Flora of the Canadian Arctic Archipelago


S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, L.J. Gillespie, A.K. Brysting, H. Solstad, and J.G. Harris

Poa arctica R. Br. subsp. caespitans Nannf.

English: Arctic bluegrass,

French: Pâturin arctique,

Inuktitut: Iviit, ivisuka, ivitsuskaka.

Poaceae, Grass family.

Published in Symb. Bot. Upsal. 4, 4: 71. 1940.

Type: Canada. Nunavut: Ellesmere Island, "Harbour Fjord" Simmons 4000 (UPS). Lectotype: Simmons 1906, p. 77. Isotype: O! Collections by H. G. Simmons from Ellesmere Island, no. 303 from Cape Rutherford, 78°49'N, 49°W, and no. 3641 from "Goose Fiord". CAN!

Synonymy. Poa arctica var. caespitans (Nannf.) Hylander, Uppsala Univ. Årssk. 7: 78. 1945.

Vegetative morphology. Plants 13–33 cm high; perennial herbs; caespitose (in tight coarse clumps, new shoots both intravaginal and extravaginal). Only fibrous roots present. Ground level or underground stems horizontal (short), or absent; rhizomatous; compact (if present); 0.5–0.6 mm wide. Ground level or underground stems scales present; surfaces grooved (from prominent veins); 0.5–2 mm long; glabrous. Aerial stems erect. Leaves mainly basal; alternate; marcescent. Prophylls 50–70 mm long. Petioles absent. Sheaths present; with the margins fused only in the lower part; glabrous; sheath collars present. Ligules present; 0.5–1.5 mm long (Nannfeldt's 1940 description claims up to 3 mm long, blunt and irregularly lacerate); membranous; glabrous; ovate-oblong, or transversely oblong. Ligule apices acute, or obtuse; entire. Leaves grass-like. Blades 20–60 mm long (dull dark green or purple), 0.5–0.8 mm wide (when folded; 0.8–1.4 mm when flat), appressed to the stem (the flag leaf tapering from a broad base towards a hooked, scabrous tip), folded in bud, linear, flat (rarely) or folded (usually), veins parallel, midvein similar in size to other veins in the leaf, bulliform cells in distinct rows on either side of the midvein (only conspicuous in wider, flat leaves). Blade adaxial surface hairy (sometimes puberulent). Blade abaxial surface glabrous.

Reproductive morphology. Flowering stems circular or oval in cross section. Flowering stems with leaves; culm nodes becoming exposed; culm nodes number visible 0–1. Flag leaf sheaths not inflated. Inflorescences paniculate; diffuse; pyramidal (pyramidal, with 1–3 spikelets towards the ends of the branches); 3–6.5 cm long; 30–40 mm wide. Inflorescences main axis glabrous. Number of inflorescence branches at lowest node 1–3(–5). Inflorescence primary branches 7–20 mm long; glabrous, or scabrous; with spreading secondary branches. Spikelets disarticulating above the glumes; ovate; 5.7–6.7 mm long; 2–4 mm wide. Florets per spikelet 2–4. Two glumes present. First glume 0.8–0.85 × the length of the second glume; 0.5–0.55 × spikelet length; 2.8–4 mm long; lanceolate; glabrous; margins glabrous; veins 3; apex acute. Second glume 0.4–0.9 × as long as the spikelet; almost as long as, or longer than, the lowest floret; 3.6–4.5(–4.9) mm long. Second glume oblanceolate (conspicuously wider than the first glume). Second glume glabrous; veins 3. Rachilla not pronounced between the florets; extending beyond the uppermost floret; internode 1–1.3 mm long (0.6–0.7 mm, Nannfeldt (1940)); internode glabrous. Callus differentiated (as a web reduced to a small tuft of curly hairs); hairs 1.5–2 mm long; hairs shorter than the floret. Lemma oblanceolate; 3.7–4.7(–5.3) mm long; keeled; surface dull (often blackish purple, except for a narrow margin and the tip that is hyaline with a golden-bronze colored, lacerate zone below the apex); surface hairy; surface with trichomes on and between the veins (the proximal five-eighths of the keel and the basal part of the marginal veins to about two-fifths of the length of the lemma are covered by appressed shiny, rather short (about 0.6 mm long) silky hairs; and in between, similar but very short hairs; the apical part of the lemma is glabrous. The hairs develop slowly and do not reach their definite shape and size until anthesis, before which the spikelets may look glabrous, for the keel and basal parts where the hairs develop first, are then hidden by the glumes); veins 5; apex acute; apex erose; awnless. Palea well developed; 3.5–4 mm long; veins hairy. Flowers bilaterally symmetrical (zygomorphic). Perianth represented by lodicules. Stamens 3. Anthers 1.6–2 mm long (when fully developed; often infertile anthers 1–1.3 mm present). Ovary superior; carpels 3; syncarpous. Ovaries glabrous. Styles 2. Placentation basal. Ovules per ovary 1. Fruit sessile; dry; a caryopsis; indehiscent. Seeds 1.

