Flora of North America species comparison

A cladistic analysis of chloroplast ndhF sequence data (W. L. Applequist and R. S. Wallace 2001) indicated that Phemeranthus aurantiacus belongs in the same clade as Talinum paniculatum (Jacquin) Gaertner and the two other species of that genus that were sampled, rather than in a separate and rather distant clade containing P. mengesii, the only other species of Phemeranthus included in the study. The molecular evidence, together with the planate leaves and extended stem of P. aurantiacus, which are anomalous in Phemeranthus, suggest that perhaps this species should be restored to Talinum. However, in fruit and seed characters, the chief morphological bases on which Talinum and Phemeranthus are distinguished, P. aurantiacus clearly belongs in the latter.

Talinum angustissimum often has been held separate from Phemeranthus aurantiacus (T. aurantiacum), but the supposed distinctions break down in a continuum of intergradation, the other extreme of which was described as T. whitei. The former extreme, centered in southern Arizona, has yellow petals, very narrow leaves, slender stems, and small, globose capsules; the latter, centered in southern Chihuahua and northern Durango, has orange to reddish petals, broad leaves, stout stems, and large, ovoid capsules. The name T. lineare Kunth, which properly applies to a species from central Mexico, has been misapplied to some collections of P. aurantiacus from Texas.

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

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.)