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

Saxifraga cernua L.

English: Nodding saxifrage, bulblet saxifrage,

French: Saxifrage penchée,

Inuktitut: Nunaraq qupanuap niqinga.

Saxifragaceae, Saxifrage family.

Published in Sp. Pl. 403. 1753.

Type: Selected by Webb, Bot. J. Linn. Soc. 95: 264 1987. Lectotype: LINN 575.44.

Synonymy. Saxifraga cernua f. ramosa Gmel., Flor. Sibir. 6: 162. 1769.

Saxifraga cernua f. bulbillosa Engler and Irmsch., In Engler. Das Pflanzenreich 86. 274. 1916.

Saxifraga cernua f. latibracteata (Fernald and Weatherby) Polunin, J. Bot. 76: 100. 1938.

Saxifraga cernua var. exilioides Polunin, Bull. Natl. Mus. Canada 94 (Biol. Ser. 24): 254. 1940.

Vegetative morphology. Plants 10–25(–35) cm high; perennial herbs; sometimes vegetatively proliferating by bulbils on stems or leaves (white bulbils at the base of the plants; dark red in leaf axils on the flowering stems; in the Arctic, proliferation is always by these methods - seeds have never been observed). Ground level or underground stems horizontal (in older plants). Caudex present (small). Aerial stems erect. Leaves present; heterophyllous (upper flowering stem leaves reduced, often bract-like, linear and not lobed, 1.5–7 mm long, 0.3–3.0 mm wide, sessile); mainly basal and distributed along the stems; erect (or spreading); alternate; dying annually and non-persistent. Petioles 10–50 mm long; hairy; villous. Petiole hairs longer than the diameter of the petiole. Leaf blades simple. Leaf blade bases cordate, or rounded (basal leaves), or truncate (flowering stem leaves). Blades (3–)5–15(–20) mm long, 5–25(–35) mm wide, obovate (sometimes) or reniform, flat, veins palmate or with inconspicuous veins. Blade adaxial surface glabrous or hairy, hairs puberulent (if applicable), hairs simple, hairs sparse, hairs white, or translucent. Blade abaxial surface glabrous or hairy, hairs puberulent, hairs sparse, hairs white (if applicable). Blades lobed (5–7, rarely 3–9, rounded to acute lobes). Blade margins entire and crenate (deeply so; leaf margins variable in outline), glabrous or with non-glandular hairs (sparse); apices rounded.

Reproductive morphology. Flowering stems with leaves (gradually reduced in size towards the inflorescence). Flowering stems hairy. Flowering stems villous. Flowering stem hairs simple; shorter than the diameter of the flowering stem, or longer than the diameter of the flowering stem; white or translucent (usually); glandular hairs present. Flowers solitary (sometimes absent), or in inflorescences. Inflorescences with bulbils (in axils of reduced leaves below the flowers); cymose (if applicable); 0–2.5 cm long. Pedicels present, or absent. Flowers per inflorescence 0–1 (usually, sometimes 2(-5)); medium-sized. Sepals conventional; 5; free; 1.4–1.6 mm long; 3–4 mm wide; green. Calyx hairy. Calyx hairs glandular. Petals conventional; free; 5; white; obovate, or spatulate; unlobed; 5–12 mm long; (2.5–)3–4 mm wide. Stamens 10. Anthers yellow; sub-globose; 0.5–0.6 mm long. Nectaries present. Receptacle 1–2 mm high. Ovary superior; carpels 2; partly fused. Ovaries glabrous. Placentation axile. Fruit with calyx persisting; dry; a capsule (not yet found fully developed in CAN specimens from the Arctic islands or further south); brown; hairy; dehiscent; splitting to the base into separate segments.

Chromosome information. 2n = 24–72.

(2n) = 24–72.

Zhukova and Petrovsky (1987a, northern Asia), 2n = 24, 26, 48, 48–50, 52, 56, about 60, 72;

2n = 24. Zhukova (1980, southern Chukotka);

2n = 36. Sokolovskaya (1982);

2n = 36, about 60 Sokolovskaya and Strelkova (1960);

2n = 44–46. Engelskjøn (1979, southern Norway);

2n = 48, 56. Zhukova (1982, northeastern Asia);

2n = 48–50, 56, 60, 70. Zhukova (1968, 1969, northeastern Asia);

2n = about 50. Johnson and Packer (1968, northwestern Alaska); Sokolovskaya 1970);

