Poa arctica R. Br. subsp. arctica
Chlor. Melvill. 30. 1823.
Type: Canada. Melville Island, Mr. J. Edwards on W.E. Parry's first voyage, 1819–1820. (Holotype: BM! Isotype: LE, Tzvelev (1976)).
Plants caespitose, or not caespitose (new branches arising extra-vaginally, occasionally intravaginally); with unbranched stems in loose clusters, or tufted in some habitats.; less than 15 cm high, or more than 15 cm high; (7.5–)10–30 cm high. Ground-level or under-ground stems horizontal, or not developed horizontally or vertically at, on, or below, the ground (very occasionally); rhizomatous; elongate, or compact; 1 mm wide. Scales present; striate. Aerial stems decumbent (usually, leafy for approximately half their length); glabrous. Leaves mostly in a basal tuft. Prophylls 0.5 mm long (in extra-vaginal branches). Sheaths with the margins fused only in the lower part; glabrous. Ligules (1–)1.5–3.5(–4) mm long; membranous; glabrous; ovate-oblong to transversely oblong; apices obtuse, or truncate; entire, or erose, or lacerate. Blades 20–310 mm long; 0.8–1.5 mm wide (to 2.5 mm when flat); spreading; folded in bud; flat, or folded; midvein conspicuously larger than the lateral veins; bulliform cells in distinct rows on either side of the midvein. Blades adaxial surface hairy. Blades abaxial surface glabrous.
Flowering culm nodes not exposed, or becoming exposed; number visible 0–1. Inflorescence paniculate; diffuse; pyramidal, rather open, spikelets characteristically congregated towards the ends of the branches, borne at right angles to the rachis, or drooping, illustrated in database; 2–9.5 cm long; 10–40(–75) mm wide. Inflorescence. Inflorescence main axis glabrous, or scabrous (sometimes, near apex). Number of inflorescence branches at lowest node 1–2(–3). Inflorescence primary branches (4–)6–20(–26) mm long; glabrous (usually), or scabrous (sparsely so); with appressed secondary branches. Spikelets. Spikelets pedicellate; disarticulating above the glumes; laterally compressed; ovate; 4.4–6.6 mm long; 2.5–4 mm wide. Florets per spikelet (2–)3–4(–6). Glumes. Glumes unequal, the second almost twice as wide as the first, weakly keeled. First glume 0.7–0.9(–1) × the length of the second glume (equal to sub-equal in length, unequal in width); 0.6–0.8 × spikelet length; 3–5 mm long; lanceolate; glabrous; margins glabrous; veins 1–3; apex acuminate (a contrast with P. pratensis subsp. alpigena). Second glume 0.4–0.9 × as long as the spikelet; almost as long as, or longer than, the lowest floret; lanceolate, or ovate; 3.5–5 mm long; glabrous; veins 3. Rachilla internode 1 mm long (approximately); glabrous. Rachilla not pronounced between the florets; extending beyond the uppermost floret. Callus differentiated (web either a small tuft of curly hairs or well developed); hairs shorter than the floret. Lemmas. Lemma (3.3–)3.8–5.2 mm long; ovate; keeled; surface dull (margins thinner in texture than the body of the lemma); surface hairy; surface with trichomes on and between the veins (particularly on the keel an marginal vein, but mostly with appressed short hairs between the veins, lanate at the base); veins 5 (not reaching to the apex). Lemma apex acute; entire; awnless. Palea well developed; 3.5–4.5 mm long; with hairy veins (the hairs particularly long towards the middle, and pilose between the veins especially in the lower 1/2, a key distinction between P. arctica and P. pratensis s.l.). Perianth reduced to lodicules. Anthers 1.2–2.5 mm long. Styles 2. Fruit sessile. Fruit dry; indehiscent. Fruit 2–2.5 mm long. Seeds 1.
Chromosome information. 2n = 72 and 76.
Distribution. Circumpolar. High arctic. Range in the Canadian Arctic Archipelago widespread. Arctic Islands: Baffin, Devon, Ellesmere, Axel Heiberg, Parry Islands, Cornwallis, Banks, Victoria, Prince of Wales, Somerset, King William, Southampton (Ellef Ringnes).
Ecology and habitat. Substrates: wet meadows (where they form raised clumps), hummocks (of Poa arctica plants), along streams, tundra, slopes, ridges, seashore (above tidal influences), dry meadows; imperfectly drained moist areas, on solifluction slopes, dry, moderately well drained; acidic (granite outcrops), or calcareous (disintegrated limestone); rocks, gravel, sand, silt, clay, moss. Habitats: Occurring on moderately to imperfectly drained gravel, on soils adjacent to wetlands, and on raised mossy hummocks in wet meadows, where it often adopts a tufted form (latter observation Gillespie, Soreng & Consaul 1999). It is often an early coloniser of disturbed habitats.
