FNA: Portulacaceae vs. Phemeranthus

Distribution

Primarily Southern Hemisphere; poorly represented in Eurasia

North America; Central America; South America

Discussion

Genera 20–30, species ca. 500 (9 genera, 91 species in the flora).

The eastern New World species of Portulacaceae seem to have a closer relationship with the African species, and the western New World species a closer one with the Australian species, than the two New World groups have with each other to each other.

The outer perianth segments, referred to herein as sepals, are held by some (e.g., T. Eckardt 1976) to be modified bracteoles, the petals then representing the true sepals. However, the traditional interpretation, adopted here and in most North American floras, still finds current support (R. C. Carolin 1987). A comparable situation prevails with respect to the cauline leaves in Claytonia and other genera, which are widely interpreted to be foliaceous bracts (R. C. Carolin 1987); here again, as is appropriate in a descriptive context, the traditional terminology is employed. In Talinopsis and Portulaca, the stipular nature of the nodal or axillary hairs also has been a matter of discussion. The question was revisited by R. Geesink (1969), who denied their stipular origin.

The relationships of the family are not a matter of dispute (A. Cronquist 1981; R. C. Carolin 1987); the same cannot be said for the relationships and delimitations of the genera, which have always been labile. They are, at present, the subject of active research, which has led to the current acceptance of Phemeranthus and Cistanthe. Changes in the generic classification are discussed in the treatments of the genera concerned.

Because of the uncertain relationships, the genera and species are listed alphabetically.

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

Species 25–30 (16 in the flora).

C. S. Rafinesque (1814b) transferred Pursh’s Talinum teretifolium, which had been described earlier that year and was the only North American species then attributed to that primarily Old World genus, to the segregate genus Phemeranthus. Since then, though, most other authors have continued to recognize that species within Talinum, along with other similar and exclusively New World taxa described subsequently, as sect. Phemeranthus. However, a fairly strongly correlated set of differences in the leaf, pollen, fruit, and seed structures of these species compared with those of sect. Talinum, only two species of which are found in North America, supports their recognition at the generic level (R. Carolin 1987, 1993; M. A. Hershkovitz 1993). Complementary to the morphological evidence, recent molecular studies (M. A. Hershkovitz and E. A. Zimmer 1997, 2000; W. L. Applequist and R. S. Wallace 2001) indicate that Phemeranthus is phylogenetically distinct from Talinum.

Positive identification of Phemeranthus specimens often requires examination of both flower and fruit, including seeds (with hand lens). Fortunately, the flowers develop successively and the capsules mature rapidly after anthesis, so both flowers and fruits will be present on a given plant during most of the reproductive season.

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

Key

1. Ovary half-inferior to inferior	Portulaca
1. Ovary superior	→ 2
2. Subshrubs; stem nodes pubescent	Talinopsis
2. Herbs; stem nodes glabrous	→ 3
3. Capsule dehiscence circumscissile, valves longitudinally dehiscent from base	→ 4
3. Capsule dehiscence not circumscissile, valves longitudinally dehiscent from apex	→ 5
4. Petals 25-40 mm; seeds strophiolate; nc Washington to extreme sc British Columbia	Cistanthe
4. Petals 4-26 mm (15-35 mm in Lewisia rediviva); seeds estrophiolate; more widespread	Lewisia
5. Stigmas 2; capsule valves 2	Cistanthe
5. Stigmas 1 or 3; capsule valves 2-3	→ 6
6. Sepals mostly deciduous; inflorescences not appearing secund; leaves articulate at base, attachment points round, not clasping; capsule valves wholly or partly deciduous	→ 7
6. Sepals persistent; inflorescences somewhat to markedly secund (at least distally); leaves not articulate at base, attachment points linear, somewhat to markedly clasping; capsule valves not deciduous	→ 8
7. Leaf blades broadly planate, 1-7 cm wide; capsules tardily dehiscent, valves or portions of them sometimes persistent; exocarp and endocarp distinctly differentiated, sometimes separating; seeds minutely tuberculate or striolate, strophiolate, not covered by membrane	Talinum
7. Leaf blades terete or semiterete, 1-3 mm wide, (narrowly planate, 1[-2] cm wide in Phemeranthus aurantiacus); capsules promptly dehiscent, valves deciduous; exocarp and endocarp not evidently differentiated and not separating; seeds smooth, rugulose, or distinctly ridged, estrophiolate, covered by thin, fleshy to chartaceous membrane	Phemeranthus
8. Ovules and seeds (1-)7-40	→ 9
8. Ovules 3 or 6; seeds 1-6	→ 10
9. Leaves and sepals sometimes with elongate, unicellular hairs; sepals distinctly angular or keeled; capsule valves reflexed after dehiscence, margins markedly involute	Calandrinia
9. Leaves and sepals without elongate, unicellular hairs; sepals not distinctly angled or keeled; capsule valves not reflexed after dehiscence, margins not markedly involute	Cistanthe
10. Cauline leaves 2 (rarely 3 in whorl), distinct or partially or completely connate; ovules 3 or 6	Claytonia
10. Cauline leaves more than 2, distinct; ovules 3	Montia

1. Petals yellow, orange, or reddish or pinkish orange	→ 2
1. Petals white, pink, or purplish (sometimes tinged pale yellow in P. sediformis)	→ 4
2. Flowers usually solitary, sometimes 2-3-flowered cymules in leaf axils	P. aurantiacus
2. Flowers in cymes borne on scapelike peduncles	→ 3
3. Leaves sessile, not appearing petiolate	P. humilis
3. Leaves sessile but appearing petiolate	P. marginatus
4. Seeds with arcuate ridges	P. longipes
4. Seeds without arcuate ridges	→ 5
5. Seeds corrugate-rugulose	P. rugospermus
5. Seeds smooth	→ 6
6. Stamens usually 5	P. parviflorus
6. Stamens usually 7 or more	→ 7
7. Stigmas 3	P. brevifolius
7. Stigma 1	→ 8
8. Stems bearing persistent midribs of old leaves	→ 9
8. Stems not bearing persistent midribs of old leaves	→ 10
9. Persistent midribs ± straight, spinelike, 5 mm or more	P. spinescens
9. Persistent midribs arcuate, bristlelike, less than 5 mm	P. sediformis
10. Sepals deciduous after anthesis	→ 11
10. Sepals persistent through capsule development	→ 12
11. Petals 9-15 mm; stamens 40 or more	P. mengesii
11. Petals 5-7 mm; stamens 12-20	P. teretifolius
12. Stamens fewer than 20	→ 13
12. Stamens usually 20 or more	→ 14
13. Peduncles 1 cm or shorter; capsules ellipsoid	P. thompsonii
13. Peduncles longer than 1 cm; capsules ovoid	P. validulus
14. Peduncles not scapelike, shorter than 2 cm	P. brevicaulis
14. Peduncles scapelike, much longer than 2 cm	→ 15
15. Sepals 3-4 mm; petals 8-10 mm	P. calcaricus
15. Sepals 4-6 mm; petals 10-15 mm	P. calycinus