2n = 52. Löve and Löve (1982a, Arctic Canada); Zhukova and Petrovsky (1972, 1976, western Chukotka); Zhukova and Tikhonova (1971, Chukota);

2n = about 54, 72. Mosquin and Hayley (1966, northern Canada);

2n = 55–57. Knaben and Engelskjøn (1967, southern Norway);

2n = 56. Zhukova and Petrovsky (1971, Wrangel Island);

2n = about 60. Sokolovskaya (1958);

2n = about 66. Skovsted (1934, southern Norway); Sørensen and Westergaard, in Löve and Löve (1948, Greenland);

2n = 60–70. Jørgensen et al. (1958, Greenland);

2n = 62. Zhukova et al. (1973, northern Siberia and northeastern Asia);

2n = about 64. Löve and Löve (1951, 1956, Iceland);

2n = about 68. Packer and McPherson (1974, northern Alaska);

2n = about 70. Hedberg (1967, northern Canada);

2n = 70. Mulligan and Porsild (1969, Yukon).

Taxon as an environmental indicator. This is a morphologically very plastic taxon in which the habit of the plant and size of the leaves may indicate favourable or unfavourable environmental conditions. The northernmost record is Low Point, 83°06'N, on the north coast of Greenland. It has been collected in Canada from Ward Hunt Island, 83°05'N (Canada).

This is a circumpolar arctic-alpine species propagating mainly vegetatively (by pseudovivipary). Probably it is a complex of two close species and formed as a result of polyploidy in pseudoviviparous races of S. radiata and S. sibirica (Zhmylev, personal communication, 2003).

Ecology and habitat. Substrates: snow patches; imperfectly drained moist areas (near creeks and lakeshores, on moist ledges and in exposed dry sites); acidic, or calcareous, or nitrophilous (often near Thule sites and human habitation), or circum-neutral. Polunin (1940) noted that in the Canadian Arctic Archipelago, this species frequently flowers far into the summer, but has not been observed to set seed. It reproduces by means of numerous reddish bulbils produced in the axils of the flowering stem leaves and bracts. No seeds were found in a thorough search of all specimens at CAN in 1996. Seed-set has been observed several times, in other parts of the world Gabrielsen and Brochmann (1998).

North American distribution. Alaska, Yukon, Northwest Territories Islands, continental Northwest Territories, Nunavut Islands, continental Nunavut, northern Quebec, Labrador. Range in the Canadian Arctic Archipelago widespread. Common. Arctic, alpine. Arctic islands: Baffin (Bylot, Digges, Lower Savage, Mills, Prince Charles, Resolution, Salisbury), Devon, Ellesmere, Axel Heiberg, Parry islands (Bathurst, Cameron, Eglingon, Emerald, Helena, Melville, Prince Patrick), Cornwallis, Banks, Victoria, Prince of Wales, Somerset, King William, Southampton, Coats (Meighen, Loughead, Ellef Ringnes, Amund Ringes, Nothingham, Mackenzie islands, Boothia and Melville peninsulas).

Northern hemisphere distribution. Circumpolar, or circumboreal (arctic-alpine). 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. Elven et al. (2003) noted that the S. cernua aggregate consists of a series of taxa from diploid to high-polyploid levels, accompanied by a transfer from sexual seed propagation to propagation by bulbils (and runners). The three arctic taxa are fairly different but related. Their relationships to the probably mainly diploid, sexual, and more southern S. sibirica L. is also fairly clear that it is a circumpolar arctic-alpine species propagating mainly vegetatively (by pseudovivipary) and probably it is a complex of two close species, formed as a result of polyploidisation in the pseudoviviparous races of S. radiata and S. sibirica. Seed reproduction does occur in S. cernua, although fairly rarely and as a small proportion of the total reproduction.

Porsild (1957) described this species as "nodding in youth". Field observations are that the nodding may occur before and after anthesis.

Polunin (1940) recognised taxa that we have not recognised as distinct. These were as follows:

1. subsp. cernua, the usual one occurring throughout the Canadian Arctic Archipelago.

2. var. exiliodes Polunin. Plants occurring on the mainland regions of the Northwest Territories.

3. forma latibracteata (Fernald and Weath.) Polunin. This taxon had been recognised as a variety, but Polunin noted that while it initially appeared to have the geographical delimitation of a true variety, it has since been found to be a merely frondose phase developed almost everywhere that the species grows in humid places among rocks in the Canadian Arctic Archipelago. It had been distinguished on the characters: leaf blades larger, 10–55(-70) mm long, 8–20(-25) mm wide; 5–8 lobed.

