Flora of the Canadian Arctic Archipelago

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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

Micranthes tenuis (Wahlenb.) Small

English: Alpine saxifrage, Ottertail Pass saxifrage, Slender saxifrage.

Saxifragaceae, Saxifrage family.

Published in N. Amer. Fl. 22, 2: 136. 1905.

Type: Sweden: "Saxifraga nivalis b., Luleå fjällen på södra sidan af Kajsats", 30.07.1807, leg. Wahlenberg, selected by Moberg and Nilsson, Nordic J. Bot. 11: 294. 1991. Lectotype: UPS.

Synonymy. Saxifraga nivalis L. var. (beta) tenuis Wahlenb., Fl. Lapp. 114. 1812.

Saxifraga tenuis (Wahlenb.) Harry Sm. ex Lindm., Sv. Fanerogamfl. 300. 1918.

Vegetative morphology. Plants (2–)3–7(–9) cm high; perennial herbs; caespitose. Roots black. Ground level or underground stems absent. Caudex present (SMALL). Aerial stems erect. Leaves not heterophyllous; basal in a rosette; patent; alternate; persistent. Petioles present; 0.5–2.5(–3) mm long; hairy; pilose, or villous. Leaf blades simple. Leaf blade bases obtuse, or attenuate (broadly). Blades 4–20 mm long (mean 7 mm), 2–18 mm wide (mean 5 mm), ovate or obovate or spatulate, flat, appearing single-veined or with inconspicuous veins. Blade adaxial surface glabrous. Blade abaxial surface hairy, hairs pilose or villous, hairs sparse or moderately dense, hairs a mixture of white and rust-coloured. Blade margins serrate, glabrous (often) or with glandular hairs (on the lower half), with 3–6 teeth on each side of the blade, with teeth toward the apex; apices obtuse, or rounded, or acute (rarely).

Reproductive morphology. Flowering stems without leaves, or with leaves (close to the inflorescence); pilose, or villous. Flowering stem hairs simple; transparent with deep purple cross-walls (usually), or white or translucent (occasionally); glandular hairs present. Inflorescences racemose (pedicels longer, inflorescence open, and with fewer flowers than S. nivalis). Pedicels present. Flowers small, or medium-sized. Sepals conventional; 5; free; green, or purple. Calyx glabrous. Petals conventional; free; longer than the calyx, or same length as the calyx; 5; white, or pink; without contrasting markings (but tips of the petals reddish); ovate, or elliptic (tip often rounded); unlobed; 1.2–2.5 mm long (mean 1.7 mm); 0.5–1.2 mm wide (mean 0.7 mm). Stamens 10. Ovary partly inferior; carpels 2; partly fused. Placentation axile. Ovules per ovary 50–100 (approx.). Fruit with calyx persisting; dry; a capsule; spherical (in the lower half, free portion of the carpels reflexed); brown, or purple; 3–4 mm long; 3–4.5(–5) mm wide; glabrous; dehiscent; splitting to the base into separate segments. Seeds 50–100 (approx.); 0.5–1 mm long; brown (yellowish); surfaces verrucose.

Chromosome information. 2n = 20.

(2n) (2x) = 20. Arwidsson (1938, northern Europe); Böcher (1938a); Flovik (1940, Svalbard); Löve and Löve (1944b, northern Europe; 1951, Iceland; 1956, Iceland); Sørensen and Westergaard, in Löve and Löve (1948, Greenland); Holmen (1952, Greenland); Löve (1954b, northern Europe); Jørgensen et al. (1958, Greenland); Sokolovskaya (1958); Sokolovskaya and Strelkova (1960); Hedberg (1967, northern Canada, 2n = about 20); Knaben and Engelskjøn (1967, southern and northern Norway); Zhukova (1968, northeastern Asia; 1980, southern Chukotka; 1982, northeastern Asia); Zhukova et al. (1973, Chukotka); Krogulevich (1976a, northern Siberia); Engelskjøn (1979, northern Norway and Bear Island); Yurtsev and Zhukova (1982, northern Siberia); Zhukova and Petrovsky (1987b, northeastern Asia); Dalgaard (1989, western Greenland); Devyatov et al. (1997, northern Siberia and northeastern Asia).

Ploidy levels recorded 2x.

Ecology and habitat. Substrates: wet meadows, snow patches, around the margins of ponds, marshes, along streams; imperfectly drained moist areas, seepage slopes, moderately well-drained areas (in closed marshes and on open patches of damp soil, on solifluction slopes and in places where the surface may become dry in late summer, rarely found in dry areas (Elven, personal communication)); rocks, gravel, sand, silt, clay, till, moss; acidic, or nitrophilous, or calcareous.

