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.
