Flora of the Canadian Arctic Archipelago
English: Alpine brook saxifrage,
French: Saxifrage des ruisseaux.
Saxifragaceae, Saxifrage family.
Published in Sp. Pl. 404. 1752.
Type: Northern Sweden. Linnaeus (1737), Flora Lapponica; t. 2, f. 7, selected by Jonsell and Jarvis, Nord. J. Bot. 22: 73 (2002). Lectotype. See reasons for rejection of the lectotype (Stockholm Linnaean Herbarium (S) 174.5) selected by Webb, Bot. J. Linn. Soc. 95: 264 (1987).
Vegetative morphology. Plants 2–12 cm high; perennial herbs (dwarf delicate plants); not caespitose (loosely tufted); sometimes vegetatively proliferating by bulbils on stems or leaves (consisting of a few thick scale leaves at the base of the plant), or never vegetatively proliferating by bulbils on stems or leaves, in inflorescences, from gemmiphores and gemmae, or by fragmentation. Ground level or underground stems horizontal, or absent (on some herbarium specimens); stoloniferous (as horizontally growing "runners", to 6 cm long, with glandular hairs on the surface, and with scale leaves. The runners bend upwards, producing roots and foliage leaves), or rhizomatous (as an abbreviated, vertical rhizome, sometimes not readily visible); elongate, or compact. Caudex absent. Aerial stems erect; not filiform. Leaves present; not heterophyllous; mainly basal; erect (or spreading slightly); alternate; dying annually and non-persistent. Petioles (15–)20–40(–50) mm long; glabrous, or hairy (especially on the margins at the flared base); pilose (if applicable). Petiole hairs shorter than the diameter of the petiole. Leaf blades simple. Leaf blade bases cuneate (usually), or truncate. Blades 2–10 mm long, 3–14 mm wide (leaves on average larger than those in S. hyperborea), triangular (obtriangular), flat, veins palmate or with inconspicuous veins. Blade adaxial surface glabrous. Blade abaxial surface glabrous. Blades lobed (with (3-)5(-7)). Blade margins entire, glabrous; degree of incision 50–70%. Hydathodes present and conspicuous, or present but inconspicuous (at the apex of each leaf lobe, but easily overlooked). Blade apices acute.
Reproductive morphology. Flowering stems two or more per plant; about as high as the leaves; with leaves (often conspicuously large, with margins lobed, near the flowers). Flowering stems hairy. Flowering stems woolly (near the flowers). Flowering stem hairs branched; longer than the diameter of the flowering stem; white or translucent (with dark glands); glandular hairs present. Flowers solitary, or in inflorescences. Inflorescences paniculate (if applicable). Pedicels present; with glandular hairs. Flowers per inflorescence 1–2; small, or medium-sized; radially symmetrical (actinomorphic). Sepals conventional; 5; free; 1.2–2.2 mm long; 2.5–3.5(–4) mm wide; green. Calyx glabrous (hypanthium hairy). Petals conventional; free; longer than the calyx; 5; white and purple (as a tinge of colour at the base of each petal); obovate, or elliptic (narrow); unlobed; (3.5–)4.5–5.5 mm long; 1–2 mm wide. Stamens 10; stamen filaments glabrous; free of the corolla. Anthers yellow; sub-globose; (0.2–)0.3–0.5 mm long. Nectaries present. Receptacle (1.5–)2.5–3.5 mm high. Ovary partly inferior; carpels 2; partly fused. Ovaries glabrous. Placentation axile. Ovules per ovary 50–100. Fruit with calyx persisting; dry; a capsule; urceolate; brown, or straw-coloured; 5–7.5 mm long; 2–4 mm wide; glabrous; surface venation ribbed; dehiscent; splitting to the base into separate segments. Seeds 50–100; 0.5–0.6 mm long; brown; surfaces smooth.
Chromosome information. 2n = 50, or 52, or 56.
(2n) (4x) = 50-52-56. Böcher (1938a, Greenland? 2n = 56); Sørensen and Westergaard, in Löve and Löve (1948, Greenland); Löve and Löve (1951, 1956, Iceland; 1965, North America; 1982a, Arctic Canada); Jørgensen et al. (1958, Greenland);
2n = 50–52, 51–53, 52. Engelskjøn and Knaben (1971, northern and arctic Norway);
2n = 50–52. Engelskjøn (1979, southern Norway and Bear Island, 2n = 52, 3 counts); Borgen and Elven (1983, northern Norway).
The following tetraploid chromosome counts from the amphi-Beringian area have been preliminarily excluded; they may belong to S. arctolitoralis or a relative: Zhukova (1968, northeastern Asi), Zhukova and Tikhonova (1971, 2n = 52; 1973, Chukotka, 2n = 48), and Packer and McPherson (1974, northern Alaska, Point Barrow). A count from western North America (Rocky Mountains) may belong to S. rivularis: Löve et al. (1971). These counts, together with those of S. arctolitoralis from the Asian side, might indicate the presence of an arctic amphi-Beringian tetraploid that should be critically compared with both S. rivularis and S. hyperborea.
