Flora of the Canadian Arctic Archipelago

DELTA
Home

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

Acomastylis rossii (R. Br.) Greene

Rosaceae, Rose family.

Published in Leafl. Bot. Observ. 1: 174. 1906.

Synonymy. Sieversia rossii R. Br., Chlor. Melvil. 18. 1823.

Geum rossii (R. Br.) Ser., in DC., Prodr. 2: 553. 1825.

Vegetative morphology. Plants 20–40 cm high; perennial herbs; caespitose. Taproot present. Ground level or underground stems horizontal, or vertical (orientation of the stem appears to vary with substrate); rhizomatous; elongate; 2–20 mm wide. Caudex present (bases very stout, sub-ligneous, covered with the marcescent remains of old leaves). Aerial stems rhizome from which leaves arise; erect, or ascending. Leaves mainly basal, or basal in a rosette; alternate; dying annually and non-persistent and marcescent (leaf blades deciduous; petioles and stipules marcescent). Stipules present; (7–)8–12 mm long; 2.5–3.5 mm wide; brown, or pink or reddish; glabrous; apex acute (fused to the base of the petiole). Petioles 20–35 mm long (to 50 cm tall further south); glabrous. Leaf blades compound. Blades 20–30(–40) mm long, 8–15(–20) mm wide, veins palmate (leaflet veins pinnate). Blade adaxial surface glabrous (on blade surfaces) or hairy (on the margins). Blade abaxial surface dull, glabrous (on blade surfaces) or hairy (on the margins), hairs white (if applicable), hairs spreading. Blade margins serrate or entire (smaller blade divisions), with non-glandular hairs, with 2 teeth on each side of the blade or 1 teeth on each side of the blade (on small arctic plants), with teeth toward the apex; degree of incision 70–80% (major incisions, minor incisions commonly 10–50%); apices acute, or obtuse. Leaflet arrangement pinnate. Leaflets 12–16; 7–15 mm long; 2–4(–5) mm wide; oblong; veins conspicuous. Apical leaflet base not distinctly stipitate.

Reproductive morphology. Flowering stems conspicuously taller than the leaves; with leaves. Flowering stems hairy. Flowering stems woolly. Flowering stem hairs simple; shorter than the diameter of the flowering stem, or longer than the diameter of the flowering stem; white or translucent; glandular hairs present. Flowers solitary (usually in the Arctic), or in inflorescences (with 2–3 flowers, further south). Inflorescences cymose; diffuse (if applicable); elongating as the fruit matures. Pedicels absent (usually), or present (if in inflorescences). Flowers per inflorescence 1 (usually), or 2–3; medium-sized (Arctic), or large (warmer habitats). Sepals conventional. Epicalyx present. Epicalyx segments 4–5 mm long. Epicalyx segments 1–2 mm wide. Epicalyx segments equal in length to the calyx segments (approximately). Epicalyx segments narrower than the calyx segments. Sepals 7–10; free; 1.5–3 mm long; 4.5–7 mm wide; green. Calyx hairy. Calyx hairs long-silky; white or translucent. Petals conventional; free; 5–7; yellow; obovate (to almost circular); unlobed; (5–)8–10(–15) mm long; 7–10 mm wide. Stamens 30–50(–60); stamen filaments glabrous. Anthers yellow; sub-globose; 0.4–0.6 mm long. Ovary superior; carpels 10–30(–50); apocarpous. Styles 2–6 mm long; conical; basal portion with hairs at the base. Ovules per ovary 1. Fruit with calyx persisting; dry; an aggregate of achenes; ovoid; black, or brown, or red, or green at maturity, or golden brown, or straw-coloured; 3–4 mm long; 7–9 mm wide (individual achenes 2–2.5 mm long, excluding the style; 0.4–0.6 mm wide, covered in upward pointing hairs); glabrous, or hairy; surface venation reticulate, or appearing veinless; indehiscent. Styles modified and persisting, or persisting but not modified; becoming hooked.