4. forma bulbillosa Engler and Irmsch. "bulbillis nigris permultis dense instructis". Polunin (1940) described this as a forma crassa, which in our area has been collected on the west coast of Hudson Bay (in the case of Macoun's Fullerton material "on wet refuse from dog stalls") and on the closely adjacent Southampton Island. It forms a marked contrast to the slender and graceful var. exilioides of the same region.

5. forma ramosa. A rare form that Polunin (1940) considered to have been collected in the Arctic Archipelago.

Porsild (1957) and Hultén (1968), Porsild and Cody (1980) did not recognise any of the intraspecific taxa in the above list. Saxifraga cernua is one of the chief plants in the High Arctic. It has a very wide range of tolerance to most environmental conditions, occurring in almost all habitats from wet to very dry and sheltered to exposed, and doing especially well in manured areas and snow patches. It is highly resistant to frost. This taxon appears to be a phenotypically plastic one in which various expressions have been named.

Saxifraga cernua was one of seven arctic species studied at Truelove Inlet, Devon Island (Atkin et al. 1993), for their ability to utilise nitrate nitrogen under field conditions. Saxifraga cernua, S. oppositifolia, Cerastium alpinum, Oxyria digyna, and Papaver radicatum s.l. were able to use nitrate nitrogen, while Dryas integrifolia and Salix arctica showed little utilisation. Porsild (1957, 1964) and Porsild and Cody (1980) recognised a single taxon for this species and did not accept any of the four intraspecific taxa recognised by Polunin (1940). No reason to do so has been found.

Molau (1992) discussed the occurrence of sexual reproduction in this species.

Kjølner et al. (2004) studied the clonal diversity in S. cernua using amplified fragment length polymorphisn and random amplified polymorphic DNA markers.

Illustrations. • Habitat with willows: Cape Dorset. Plants common among Salix arctica on the side of a hill. Nunavut, Baffin Island, Cape Dorset. 2 August, 2005. Aiken. No Voucher. • Habitat with fireweed. Plant beside the marker growing on relatively bare ground. Nunavut, Baffin Island, Cape Dorset. 2 August, 2005. Aiken. No voucher. Scale bar in cm. • Rocky habitat: Dorset. Flowering plant with branching flowering stems growing among rocks near shoreline. Stellaria longipes in the background. Nunavut, Baffin Island, Cape Dorset. 2 August, 2005. Aiken. No voucher. Scale bar in cm. • Habitat: Cornwallis Island. Plants growing in moist gravel with single terminal white flowers and numerous red bulbils up the flowering stems. Bulbils detach and may develop into new plants. L.J. Gillespie s.n. • Close-up of plants: Southampton. Plants 30–50 cm tall between the markers. Aiken and Brysting 01–033. CAN. Scale bar in cm. • Habitat in moss. Plants growing in a thick cover of moss. Terminal flowers, usually with 5 white petals, are borne erect. CMN Photo-Library. • Close-up of plants. Plants with a single, erect, terminal flower growing in wet calcareous gravel and moss. Nunavut, Cornwallis Island, Resolute Bay, west side of Satellite Hill Road, 7440'N, 9450'W. Aiken 98–056. CAN. Scale bar in cm. Photograph by Mollie MacCormac. • Line drawing of plant. Base of plants showing fibrous roots, short bulb leaves, leaves with long petioles, and the deeply crenate leaf blades. Warming 1909. p. 179. • Inflorescence and bulblets. Flowering stem with a single terminal flower and red bulbils (arrow). CMN Photo-Library. Photograph by D. R. Gunn. • Close-up of flower. Terminal solitary flower, with 5 white petals, 10 anthers and two carpels topped with white pom-pom stigmas. Flowering stem with red vegetative bulbils. Nunavut, Cornwallis Island. Aiken 98–056. CAN. Scale bar in cm. Photograph by Mollie MacCormac. • Close-up of flower. Flower with 5 to 6 white-notched petals showing variation in shape, and 10 anthers (not all of which are visible). There are two carpels topped with stigmas. CMN Photo Library. • 'Nodding' inflorescence. Flowering stem 'nodding' from the weight of a developing fruit. This is the origin of its common name 'Nodding Saxifrage'. Note there are 3-and 5-lobed leaves on the same plant. Nunavut, Cornwallis Island, Resolute Bay. Photograph by Mollie MacCormac. • 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.