FNA: Aphanes vs. Rosaceae tribe Potentilleae

Distribution

North America; nw Mexico; Eurasia; n Africa [Introduced in s South America, Pacific Islands, Australia]

North America; Mexico; Central America; South America; West Indies; Bermuda; Eurasia; Africa; Atlantic Islands; Pacific Islands; Australia

Discussion

Species ca. 20 (3 in the flora).

On the basis of molecular studies, R. Gehrke et al. (2008) have suggested that Aphanes and the Central America and South American Lachemilla (Focke) Rydberg should be included in a more broadly circumscribed Alchemilla. Both Aphanes and Lachemilla were shown to be monophyletic groups as is Alchemilla, apart from the African species currently placed in that genus; these form a clade separate from Alchemilla as represented in North America and Eurasia. The African species deserve more thorough investigation before such a morphologically distinct genus as Aphanes is abandoned.

The highly reduced nature of plants of Aphanes, coupled with their high dispersibility, complicates circumscription of species in the genus. The most recent treatments recognize a number of endemic species in South America, Europe, and North Africa, particularly in regions with Mediterranean climates. The extent to which these, and those recognizable in western North America, represent native radiations versus multiple introductions remains to be determined.

Measurements of flowers apply collectively to the length of the hypanthium and calyx measured in fruit.

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

Genera 14–22, species ca. 860 (14 genera, 189 species, including 1 hybrid, in the flora area).

The base chromosome number for Potentilleae is mostly x = 7 (8 in Alchemilla and Aphanes; 14 in Comarum).

Variation in the number of genera recognized in Potentilleae is due to differences in generic delimitation between D. Potter et al. (2007) and the authors of Potentilla and segregates here (see 9. Ivesia and 8. Potentilla for discussion). In the former, Duchesnea, Horkelia, Horkeliella, and Ivesia are included within Potentilla. Likewise, Aphanes is included within Alchemilla by Potter et al. while it is kept distinct here.

Potentilla and its segregates and Fragaria are host to Phragmidium rusts, but not the other genera of the tribe.

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

Key

1. Flowers 1.5–2.5 mm in fruit, sepals ± spreading to erect; leaf blades 4–10 mm; petioles free from stipules in proximal and distal leaves; stems 2–20(–30) cm; at least some hairs more than 1 mm; most stipule lobes on distal nodes ± triangular, 1–2(–4) times as long as wide.	A. arvensis
1. Flowers 1–1.5 mm in fruit, sepals connivent to spreading; leaf blades 2–5 mm; petioles adnate to stipules in distal leaves; stems 1–10(–22) cm; hairs less than 1 mm; most stipule lobes on distal nodes oblong or ovate, usually 2/3–1 times as long as wide	→ 2
2. Inflorescences dense, flowers tending to remain hidden; pedicels usually less than 1 mm; sepals 0.2 mm, connivent; epicalyx bractlets minute (less than 0.1 mm) or absent; stipules overlapping, lobes oblong, almost equal to undivided portion; leaf blades 5 mm, divided into 3 segments.	A. australis
2. Inflorescences open, flowers tending to become exposed; pedicels to 2 mm; sepals 0.2–0.6 mm, connivent to spreading; epicalyx bractlets 0–0.5 mm; stipules overlapping only distally, lobes ovate, 2/3–1 times undivided portion; leaf blades 2–5 mm, 4–6-lobed.	A. occidentalis

1. Shrubs; leaf lobe margins entire; achenes hirsute.	Dasiphora
1. Herbs, perennial, sometimes annual or biennial, or subshrubs; leaf lobe margins or apices ± toothed, sometimes entire; achenes glabrous (sometimes ± hairy)	→ 2
2. Petals 0, sepals 4; achenes 1, enclosed in dry, urceolate or subglobose to ellipsoid or ovoid hypanthia	→ 3
2. Petals and sepals usually 5; achenes 1–260, usually aggregated (sometimes on elongating tori), usually in (± open) patelliform, cupulate, campanulate, or turbinate hypanthia (not enclosed in dry hypanthium)	→ 4
3. Herbs perennial; leaves basal, blades reniform to orbiculate, palmately lobed, sometimes palmately compound; stamens 4.	Alchemilla
3. Herbs annual; leaves cauline, blades cuneate, deeply divided into segments, each lobed; stamen 1(or 2).	Aphanes
4. Leaves all or mostly basal or proximal (if cauline, deeply pinnatifid), ternate or 2–4-ternate (sometimes simple and coarsely toothed apically in Sibbaldia)	→ 5
4. Leaves basal or cauline, the latter usually reduced distally, odd-pinnate to palmate, rarely ternate or ± bipinnate	→ 9
5. Tori becoming red and fleshy in fruit; leaf margins serrate to crenate	→ 6
5. Tori hemispheric (not enlarged or fleshy) in fruit or absent; leaf margins entire or (2–)3(–5)-toothed apically	→ 7
6. Leaves ± doubly serrate or crenate; stolons leafy; inflorescences: flowers solitary, axillary at stolon nodes; petals yellow.	Duchesnea
6. Leaves serrate to crenate; stolons not leafy; inflorescences 1–10-flowered, cymes, axillary from leaf rosettes; petals usually white.	Fragaria
7. Leaves pinnately compound or simple and deeply pinnatifid, margins entire, stipules absent.	Chamaerhodos
7. Leaves ternate, margins toothed apically, stipules persistent	→ 8
8. Petals ± yellow; stamens 5.	Sibbaldia
8. Petals usually white; stamens 20(–30).	Sibbaldiopsis
9. Petals deep red to purple, rarely pink, shorter than sepals; tori enlarged and spongy at maturity; horizontal stems sometimes floating, wetland habitats.	Comarum
9. Petals yellow to white, rarely pink or red (then equal to or longer than sepals); tori not enlarged and spongy at maturity; stems erect to decumbent, not horizontal or floating even if in wetlands	→ 10
10. Anthers dehiscing by continuous marginal slit (with a single theca); styles sub-basal.	Drymocallis
10. Anthers dehiscing longitudinally; styles subterminal to lateral	→ 11
11. Hypanthium patelliform to campanulate or cupulate to turbinate (not flat-bottomed); filaments not forming tube; petals white to yellow, sometimes reddish or pink tinged	→ 12
11. Hypanthium ± cupulate or bluntly campanulate and flat-bottomed; filaments forming tube; petals usually white, sometimes pink-tinged, rose-veined, or cream	→ 13
12. Plants not aromatic; leaves ± cordate or reniform to narrowly elliptic in outline, leaflets 3–15(–41); petals oblanceolate or obovate to obcordate to nearly round, rarely elliptic; carpels 3–260.	Potentilla
12. Plants often aromatic; leaves planar to cylindric, leaflets (3–)7–161; petals linear or narrowly oblanceolate to obovate, sometimes obcordate; carpels 1–20(–40).	Ivesia
13. Stamens 10; leaflets (3–)5–41.	Horkelia
13. Stamens 20; leaflets 30–70.	Horkeliella