Chromosome information. 2n = 56 (1 count), or 70 (2 counts).

2n (8x) = 56. Gajewski (1957); Wiens and Halleck (1962, western North America); Mosquin and Hayley (1966, northern Canada);

2n = about 56. Zhukova (1967a, 1969, northeastern Asia); Zhukova and Petrovsky (1976, 1987b, northeastern Asia);

2n (10x) = 70. Zhukova (1966, 1967a, 1969, northeastern Asia); Mulligan and Porsild (1969b); Löve et al. (1971, western North America); Zhukova and Tikhonova (1971, 1973, Chukotka); Zhukova et al. (1973, northeastern Asia); Dawe and Murray, in Löve (1979, Alaska); Zhukova and Petrovsky (1980, 1987b, northeastern Asia).

Ploidy levels recorded 8x and 10x.

Ecology and habitat. Substrates: wet meadows (occasionally, e.g., CAN 268168, 320126), tundra, slopes (gentle or flat); imperfectly drained moist areas, seepage slopes, solifluction slopes, dry (rarely, e.g., CAN 342945); rocks, clay; with low organic content; calcareous.

North American distribution. Alaska, Yukon, Nunavut Islands. Range in the Canadian Arctic Archipelago limited. Uncommon. High Arctic. Arctic islands: Ellesmere, Axel Heiberg, Parry islands (Bathurst, Emerald, and Melville).

Northern hemisphere distribution. Amphi-Beringian, or Cordilleran. West Chukotka, South Chukotka, East Chukotka, West Alaska, North Alaska – Yukon, Central Canada, Ellesmere Land – Peary Land, East Greenland.

General notes. Hebda and Chinnappa (1990) reported that the pollen of this taxon is produced in monads that are isopolar, radially symmetrical, and tetracolporate, and they described the pollen in detail.

Chambers et al. (1990) observed the effects of disturbance type on seedling environment and establishment of alpine species with different physiological and life history traits during a 2-year study on the Beartooth Plateau in southwestern Montana, USA. They compared soil temperatures, water potentials, and nutrients on mineral soils of a gravel borrow area with those on highly organic soils of a Acomastylis (Geum) turf area. They concluded that successful seedling establishment on different alpine disturbance types may depend more on obtaining the necessary conditions for seedling emergence and on species interactions than on the ability of seedlings to survive different environmental conditions.

Chambers (1991) studied the relationships of clone area and neighbourhood to ramet size, reproductive effort, and spatial distribution within A. rossii clones in an alpine ecosystem on the Beartooth Plateau, Montana, USA. Conservative patterns of growth and reproduction make A. rossii well suited to dominate in dense, heterogeneous neighbourhoods of late seral sites and to colonise mineral soils of early seral sites. Similar to other clonal species, site characteristics and the type of neighbourhood determine the trade-off between the physical occupation of space and the allocation to ramet growth and reproduction in A. rossii.

Illustrations. • Close-up of plant. Plant in flowering stage. Alaska, Seward Peninsula, Distin Mountain. July, 1998. Voucher at 0. Photograph by R. Elven. • Close-up of leaf and flower from side. Leaf showing the irregular pinnae. Side view of flower showing episepals and sepals. Alaska, Seward Peninsula, Kigluaik Mountains, Anfield Creek. August, 2001. Voucher at 0. Photograph by Heidi Solstad. • Close-up of flower. Flower showing stamens and carpels. Alaska, Seward Peninsula, Kigluaik Mountains, Anfield Creek. August, 2001. Voucher at 0. Photograph by Heidi Solstad. • Close-up of plant. Plants with shiny, glabrous, pinnately compound leaves and flowers with yellow petals. Alaska, Lake Peters. 13 July, 1961. CMN Photo library S78–634. Photograph by Raymond Wood. • 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.

.

Contents