Ploidy levels recorded 4x.
Ecology and habitat. Substrates: wet meadows, along streams, lakeshores; imperfectly drained moist areas, seepage slopes (gravelly, and mossy places, or wet slopes); sand, clay, moss; with high organic content, peat; nitrophilous, or non-calcareous (found below bird cliffs and near human habitations. Described as "markedly calcifugous", Polunin 1940. Much more often found in circumneutral or acidic sites. This is a difference from S. hyperborea).
North American distribution. Nunavut Islands, continental Nunavut (?), northern Quebec, Labrador. Range in the Canadian Arctic Archipelago limited. Uncommon, rare. Arctic, alpine. Arctic islands: Baffin, Coats.
Northern hemisphere distribution. Amphi-Atlantic. Northern Iceland, Northern Fennoscandian, KaninPechora, Svalbard Franz Joseph Land, Polar Ural Novaya Zemlya, Labrador Hudson Bay, Ellesmere Land Peary Land (?), West Greenland, East Greenland.
General notes. Polunin (1940) indicated that this is one of the most ubiquitous and generally common of arctic plants. At that time he included S. hyperborea in S. rivularis, and almost all his statements refer to the former rather than the latter.
This is an Amphi-Atlantic arctic species that previously included S. hyperborea. "At present, only plants with stolons and 2n = 52 are attributed to S. rivularis. However, the [distinctiveness of the growth forms] and other morphological distinctions between S. rivularis and S. hyperborea are not always obvious" (Zhmylev in Elven et al. 2003), and the problem was studied by Jørgensen (2004).
Jørgensen (2004), in a thesis done at Oslo (with Elven, R., Stedje, B., Gabrielsen, T.M., and Brochmann, C.), studied reticulate evolution and species delimitation in the arctic Saxifraga rivularis complex and found there is a very good correspondence between molecular genetic evidence, chromosome ploidy evidence, and morphological evidence for the structure they proposed in the Saxifraga rivularis group.
The amphi-Atlantic Saxifraga rivularis L. subsp. rivularis and the now amphi-Beringian S. rivularis subsp. arctolitoralis (Jurtzev & Petrovsky) M.H.Jørg. & Elven are allotetraploids, and they have a common parentage from one or more crossed between S. bracteata and S. hyperborea. The origin is therefore suspected to be Beringian. However, there is a vast gap between the ranges of these two subspecies, also associated with some small morphological differences and some slight molecular differences. It is therefore appropriate to recognise them as two subspecies, but not as two species.
A survey of the Alaska and Yukon material (in ALA) proved S. rivularis subsp. arctolitoralis to be fairly common in NW and N Alaska. It reaches close to the Canadian border but has not yet been found in Canada.
Illustrations. • Habitat: Cape Dorset. Bluish green clumps of Saxifraga rivularis with white flowers in foreground and at left (Aiken 05–095) growing with reddish more erect plants of Saxifraga hyperborea in centre (Aiken 05–096). Baffin Island, Cape Dorset. 5 August, 2005. Aiken. CAN. 586964. • Habitat: Pond Inlet. Loosely clustered plant growing in moist moss under the staircase of the Renewable Resources Building. Nunavut, Baffin Island, Pond Inlet. L.J. Gillespie 6042. CAN. • Habit. Close-up of plant showing leaves having deeply lobed blades that taper into the petioles, and flowers with five free petals and yellow anthers. Nunavut, Baffin Island, Pond Inlet. L. Gillespie 6042. CAN. • Pressed plant with rhizome. Note the presence of a rhizome (a). This helps to distinguish this taxon from S. hyperborea that never has rhizomes. Nunavut, Baffin Island. 16 August, 1995. L.J. Gillespie 6042. CAN 582573. • Pressed plant showing position of inflorescence. Note the inflorescence (a) borne on a flowering stem with leaves e.g. (b) high up near the inflorescence. Nunavut, Baffin Island. 16 August, 1995. L.J. Gillespie 6042. CAN 582573. • Surface view of plant: Baffin Island. Dark developing fruit surrounded by three green sepals. Plant growing in shallow standing water. Nunavut, Baffin Island, Sylvia Grinnell Park. 1 August, 2005. Aiken and A. Archambault 05–073. CAN 586945. Photograph by Kathy Thornhill. • Leaf shape. Leaves vary in shape from unlobed to 3-(arrow) or 5-lobed. They appear glabrous at a distance, but close-up are seen to have a few glandular hairs. L.J. Gillespie 6042. CAN. • Close-up of flowers. The flowers have five white petals with a tinge of pink towards the base, 10 stamens, and two green carpels topped with white stigmas. Nunavut, Baffin Island, Pond Inlet. L.J. Gillespie 6042. CAN. • 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..