North American distribution. Alaska, Yukon, Northwest Territories Islands, Nunavut Islands, northern Quebec, Labrador. Range in the Canadian Arctic Archipelago widespread. Common (less frequent than S. nivalis). Arctic. Arctic islands: Baffin, Devon, Ellesmere, Axel Heiberg, Parry islands, Cornwallis, Banks, Victoria, Prince of Wales, Somerset, and King William.

Northern hemisphere distribution. Circumpolar. Northern Iceland, Northern Fennoscandian (?), Kanin–Pechora, Svalbard – Franz Joseph Land, Polar Ural – Novaya Zemlya, Yamal–Gydan, Taimyr – Severnaya Zemlya, Anabar–Olenyok, Kharaulakh, Yana–Kolyma, West Chukotka, Wrangel Island, South Chukotka, East Chukotka, West Alaska, North Alaska – Yukon, Central Canada, Labrador – Hudson Bay, Ellesmere Land – Peary Land, West Greenland, East Greenland.

General notes. Micranthes tenuis has been treated either as a distinct species or as a variety of M. nivalis, and both were previously treated within the genus Saxifraga. Polunin (1940) commented that the two taxa are difficult to separate and suggested the need for breeding and cytological studies before distinguishing them at the species level. Subsequently, Porsild (1957) and Porsild and Cody (1980) recognised S. tenuis as a distinct species in the Canadian Arctic, as it was in Europe (Webb 1964, 1993) and Greenland (Böcher et al. 1968, 1978). More recently Scoggan (1978) and Aiken et al. (1998) treated the two taxa as varieties of S. nivalis.

Healy and Gillespie (2005) investigated the systematics of the S. nivalis (= M. nivalis) species complex in the Canadian Arctic islands using morphology and chloroplast DNA restriction site data (see also under M. nivalis). Their results supported the recognition of two closely related, largely sympatric species, S. nivalis and S. tenuis. The two species can be distinguishable based on both molecular and cytological characters and have morphological characters that correspond to these differences. While no morphological characters gave 100% separation, numerous characters, both quantitative and qualitative, showed statistically significant differences. However, both species showed considerable morphological variability, and the presence of intermediate specimens suggests they may hybridise. Micranthes tenuis is most common in the High Arctic and eastern Canadian Arctic islands; its range is included within that of the more widespread and common M. nivalis. Although their habitat preferences differ (M. tenuis preferring wetter sites), there is considerable overlap, with the two taxa sometimes occurring in mixed populations.

Micranthes tenuis may be distinguished from M. nivalis by its typically more delicate habit, narrower sparsely hairy flowering stems with short fine hairs, open cyme with fewer flowers on distinct pedicels, and usually pink petals.

Illustrations. • Habitat: Dorset. Plants with reddish flowers growing beside the marker. Very lush growth in narrow runoff below where dogs have been tied up. Nunavut, Baffin Island, Cape Dorset. 5 August, 2005. Aiken 05–090. CAN. 586960. • Close-up of lush plants. Plants nearly 20 cm high with vivid purpish flowering heads setting seed. Nunavut, Baffin Island, Cape Dorset. 5 August, 2005. Aiken 05–090. CAN 586960. • Close-up of plant. Branching scape and back lit hairs that are much shorter than those of M. nivalis. Image L1050, R. Elven. • Close-up of plant. Plant with branching inflorescence and terminal flower in fruit with strongly recurved tops to the carpels. N.W.T., Melville Island, McCormick Inlet. Gillespie 6978 –2 and Consaul. CAN. • Close-up of inflorescence. Plant with branching inflorescence and terminal flower in fruit with strongly recurved tops to the carpels. Note short hairs on the flowering stem. N.W.T., Melville Island, McCormick Inlet. Gillespie 6978 –2 and Consaul. CAN. • Plant with branching inflorescences. Note scapes that branch into head-like clusters of flowers. Nunavut, Baffin Island, Ogac Lake. Aiken and LeBlanc. 04–218. CAN 586600. • Hairs on the scape of the previous image. Note the scape is distinctly branching. Hairs on the scape did not scan well possibly because they are much shorter than those in M. nivalis. CAN 586600. • Close-up of hairs. Hairs lower down the scape of the previous image. These hairs are much shorter than those of M. nivalis. CAN 586600. • 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.

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