Arctophila fulva

GROWTH FORM

Graminoid forb growing in extensive mats due to stout (3—5 mm broad), whitish, branched rhizomes, typically with branches of 5—15(30) cm between aerial shoots. Rhizome branches abundantly rooting at all nodes (at base of aerial shoots and between these). Aerial shoots ascending from rhizome, at base with several prophylls (reduced leaves without or only with a short blade). Base of culms with some withered leaf remains but no distinct sheaths. Culms 10—20(30) cm, erect, smooth and glabrous. A few stands regularly observed with flowering shoots but many others with only leafy shoots.

LEAF

Leaves flat but involute towards apex, with numerous veins raised on both surfaces, mid vein slightly broader than the other veins; both surfaces densely papillose along veins. Vegetative shoots with leaf arrangement conspicuously distichous; leaves are crowded and pointing to opposite sides, making these shoots unique in appearance among Svalbard grasses, a feature only partly shared by the hybrid species Arctodupontia scleroclada. Leaves of vegetative shoots up to 32 cm long, often much longer than culms of reproductive shoots, in many stands very broad (4—9 mm), in others more narrow (2—4 mm), tapering evenly towards apex. Typically, leaves on floating shoots are narrower than on aerial shoots. Culm leaves (3)4—5, similar to leaves of vegetative shoots but usually much shorter, blades 3—8(9) cm, flag leaf blade attached above middle of culm. Ligula 2—4(5) mm, more or less truncate, deeply lacerate.

INFLORESCENCE AND FLOWER

The units of the inflorescence of Poaceae are the spikelets, nearly always numerous in a panicle or spike-like inflorescence. Spikelets are composed of 2 glumes (bracts for the spikelet) and one or more flowers (the term used below) or rather floral units, often named ‘florets’ because we do not know what is the exact flower. A flower or floret is composed of a lemma with one mid vein (probably the floral bract), a palea with 2 mid veins (either fused bracteoles or perhaps 2 fused perianth leaves), 3 small organs called ‘lodiculae’ and essential in the opening of the flower at anthesis (possibly transformed perianth leaves or transformed stamens), 3 stamens (mostly), and a gynoecium of 2 fused carpels with 2 feathery stigmas and one seed.

Inflorescence an open, broadly pyramidal panicle, 3.5—7 × 3—6 cm, with patent to pendulous branches, occupying 1/3—1/4 of total culm length. Panicle with (5)6—9 nodes, with (3)4—5 branches at each of the lower nodes. Panicle mid axis and branches smooth. Branches 15—25 mm, the longer ones with 3—5 spikelets, mainly towards the end of the branches. Spikelets (3.5)4—4.5 × (1.5)2—2.5 mm, oblong, with 2—3 flowers. Bracts (glumes and lemmas) with rounded backs, i.e., without a keel, with distinct mid vein and indistinct lateral veins. Glumes differ in length: lower glume (1.5)2—2.5(3) mm, upper glume (2.5)3—3.5(4) mm, more than 1/2 the length of the spikelet, both glumes ovate or obovate, obtuse or acute or with a short, extended tip, variegated in violet near base, bronze yellow and white near tip and in margin, smooth and glabrous. Lemmas (2.5)3—3.5(4) mm, ovate, obtuse or subacute, sometimes lacerate, with the same colour pattern as glumes, smooth and glabrous. Paleas narrower and shorter than lemmas, smooth on keels. No stamens observed by us in the field in Svalbard or in the Svalbard herbarium material. Anthers otherwise reported to be 1.2—3 mm (Cayouette & Darbyshire 2007).

FRUIT

Fruit an achene (with one seed).

REPRODUCTION

Sexual reproduction by seeds; efficient local vegetative reproduction by rhizomes. The species is assumed to have seed-set but the efficiency of seed reproduction in Svalbard is not known. This plant flowers quite late (August) and we have not observed ripe fruit (see also Alsos et al. 2013).

We assume bird dispersal of fruits (inside florets) to be the major way of dispersal into Svalbard but bird dispersal of shoot fragments to be the major way of dispersal within Svalbard today.

COMPARISON

Arctophila fulva is closely related to Dupontia fisheri, probably one of the parental genera to the assumed hybrid genus Dupontia, and the genome of Dupontia has been homogenized in the direction of Arctophila (Brysting et al. 2004; Brysting in comments in Elven et al. 2011). The two genera also produces a transgenus hybrid species: Arctodupontia scleroclada. It is often difficult to keep these three genera and species apart. Dupontia and Arctodupontia do not have the coarse, strongly distichous leafy shoots of Arctophila and never as broad leaves as Arctophila (usually 4—9 mm); however, there are narrow-leaved Arctophila, too. The glumes and lemmas of Dupontia are much longer than those of Arctophila, with extended, deeply lacerate apices. For Arctodupontia scleroclada, see that species.

The broad, open panicle of Arctophila may resemble that of some Poa species but the leaves are markedly different: in Arctophila leaves are not keeled but in a dense distichous arrangement on shoots; in Poa leaves are distinctly keeled but rarely in distichous arrangement (the main exception being P. alpina). Also the keeled backs of glumes and lemmas in Poa contrast with the rounded backs in Arctophila. No species of Poa grows as wet as does Arctophila fulva.

