Xenostegia linearifolia (Convolvulaceae), a new species from Zambia.

Xenostegia is a small genus of Convolvulaceae, first circumscribed in 1980 based on two species, X. tridentata and X. medium. A reclassification of Merremia s.l. and its allied genera resulted in the inclusion of three more species, X. alatipes, X. pinnata and X. sapinii, and, more recently, a new species was described from central Africa, X. lomamiensis, bringing the currently accepted species to six. Of these, five are restricted to the African continent and Madagascar, with one, X. tridentata, more widespread, extending into southeast Asia and Australia. Xenostegia can be recognised for the prostrate and twining habit, angular, narrowly winged stems, sessile leaves, yellow to white corolla, longitudinally dehiscing anthers and non-spinulose pantoaperturate pollen. However, as our understanding of this genus progresses, more variation is found and new species are discovered. Here, a new species of Xenostegia from Zambia is described, with erect habit and linear leaves, which has never been reported in the genus. So far, the species is known from only one location, seemingly threatened by urbanisation, and is preliminarily assessed as Critically Endangered.