Notes. A widespread, relatively distinct species, Poa arctica is considered highly polymorphic (Tzvelev 1976; Edmonson 1980). Tzvelev (1976) claimed that it is probably represented in the former Soviet Union by several, still unidentified subspecies with different chromosome numbers. In Svalbard and Northern Norway proliferating and non-proliferating entities are about equally frequent and the non proliferating ones seem to be highly agamospermic, often with shrivelled anthers and undeveloped pollen (see also Taxonomic Notes for P. arctica subsp. caespitans).
Tzvelev (1976) commented that the rarely found viviparous variety, var. vivipara Hook. is probably the hybrid between P. arctica × pratensis s.l., which is not always distinguishable from some forms of P. pratensis subsp. colpodea Tzvelev. Porsild (1957, 1964) and Porsild and Cody (1980) mapped P. arctica var. vivipara in 18 different localities throughout the Eastern Arctic. We have not been able to verify any of these records. Upon examination of herbarium specimens at CAN and DAO, none were located at CAN, while the several specimens found at DAO were redetermined as P. pratensis subsp. colpodea. Gillespie and Boles (in press) note that Porsild (1957, and also in Porsild and Cody 1980) appears to have reidentified collections of P. pratensis subsp. colpodea as P. arctica var. vivipara, following his earlier comment (1955) regarding most viviparous High Arctic Poa as best placed in P. arctica as var. vivipara, but unfortunately provides no explanation. Based on their (Gillespie and Boles) recent examination of field and herbarium specimens and our present understanding of arctic Poa taxa, it appears that P. arctica var. vivipara is not present on the Canadian Arctic Islands.
Illustrations. • Habitat. Densely clumped plants forming low broad mounds in a wet hummocky meadow at the base of a glacier, ~450 m elevation. Nunavut, Axel Heiberg Island. Large valley along upper Bukken River, 80°31.57'N, 92°21.83'W.. L.J. Gillespie. 6619, L.L. Consaul & R.J. Soreng. CAN. • Habitat and Close-up of plant. Small wet mossy meadow on barren scree slope, ~600 m. Tufted or densely turfy plants forming low circular mounds. Nunavut, Ellesmere Island, Sawtooth Range, W side, 79°43.54'N, 83°09.44'W. 5 August 1999. L.J. Gillespie 6647, L.L. Consaul & R.J. Soreng. CAN. • Close-up of plant. Plants with short flowering culms growing in low mounds. Nunavut, Baffin Island, Nanisivik Airport, 73°02'N, 84°33'W. Moist stony plateau near airport entrance. 9 August 1999. L.J. Gillespie. 6690, L.L. Consaul & R.J. Soreng. CAN. • Laboratory photograph of whole plant. Nunavut, Baffin Island, Iqaluit, plant in laboratory setting showing inflorescence branches at right angles to the main rachis, Aiken 94–020. (CAN). Photograph by K. Clarkin. • Laboratory photograph of plant habit. Nunavut, Baffin Island, laboratory photograph of plant habit showing loose culms developing from rhizomes. L. Gillespie. Photograph by K. Clarkin, August 1994. • Close-up of inflorescence. Spreading inflorescence with few spikelets borne towards the ends of the branches. Nunavut, Baffin Island, Iqaluit, Aiken 94–020. CAN. Scale bar in cm. Photograph by K. Clarkin. • Close-up of small inflorescence. Note the delicate inflorescence with one or two spikelets per branch. Nunavut, Baffin Island. Photograph by K. Clarkin, August 1994. Scale bar in cm. • Holotype specimen. Poa arctica. Melville Island, 1819–1820, Mr. J. Edwards on W.E. Parry's on his first voyage. (Holotype: BM). Other text on label: "Poa arctica R. Br. in Parry, Journ. Voy. Discov. NW Pass. Suppl. 288 (1924)". • Comparison photo with Poa glauca. Laboratory photograph of inflorescences showing drooping branches of Poa arctica (slightly atypical, but with typically large spikelets) on the left, more typical horizontal branches of Poa arctica on the right, and the erect branches of Poa glauca that have relatively smaller spikelets in the centre. Plants collected Nunavut, Baffin Island. Photograph by K. Clarkin. • Distribution map.
Cite this publication as: ‘S.G. Aiken, L.L. Consaul, and M.J. Dallwitz. 1995 onwards. Poaceae of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 10th December 2001. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980), Dallwitz, Paine and Zurcher (1993, 1995, 2000) , and Aiken, Dallwitz et al. (1999) should also be cited (see References).
