Potentilla anserina |
Potentilla tikhomirovii |
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common silverweed, Pacific cinquefoil, silver weed cinquefoil, silverweed |
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Habit | Plants ± tufted. | |||||||||||||
Caudex branches | slender to stout, not columnar, not sheathed with marcescent whole leaves. |
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Stems | ± ascending, sometimes nearly erect, 0.5–1.5(–3) dm, lengths 2–4 times basal leaves. |
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Basal leaves | petiole (0.5–)1–15(–25) cm, long hairs absent or sparse to dense, 1.5–3.5 mm; larger leaflets (0.4–)0.5–5(–7) × (0.2–)0.3–2(–3) cm, surfaces: abaxial with long hairs absent or sparse to abundant, not restricted to veins, 0.5–2(–2.5) mm, cottony-crisped hairs usually dense or usually absent (in subsp. groenlandica), adaxial with long hairs absent or sparse to abundant, cottony-crisped hairs usually absent, sometimes sparse to common (especially subsp. yukonensis). |
2–4 cm; petiole 1–2.5 cm, long hairs common to abundant, spreading to ascending, rarely loosely appressed, 1–2 mm, ± stiff, verrucose, short-crisped hairs sparse to abundant, sometimes nearly absent, cottony hairs absent, glands sparse; leaflets ± overlapping, central elliptic to obovate, 1–1.5 × 0.6–1.1 cm, petiolulate, base broadly cuneate, margins flat or slightly revolute, distal ± 2/3 incised ± 1/2 to midvein, teeth (3–)4 per side, ± approximate, surfaces ± dissimilar, abaxial reddish or greenish gray to white, long hairs 1 mm, cottony-crisped hairs common to dense, adaxial green or reddish to gray-green, long hairs sparse to abundant, short-crisped hairs absent or sparse to common. |
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Cauline leaves | 0–1. |
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Inflorescences | 2–5-flowered. |
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Pedicels | 1–2 cm in flower, to 3(–5) cm in fruit. |
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Flowers | epicalyx bractlets narrowly to broadly ovate-triangular or linear to elliptic, (2–)2.5–7(–8) × (0.3–)0.5–3(–3.5) mm, often 2-fid or dentate; sepals (3–)3.5–7(–9) mm, apex subacute to acuminate; petals (4–)5–15(–20) × (2.5–)3–10(–12) mm; filaments (1–)2.5–3.5(–4.5) mm, anthers 0.7–1.3 mm; carpels (10–)20–200(–250). |
epicalyx bractlets narrowly elliptic to narrowly ovate, 4–6 × 1–2.5 mm, (1/2–)2/3 to as wide as sepals, margins revolute, sometimes flat, red glands usually common, conspicuous; hypanthium 3.5–4.5 mm diam.; sepals 5–7 mm, apex subacute; petals 6–8 × (4–)5–8 mm, longer than sepals; filaments 0.7–1.2 mm, anthers 0.4 mm; carpels 40–60, apical hairs absent, styles columnar, strongly papillate-swollen in proximal 1/5–1/3, 0.9–1 mm. |
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Achenes | 2 mm. |
1.2–1.8 mm. |
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2n | = 42, 49 (Russian Far East). |
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Potentilla anserina |
Potentilla tikhomirovii |
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Phenology | Flowering summer. | |||||||||||||
Habitat | Dry tundra meadows, loamy soil banks, sedge-herb slopes | |||||||||||||
Elevation | 0–1100 m (0–3600 ft) | |||||||||||||
Distribution |
AK; AZ; CA; CO; CT; IA; ID; IL; IN; MA; ME; MI; MN; MT; ND; NE; NH; NM; NV; NY; OH; OR; RI; SD; UT; VT; WA; WI; WY; AB; BC; MB; NB; NL; NS; NT; NU; ON; PE; QC; SK; YT; Mexico; South America (Argentina, Chile); Eurasia; Pacific Islands (New Guinea, New Zealand); s Australia
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AK; NT; NU; Greenland; Europe (Russia); Asia |
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Discussion | Subspecies 4 or 5 (4 in the flora). Potentilla anserina is polymorphic in most features, especially in hairiness, but also in size and in degree of dissection of leaflets, epicalyx bractlets, and sepals. While most of the variation described by A. G. Blytt (1906) is taxonomically insignificant, A. Rousi (1965) found support for three northern races: subspp. anserina, egedei, and pacifica. He also suggested that P. yukonensis Hultén might qualify as a separate subspecies. This treatment follows J. Soják (1994) in accepting four northern subspecies of P. anserina, all present in North America. A. Rousi (1965) demonstrated partial interfertility between the races of Potentilla anserina, which form intermediates in all zones of contact. The distinctness of the four races, in spite of intermediates, is upheld by being partly allopatric and occupying different habitats where they are sympatric. As partly interfertile parapatric entities, they are best treated as subspecies. The vast majority of chromosome counts are tetraploid. Tetraploid plants (2n = 28) are fully fertile; hexaploids (2n = 42) are largely pollen and seed sterile; pentaploids (2n = 35) are probably occasional hybrids (S. Erlandsson 1942, 1942b; A. Rousi 1965). A. Kurtto et al. (in J. Jalas et al. 1972+, vol. 13) considered numbers above tetraploid level as cases of occasional autopolyploidy. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Potentilla tikhomirovii is an assumed hybrid species combining characteristics from P. arenosa subsp. arenosa of sect. Niveae (abaxial leaflet surfaces with crisped-cottony hairs, adaxial surfaces with both long and short hairs, petioles often with both long and short hairs, and flower shape and size) and P. hyparctica of sect. Aureae (crisped-cottony hairs often not fully covering abaxial leaf surfaces, reddish color in most plant parts, sepals and epicalyx bractlets relatively large, broad, less acute, and with many and reddish glands, which are often also on petioles and stipules). Potentilla tikhomirovii has an interrupted range and is not very coherent morphologically. It forms large populations locally, probably by agamic seed propagation, and is a significant part of the Potentilla variation in northern and northeastern Greenland, Ellesmere Island, and parts of the Brooks Range, northern Alaska. Both the distributional and the morphologic patterns indicate that it has evolved multiple times in different regions, such that it is a borderline case for status as an independent species. Its large populations and significant distribution in some regions support recognition, as also does the paucity of obvious back-crosses with the parents. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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Key |
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Source | FNA vol. 9, p. 127. | FNA vol. 9, p. 201. | ||||||||||||
Parent taxa | Rosaceae > subfam. Rosoideae > tribe Potentilleae > Potentilla > sect. Pentaphylloides | Rosaceae > subfam. Rosoideae > tribe Potentilleae > Potentilla > sect. Niveae | ||||||||||||
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Synonyms | Argentina anserina | |||||||||||||
Name authority | Linnaeus: Sp. Pl. 1: 495. (1753) | Jurtzev: in A. I. Tolmatchew, Fl. Arct. URSS 9(1): 318. (1984) | ||||||||||||
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