FNA: Ivesia gordonii var. alpicola vs. Ivesia sect. Ivesia

Phenology

Flowering summer.

Habitat

Dry grassy areas on talus, or gravelly or rocky slopes and ridges, in subalpine and alpine montane conifer woodlands, alpine tundra

Elevation

2100–3300 m (6900–10800 ft)

Distribution

CA; ID; MT; OR; WA

w United States

Discussion

P. A. Rydberg (1898) used var. alpicola (as Horkelia gordonii var. alpicola) for compact, high-elevation plants throughout the range of Ivesia gordonii. As circumscribed here, var. alpicola is restricted to plants occurring disjunctly in an arc around the northwestern part of the species range. Populations occur in the northern Coast Ranges and central Sierra Nevada of California, sporadically to Mount Adams and the Wenatchee Mountains in Washington, and from there to the mountains of central Idaho and the Bitterroot Range of Montana. The variety is also disjunct on the Owyhee Mountains of southwestern Idaho.

Plants of var. alpicola average shorter than those of var. gordonii, which occurs farther east and south. In var. alpicola, stems with only glandular indumentum are common; such stems are rare in var. gordonii. Unlike those of var. gordonii, the leaflets of var. alpicola are frequently glandular with only marginal hairs.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Species 8 (8 in the flora).

Species in sect. Ivesia tend to form compact rosettes or tufts in open montane to alpine areas, often where rocky but generally not growing in rock crevices (except Ivesia longibracteata). General characteristics of the section are an overall evident glandularity, loosely to tightly cylindric leaves (mousetail-like in I. muirii), relatively short ascending to erect stems, straight pedicels, and flowers that are typically congested into 1–few capitate clusters that sometimes become more open in fruit. The taproots of some species, especially I. lycopodioides, are markedly enlarged, an adaptation to alpine growing conditions. The inclusion of two anomalous species in the section, I. longibracteata and I. webberi, is tentative; it is also possible that I. cryptocaulis belongs here rather than in sect. Setosae.

Section Ivesia has its center of species diversity in the high Sierra Nevada of California, where Ivesia pygmaea, with its ten stamens and more open habit, is possibly transitional between sects. Ivesia and Setosae. Ivesia gordonii (the most widespread species), I. tweedyi, and I. utahensis form an arc around the northern Great Basin, as outliers from the core Sierran distribution of the section.

Some early floras treated Ivesia pygmaea and I. lycopodioides as varieties of I. gordonii (for example, W. H. Brewer et al. 1876–1880, vol. 1) or Potentilla gordonii (Hooker) Greene (W. L. Jepson [1923–1925], 1909–1943, vol. 2). Recent treatments follow D. D. Keck (1938) in recognizing all three as distinct species; some annotations and references are nevertheless carried over from the earlier expanded circumscription of I. gordonii.

Since Ivesia cryptocaulis is sometimes identified as a member of sect. Ivesia, it is included herein and keys out in the seventh couplet.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key

1. Epicalyx bractlets longer than sepals, 2.5–5 mm; leaves weakly planar to loosely ± cylindric; leaflets 5–6 per side; Castle Crags, n California.	I. longibracteata
1. Epicalyx bractlets shorter than sepals, 0.5–3(–4 in I. gordonii) mm; leaves loosely to tightly cylindric; leaflets mostly 10–40 per side (4–10 in I. webberi); w United States	→ 2
2. Plants silvery; leaves very tightly cylindric (mousetail-like, with leaflets scarcely distinguishable); leaflets 0.4–1 mm.	I. muirii
2. Plants ± green; leaves loosely to tightly cylindric; leaflets distinguishable, (0.5–)2–13(–18) mm	→ 3
3. Cauline leaves 2, paired; basal leaves: leaflets 4–8(–10) per side; petiole hairs 2–4 mm.	I. webberi
3. Cauline leaves 0–2(–3), not paired; basal leaves: leaflets (6–)10–35 per side; petiole hairs 0.2–1.5 mm	→ 4
4. Hypanthia turbinate to campanulate, (1.5–)2–4(–4.5) mm (± as deep as wide); petals narrowly oblanceolate to narrowly spatulate.	I. gordonii
4. Hypanthia shallowly cupulate or shallowly campanulate, 1–2 mm (wider than deep); petals oblanceolate or broadly elliptic to spatulate or broadly obovate	→ 5
5. Carpels (1–)2–6(–9); Idaho, Utah, Washington	→ 6
5. Carpels (5–)8–30; e California, Nevada	→ 7
6. Petals white, sometimes pink-tinged; stems prostrate to ascending; leaflets 2–4 mm; Utah.	I. utahensis
6. Petals golden yellow; stems ascending to erect; leaflets 4–7(–10) mm; n Idaho, Washington.	I. tweedyi
7. Plants diffusely matted; Spring Mountains, s Nevada.	I. cryptocaulis
7. Plants rosetted to tufted or ± tightly matted; Sierra Nevada, White Mountains, and Sweetwater Mountains of e California and adjacent w Nevada	→ 8
8. Stamens 10; sheathing bases usually ± strigose abaxially; taproots stout, not fleshy.	I. pygmaea
8. Stamens 5; sheathing bases glabrous abaxially; taproots fusiform, fleshy.	I. lycopodioides