Life span

Perennial, moderately long-lived.

Growth form

Solitary herb with subterranean, simple or more rarely branched caudex, leaves in one or more rosettes at end of caudex branches. Flowering stems (scapes) up to 30 cm, stout and stiff, 2.5–4 mm thick, densely glandular-pubescent with articulate hairs.

Leaf

Leaves alternate, all in basal rosettes, 2–7 cm long, ovate or elliptic, gradually narrowing towards a broad petiole, acute, shallowly crenate or dentate, sparsely pubescent on both sides, more regularly pubescent along margins, hairs articulate.

Inflorescence

Inflorescence a very compact, spike-like panicle of numerous clusters of subsessile flowers. Bracts large and leaf-like.

Flower

Flowers radially symmetric with 5 free sepals and petals. Sepals 1–2 × 1–2 mm, broadly triangular, deflexed in fruit, green or with red margins. Petals 1–2 × 0.6–1.4 mm, about the length of the sepals or shorter, narrowly ovate or oblong, purplish. Stamens 10. Gynoecium semi-inferior, of two fused carpels split apically and with 2 styles.

Fruit

Capsule with numerous seeds.

Reproduction

Sexual reproduction by seeds; no vegetative dispersal. Flowers are adapted to insect pollination with a disc between stamens and gynoecium. The flowers are, however, very small and probably mainly self-pollinating. Flowering is regular but fruits often abort, suggesting that seed-set fails in many seasons. However, the species depends on seed-set for propagation. Germinability of seeds is 43 % (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 animals, e.g., geese that selectively feed on capsules (Prop et al. 1984).

Comparison

Tall-grown Micranthes nivalis is sometimes mistaken for M. hieraciifolia (or for the not confirmed hybrid M. hieraciifolia × nivalis). However, M. hieraciifolia differs from M. nivalis in numerous features, foremost the very small and deep red petals and the broadly triangular sepals, but also leaf shape, the stout flowering stems, and the elongated, interrupted inflorescence with several clusters of flowers.

Of the four species of Micranthes in Svalbard, M. foliolosa and M. hieraciifolia are easily separable from the two others and from each other even by their leaves. Micranthes foliolosa has characteristic, obovate or obcuneate leaves with a few triangular teeth in the distal 1/3 only, and the leaves are thin and glabrous; M. hieraciifolia has ovate or lanceolate, subacute or acute leaves with sparse, shallow teeth along the sides, and the leaves are thick and with white, articulate hairs along the margins and on the lower surface. Micranthes nivalis and tenuis both have thick, rounded leaves with obtuse, forward pointing teeth and are less readily recognized (see these species).

Habitat

Dense moist heath and meadow vegetation, vegetated patterned ground, the driest parts of mires. Clearly preferring moist, fine-grained substrates with more or less impeded drainage. On substrates with circumneutral to basic soil reaction (pH).

Distribution

Common in the middle arctic tundra zone, more sparse in the warmer parts of the northern arctic tundra zone. In the transitional to clearly continental sections. Mainly on Spitsbergen with two finds on W Edgeøya, one on NW Nordaustlandet, and a few on N Prins Karls Forland.

The general range is circumpolar and arctic–alpine but disrupted; the species is, e.g., very rare in Greenland (only in the east). The southern limit in Europe is in the Carpathian Mountains (relict, nearly extinct).

Comments

Micranthes hieraciifolia is monomorphic in Svalbard but not elsewhere. Two races have been proposed, a circumarctic ssp. hieraciifolia also reaching southwards to C Europe, and a Beringian ssp. longifolia (Engl. & Irmsch.) Elven & D.F.Murray (= ssp. czukczorum Chrtek & Soják) at a lower ploidy level (see Elven & Murray 2008; Elven et al. 2011). Subspecies hieraciifolia may have derived from a hybrid or introgression between ssp. longifolia and some other species of Micranthes present in the Beringian regions. In a phytochemical investigation of European Saxifraga (s. lat.) species, Andersen & Øvstedal (1988) found M. hieraciifolia to have a different and complicated pattern in anthocyanins compared with the other investigated Micranthes species (M. foliolosa, M. nivalis, M. stellaris, M. tenuis) which all had a similar and very simple pattern.

Hybrids between M. hieraciifolia and M. nivalis have been reported, also from Svalbard. The material we have inspected of such proposed hybrids has been misidentified, either tall-grown M. nivalis or small-grown M. hieraciifolia. We have not seen any convincing specimen of this hybrid, neither from Svalbard nor from anywhere else.

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.

Andersen, Ø.M. & Øvstedal, D.O. 1988. Anthocyanin patterns of European Saxifraga species. – Biochemical Systematics and Ecology 16: 545–550.

Elven, R. & Murray, D.F. 2008. New combinations in the Panarctic vascular plant flora. – Journal of the Botanical Research Institute of Texas 2: 433–446.

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

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.