HABITAT

Arctophila fulva is always rooted in permanently wet or submerged fine substrates and may form dense swards with innumerable leafy shoots, but often very few flowering shoots, or it has leaves floating on the water (and then usually not flowering). It is indifferent as to soil reaction (pH) but melt water from the permafrost furnishes the wetlands with minerals and ions all summer. The species is found both in calm and slowly running water.

DISTRIBUTION

Distributed in the middle and northern arctic tundra zones and the weakly oceanic to weakly continental sections. The species is locally common in the wetlands of Bjørnøya where it is recorded from 14 sites but only found flowering two times (Engelskjøn & Schweitzer 1970). On Spitsbergen there are numerous recorded sites along the west coast and fjords from Sørkapp Land in the south to Liefdefjorden in the north but no records from the Wijdefjorden area or from the east coast. The species is not recorded from any of the other islands in the Spitsbergen group.

Arctophila fulva is one of the ecologically most important wetland vascular plant in the Arctic. It is the major constituent of nearly all larger arctic swamps in NE Europe, N Asia and N North America, also in the northern boreal zone. It is very rare in Greenland and in NW Europe. It has long been known from the Bothnian Bay and the Torniojoki valley in N Sweden and Finland but has comparatively recently also been found in single sites in, respectively, Finnmark in N Norway (in 1980; see Elven & Johansen 1981) and Oppland in S Norway (in 2012; see Elven & Fremstad 2012), in both cases suspected to result from fortuitous long-distance bird dispersal (see Elven et al. 2013).

COMMENTS

Arctophila fulva is the only accepted species in its genus but quite polymorphic. It is hexaploid (2n = 42; Elven et al. 2011) and is probably of hybrid origin. The plants on the European mainland in Fennoscandia and in Russia south of the Arctic are often quite tall (100 cm or more) and with a large, pendulous panicle (var. pendulina (Laest.) Holmb., described from the Torniojoki valley along the border between Sweden and Finland). Most people would not recognize them as belonging to the same species as the low-grown Svalbard plants. Plants from arctic Russia are distinctively more low-grown, similar to the plants in Svalbard, and have been described as ssp. similis (Rupr.) Tzvelev (from the arctic island of Kolguev). There are no recent morphological studies of the variation in this species, nor genetic studies, i.e., no consistent support yet for recognition of races. However, the morphological differences between the plants of N Fennoscandia and those of Spitsbergen and Bjørnøya prevent us from assuming a bird dispersal route for this species in that direction. The rareness in Greenland makes dispersal to Svalbard from the west unlikely. The remaining possibility is a dispersal connection between Svalbard and the N Russian areas (i.e., ssp. similis).

Some of the plants on Bjørnøya are unusually coarse, much coarser than anything on Spitsbergen, and resemble the plants on the mainland in N Russia (e.g., the Ponoj area on Kola Peninsula). These may have come to Bjørnøya from another source area than the plants in Spitsbergen and the majority of Bjørnøya plants.

In a recent study (Tkach et al. 2020) Arctophila is merged within Dupontia as D. fulva Röser & Tkach. If this approach is followed, also Arctodupontia with A. scleroclada must be included, as Dupontia scleroclada (Rupr.) Rupr.

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.

Brysting, A.K., Fay, M.F., Leitch, I.J. & Aiken, S.G. 2004. One or more species in the arctic grass genus Dupontia? – a contribution to the Panarctic Flora project. – Taxon 53: 365–382.

Cayouette, J. & Darbyshire, S.J. 2007. Arctophila (Rupr.) Andersson. – In: Flora of North America Editorial Committee (eds.), Flora of North America north of Mexico. 24. Magnoliophyta: Commelinidae (in part): Poaceae, part 1: 605–607.

Elven, R. & Fremstad, E. 2012. Hengegras Arctophila fulva funnet i Sør-Norge. – Blyttia 70: 237–243.

Elven, R., Fremstad, E. & Pedersen, O. (eds.) 2013. Distribution maps of Norwegian vascular plants. IV The eastern and northeastern elements. — Akademika Publishing, Trondheim.

Elven, R. & Johansen, V. 1981. Hengegras – Arctophila fulva – ny for Norge. – Blyttia 39: 27–31.

Elven, R., Murray, D.F., Razzhivin, V. & Yurtsev, B.A. (eds.) 2011. Annotated Checklist of the Panarctic Flora (PAF) Vascular plants. http://panarcticflora.org/

Engelskjøn, T. & Schweitzer, H.J. 1970. Studies on the flora of Bjørnøya (Bear Island) I. Vascular plants. — Astarte 3: 1—36.

Tkach, N., Schneider, J., Döring, E., Wölk, A., Hochbach, A., Nisen, J., Winterfeld, G., Meyer, S., Gabriel, J., Hoffmann, M.H. & Röser, M. 2020. Phylogenetic lineages and the role of hybridization as driving force of evolution in grass supertribe Poodae. – Taxon 69: 234–277.