Life span

Perennial, moderately long-lived.

Growth form

Solitary herb, often in small tussocks with small lateral shoots from the vertical main caudex. These shoots may become independent of the mother plant but only at a very short distance (1 cm). Stems erect, to 12–15 cm, singly from each shoot, but up to 12 stems observed on one individual. Leaves crowded at the base and on the lower part of the stems. Stems, leaves, and phyllaries with long, articulate hairs.

Leaf

Leaves alternate. Basal leaves 4–5 cm, oblanceolate or narrowly oblanceolate, glabrous or sparsely pubescent, obtuse. Stem leaves 1–5 cm, linear or narrowly oblanceolate, acute, densely villous with white, shiny hairs.

Inflorescence and Flower

The primary inflorescence of Asteraceae is a head (capitulum) surrounded by an involucrum of one or more rows of phyllaries (involucral bracts). The flowers sit on a flat, concave or convex receptacle, sometimes with scales (the bracts of the single flowers). The flowers are epigynous with perianth at top of the gynoecium. The sepals are always transformed into a pappus, mostly by hairs or sometimes by scales. The 5 stamens are inserted in the corolla tube and the anthers form a ring through which the style grows and pushes the pollen outwards. Gynoecium of two fused carpels, 2 stigmas. The fruit is an achene with one seed.

Inflorescence a single head terminally on each stem. Involucrum rounded to truncate at base. Phyllaries in several rows, strongly spreading, 0.7–1 cm, lanceolate, densely pubescent with white, shiny articulate hairs; some hairs with purple cell walls may occur. Marginal flowers monosymmetric, female, with corolla ligulate (all petals fused into a ligula facing outwards, with ca. 3 indistinct teeth at apex), (4)5–6 mm, white or pale purple. Central flowers radially symmetric, bisexual with corolla tubular and yellow.

Fruit

The fruit is an achene with pappus of numerous white, dentate hairs. Numerous fruits from each head.

Reproduction

Sexual reproduction by seeds; no vegetative reproduction. Flowers are adapted to insect pollination and outcrossing. Mature fruits have been observed on herbarium specimens from the Isfjorden area, and specimens from the Wijdefjorden area had last year's stem with all fruits shed (R. Elven observ. 2010), indicating that they set ripe fruits. This, together with the local distribution as populations rich in individuals, suggests that seed recruitment takes place regularly.

Fruits are adapted to wind dispersal due to their pappus but probably not for very long distances.

Comparison

The two species of Erigeron in Svalbard differ in several features: Erigeron eriocephalus is taller, has an involucrum broadly subglobular and with strongly spreading phyllaries, and the hairs on the phyllaries and the upper parts of the stem are mostly white; E. humilis is much more short-grown, has an involucrum more narrowly cuneate with appressed phyllaries, and the hairs on the phyllaries and the upper parts of the stem are purple-walled.

Habitat

Only found on steep slopes with a southern or western exposure and on some nunataks, there probably also on slopes with enhanced insolation due to reflection from the surrounding glacier. On open calcareous loam and other fine-grained substrates. Co-occurs at some places with Trisetum spicatum, indicating that it demands some snow cover.

Distribution

Recorded from the middle and the northern arctic tundra zones and from a single locality classified as in the polar desert zone but in a site with assumed locally high summer temperature due to high insolation and wind shelter. From the transitional to the clearly continental section. All records are from N Spitsbergen, north of Isfjorden, and from a single site in NW Nordaustlandet (Depotodden in Brennevinsfjorden, Gustav V Land). The Spitsbergen records are from James I Land: Blomesletta at Isfjorden and Palasset, a nunatak between Isfjorden and Kongsfjorden; Andrée Land: Malafjell—Landgangsdalen and Purpurdalen at the west side of Wijdefjorden; and Ny-Friesland: Sørbreen, Flatøyrdalen and Ringhorndalen at the east side of Wijdefjorden and near Vaigattbogen on the northeast coast of Spitsbergen.

The general range is probably circumpolar in the arctic zones, perhaps transgressing to mountains in the boreal zones. See Comments.

Comments

Erigeron eriocephalus is closely related to and at the same ploidy level (diploid) as the European E. uniflorus. These two are often considered subspecies or varieties of one species (E. uniflorus) due to transitional forms found in the Scandinavian mountains and perhaps in Iceland (e.g., Lid & Lid 2005; Nesom 2006). Hultén & Fries (1986) considered E. uniflorus s. str. to be restricted to the C European mountains, whereas they assigned all northern plants to their ssp. eriocephalus. This was obviously wrong as no difference has been found between Alpine and Scandinavian E. uniflorus but several differences between Scandinavian E. uniflorus and arctic E. eriocephalus. At a global scale, the two are rather different and the Scandinavian plants assigned to E. eriocephalus may be transitional. Ecologically, the two differ. Erigeron eriocephalus is a plant of sunny, dry sites; E. uniflorus a plant of moist snowbeds.

Literature

Hultén, E. & Fries, M. 1986. Atlas of North European Vascular Plants North of the Tropic of Cancer. – Königstein: Koeltz Scientific Books.

Lid, J. & Lid, D.T. 2005. Norsk flora. Ed. 7 by R. Elven. – Det Norske Samlaget, Oslo.

Nesom, G.L. 2006. Erigeron Linnaeus. – In: Flora of North America Editorial Committee, eds., Flora of North America north of Mexico. 20. Magnoliophyta: Asteridae (in part): Asteraceae, part 2: 256–348.