruits also by snow bunting and perhaps ptarmigan.

Distribution

Present in all zones and sections. Widely distributed in the Spitsbergen islands but not observed from the areas south of Van Mijenfjorden or from the most acidic areas in the northwest. Not reported from Bjørnøya.

The general range of Silene uralensis ssp. arctica is circumpolar in the arctic zones. See Comments for ranges of the other subspecies (ssp. uralensis) and a related species (S. wahlbergella).

Comments

Elven et al. (2011) argued that there are disjunct morphological differences between the arctic circumpolar Silene uralensis ssp. arctica, the Scandinavian S. wahlbergella, and the boreal to arctic, nearly circumpolar S. uralensis ssp. uralensis. The ranges of S. uralensis ssp. arctica and S. wahlbergella do not overlap (they are allopatric), and no morphological transition is known. The ranges of ssp. arctica and ssp. uralensis do, however, overlap in several regions (they are parapatric), at least in the northernmost Urals and Vaigach island, in arctic Canada, and in Greenland. Even here, the two plants appear as morphologically distinct, a few times in mixed stands. Taxonomic rank may therefore be debatable, as subspecies (due to morphological similarity and parapatric ranges) or as species (due to discontinuous morphological differences in spite of overlap). Lack of transitional plants or populations may, however, partly be due to the assumed predominant self-fertilization.

Some authors have argued that ssp. arctica is restricted to Svalbard, whereas the arctic plants elsewhere belong to ssp. uralensis (e.g., Bocquet 1967). We have compared plants from Svalbard with specimens from Greenland, Canada, Alaska, and Russia and find no differences whatsoever.

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.

Bocquet, G. 1967. Physolychnidium olim Gastrolychnidium nomenclaturae fundamentum includens combinationes taxaque nova nonnulla Silenes generis. – Candollea 22: 1–38.

Elven, R., Murray, D.F., Razzhivin, V. & Yurtsev, B.A. (eds.) 2011. Annotated Checklist of the Panarctic Flora (PAF).

Müller, E., Cooper, E.J. & Alsos, I.G. 2011. Germinability of arctic plants is high in perceived optimal conditions but low in the field. – Botany 89: 337–348.