Expansion of Schlechteranthus (Ruschioideae, Aizoaceae) to include Polymita, with a new species from Namaqualand, South Africa

•Polymita N.E.Br. is included in Schlechteranthus Schwantes.•A new species of Schlechteranthus, S. holgatensis Klak, is described.•Distributions of the six species of Schlechteranthus rarely overlap.•Species show differences in flowering time and ecological preferences.

The species of Polymita N.E.Br. and Schlechteranthus Schwantes are compact, highly succulent shrubs endemic to the arid, winter-rainfall region of northern Namaqualand, South Africa. The two genera are closely related, and this is reflected in their overall similarity. Characters formerly believed to separate Polymita and Schlechteranthus are shown to vary considerably and therefore we include Polymita within Schlechteranthus. Schlechteranthus diutinus (L. Bolus) Klak, previously included under Polymita albiflora (L. Bolus) L. Bolus, exhibits consistent differences from P. albiflora in the leaves and is reinstated. We describe a new species, Schlechteranthus holgatensis Klak, which is known from a single, very prolific locality along the Holgat River in northern coastal Namaqualand. The new species is unusual for its velvety leaves: all other Schlechteranthus have smooth and somewhat shiny leaves. The habit and fruits, however, firmly place this species in Schlechteranthus. Altogether, six species are recognized and a revised generic description is provided. The ranges of the species rarely overlap and they mostly inhabit distinct soil types and occur at different altitudes. Species which occur close together flower at different times.