Taxonomic Status of Acleisanthes, Selinocarpus, and Ammocodon (Nyctaginaceae)

Recent molecular and morphological studies suggest that neither Acleisanthes nor Selinocarpus (Nyctaginaceae) are monophyletic as currently circumscribed. Further, these data provide no basis for continued recognition of the monotypic genus Ammocodon as separate from these other two genera. Therefore, all 8 Selinocarpus species and the monospecific Ammocodon are transferred to Acleisanthes; 3 additional Selinocarpus species are reduced to synonymy. The genus Acleisanthes is now composed of 16 species, distributed primarily in the Chihuahuan Desert of North America. Diagnostic features of Acleisanthes include an herbaceous or woody perennial habit in arid environments, and the presence of both cleistogamous and chasmogamous flowers often simultaneously on an individual plant. Further, flowers are usually axillary and subtended by 1 to 4 subulate bracts, with chasmogamous flowers frequently white or yellow and funnelform to salverform.