Revised delimitation of the genus Tetraria, nom. cons. prop. (Cyperaceae, tribe Schoeneae, Tricostularia clade)

Tetraria as currently circumscribed still is a polyphyletic genus restricted to the southern hemisphere. Besides several small independent evolutionary lineages, two larger multispecies lineages have been recognised from South Africa, identifiable by key morphological differences: the c. 30 Tetraria species in the Tricostularia clade tribe Schoeneae have noded culms and a reticulate tunic surrounding the culm base, while the c. 17 Tetraria species in the Schoenus clade of tribe Schoeneae have a culm without nodes and lack reticulate sheaths at the culm bases. Recently, both the 17 non-reticulate Tetraria species (including the original type of the genus, T. thuarii) and seven species of the closely related genus Epischoenus were transferred into Schoenus. This left the c. 30 species of the other lineages of Tetraria s.l. in need of new names. For nomenclatural consistency and since Tetraria, in particular the group known as reticulate-sheathed Tetraria, represent an important and well-known plant group of the Cape Floristic Region, a conservation proposal was submitted to conserve Tetraria with a new type, i.e. T. thermalis, which is part of the reticulate-sheathed Tetraria clade. This study presents a redelimitation of Tetraria, nom. cons. prop. reflecting the recent taxonomic changes, and formally transfers five species of Costularia subgenus Lophoschoenus and one species of Epischoenus to Tetraria.