Chromosome information. 2n = 56.

2n (8x) = 56. Flovik (1938, 1940, Svalbard); Nannfeldt (1940); Nygren (1950a, 1950b, 1954a); Holmen (1952, Greenland); Löve (1981b, northern Canada, as P. tolmatchewii). The report in Jørgensen et al. (1958 Greenland) probably also belongs here.

Ploidy levels recorded 8x.

Taxon as an environmental indicator. The phenomenon of vegetative proliferation in grasses has been observed to be a response of plants to environmental stresses such as overwatering or overfertilising in greenhouse conditions. The first author observed proliferating inflorescences in plants growing adjacent to others with non-proliferating inflorescences after a 4-day snow storm on Melville Island (in 1985). She observed the same phenomenon at a North Yukon Dew-Line site where the plants with proliferating inflorescences were predominantly growing in the oily tracks left by a heavy vehicle crossing the tundra, while the plants with non-proliferating inflorescences were growing in adjacent less disturbed ground. Had disturbance or pollution in the environment triggered the inflorescences to proliferate? When further collections of this taxon are made in the High Arctic, very thorough habitat notes would be relevant.

Ecology and habitat. Substrates: wet meadows, hummocks (of Poa arctica subsp. caespitans plants), around the margins of ponds, marshes, along streams, river terraces, tundra, slopes, ridges, cliffs; imperfectly drained moist areas, dry, moderately well-drained areas; rocks, gravel, sand, silt, clay, moss (clumped on damp Sphagnum, CAN 258588); with high organic content (occasionally); acidic, or calcareous, or nitrophilous (owl mounds). Found in a diversity of habitats such as hummocks in stream beds, near owl perches, and on colluvial slopes. Shorter plants 10–15 cm tall grow in dry silty gravel, or peat; plants 25–35 cm tall occur in sheltered, moist, organically rich, silty sands, or marshy ground.

North American distribution. Nunavut Islands, continental Nunavut, northern Quebec. Arctic islands: Baffin, Devon, Ellesmere, Axel Heiberg, Parry islands (Melville, Prince Patrick), Victoria, Somerset, King William, Southampton (Ellef Ringnes and Salisbury).

Northern hemisphere distribution. Amphi-Atlantic. Svalbard – Franz Joseph Land, Polar Ural – Novaya Zemlya, Central Canada, Labrador – Hudson Bay, Ellesmere Land – Peary Land, West Greenland, East Greenland.

General notes. This subspecies has been recognised by Elven et al. (2003) for the Panarctic Flora and tentatively by Soreng et al. (2003) for North America. Mentioned by Porsild (1964) under species comments on P. arctica, along with comments on P. arctica var. vivipara Hooker, as a well-marked eastern arctic taxon. Tzvelev (1976), following Roshevitz (1932), suggested that this may be a hybrid between P. arctica × P. glauca. Genetically, P. arctica subsp. caespitans seems to be simpler, with fewer molecular markers, e.g., less enzyme multilocus phenotypes, at least in Svalbard (Haugen 2000), and at a lower ploidal level than most of P. arctica subsp. arctica. It seems to be constantly octoploid, whereas most voucher-supported counts of P. arctica s. str. - at least from the amphi-Atlantic areas - are at 9x or higher (Elven et al. 2003). Gillespie and Boles (2001) and Gillespie et al. (2005, and unpublished data) did not find cpDNA sequence or restriction site variation distinguishing it from subsp. arctica.

While Nannfeldt (1940) claimed that he had not seen fertile anthers in this taxon, Porsild (1964) noted that the anthers never contain good pollen. However, inflorescences on herbarium specimens from the Canadian Arctic Archipelago that are housed at CAN, and that were annotated by R.J. Soreng in 1990, have fully developed, but not necessarily fertile, anthers.

Specimens of the Canadian Arctic complex that have been called subsp. caespitans are densely tufted, only occasionally rhizomatous, with flat, soft leaves. Porsild (1964) provided distribution maps of both Poa arctica subsp. caespitans and Poa arctica var. vivipara Hooker, but did not indicate how he distinguished them. Löve and Löve (1975) followed Roshevitz (1932) and listed the taxon as having 2n = 56, on 12 counts, which contrasts with 2n = 60–88 that they give for P. arctica s.s.

The name has been put into synonomy under P. tolmatchewii Roshevitz by Tzvelev (1976), following Roshevitz (1932) who suggested that the taxon may be a hybrid P. arctica × P. glauca. In annotating specimens at CAN in 1990, R.J. Soreng, Smithsonian University, recognised P. arctica and P. arctica subsp. caespitans. In 1995, he explained that subsp. caespitans is not a well-defined taxon. It may not be diagnosable using the attributes scabrous branches and more open sheaths, but it appears to be intermediate between P. arctica and other species and may represent hybrids and the products of backcrossing.

Recent field studies (1999) have shown that there appears to be at least two densely tufted Poa taxa in the Canadian Arctic Islands. One, found in mesic stony habitats, and generally considered to be P. arctica subsp. caespitans, has mostly robust plants with broad flat leaves and often tall flowering culms. The other found in cold moist to wet areas at higher elevations has low mound-forming plants with short culms.

Haugen (2000) tested two of Tzvelev's hypotheses about the hybrid origins of taxa in Poa, using material collected in Svalbard. The entities investigated and compared in her thesis were P. abbreviata, P. alpigena viviparous type, P. alpigena subsp. colpodea, P. arctica subsp. arctica, P. arctica subsp. cespitans, P. glauca, and P. hartzii. The investigation concerned morphology (about 50 characters), biological reproductive characteristics, and isoenzymes as genetic markers. The samples of P. alpigena and P. arctica investigated were insufficiently separated in most morphological characters (except the lemma hairiness) and also less distinct in isoenzymes than would be expected of two 'species' from different aggregates. Poa arctica subsp. cespitans was slightly more distinct from P. arctica subsp. arctica in morphology than the latter was from P. alpigena. Poa arctica subsp. cespitans was also distinct enzymatically although most closely related to P. arctica subsp. arctica. Poa alpigena subsp. colpodea was fairly distinct, both morphologically and enzymatically. In morphology, it was a little more distant from 'normal' P. alpigena than the latter was from P. arctica subsp. arctica. In enzymes, however, P. alpigena subsp. colpodea was closer to P. alpigena s.s. than to P. arctica. The Svalbard plants of P. arctica subsp. arctica corresponded very well both with the type material (Melville Island) and with material collected in Melville Island in 1999. They obviously belong to the 'type' subspecies. Plants of P. arctica subsp. cespitans from Svalbard are generally morphologically quite similar to Simmons' type collections from Ellesmere Island and also to plants from Greenland named as P. arctica subsp. cespitans. Poa alpigena subsp. colpodea was described from Svalbard, and the plants Hagen (2000) investigated corresponded to the type and to plants named as such from arctic North America. What these results imply is that it is difficult to separate between the aggregates around Poa arctica and P. pratensis.

Gillespie and Boles (2001) found no evidence for P. arctica subsp. caespitans as a taxon distinct from P. arctica subsp. arctica on chloroplast DNA evidence, as individuals examined all had the same cpDNA haplotype. Nor was there evidence that it might be a hybrid between P. arctica and P. glauca either on the cpDNA evidence or from observations made during field work, but they state that further DNA studies are needed to investigate possible independent lineages suggested by morphological differences.

In northern Norway and Svalbard, P. arctica subsp. arctica regularly has some pollen, whereas no pollen development has been found in specimens of P. arctica subsp. caespitans in which agamospermy and proliferation seems to be nearly obligate (R. Elven, personal communication, 1999).

Illustrations. • Close-up of plant. Large, caespitose plant. Nunavut, Baffin Island, Arctic Bay. 21 Aug., 1995. L.J. Gillespie 6068. CAN. • Contrasting three species. A. Very bluish plants of Poa glauca. B. Shorter greener plants of P. arctica. C. Lush bluish green plants of Poa pratensis subsp. alpigena growing together in disturbed ground. Baffin Island, Iqaluit. 19 August, 2006. Aiken. No Voucher. • Close-up of plant: Baffin Island, Ogac Lake. Plant beside the marker, growing among rocks close to the edge of the lake. Rocks removed to expose the base of the plant. Nunavut, Baffin Island, Ogac Lake. 13 July, 2004. Aiken and LeBlanc 04–094. CAN 586566. • Close-up of base of plant. Plant with short rhizomes and curving structure to the base of new culms. Nunavut, Baffin Island, Ogac Lake. 13 July, 2004. Aiken and LeBlanc 04–094. CAN 586566. • Arctic Island Distribution.

This publication is available on the internet (posted May 2011) and on CD-ROM (published in 2007). These versions are identical in content, except that the errata page for CD-ROM is accessible on the main index page of the web version.

Recommended citation for the web-based version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. NRC Research Press, National Research Council of Canada, Ottawa. http://nature.ca/aaflora/data, accessed on DATE.

Recommended citation for the CD-ROM version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. [CD-ROM] NRC Research Press, National Research Council of Canada, Ottawa.