Warneckea parvifolia (Melastomataceae–Olisbeoideae), a new “sand-forest” endemic from northeastern KwaZulu-Natal (South Africa) and southernmost Mozambique, and a phylogenetic analysis of eastern and southern African representatives of W. section Warneckea

Abstract

Warneckea populations from “sand-forest” or “sand-thicket” habitats in Tembe Elephant Park, South Africa, and Licuati Forest Reserve in adjacent southern Mozambique were previously thought to be a small-leaved form of W. sousae, which typically includes larger-leaved plants ranging from central Mozambique northward to Tanzania. We examine this hypothesis using molecular and morphological evidence. Maximum-likelihood phylogenetic analysis of combined nrDNA ETS and ITS sequence data failed to resolve W. sousae and the Maputaland populations as an exclusively monophyletic group. Instead, the Kenyan endemic W. mouririifolia was strongly supported as the sister species of W. sousae, and the Maputaland plants were resolved in a separate, strongly supported clade together with populations of an as-yet undetermined Warneckea species from northern Mozambique. A hypothesis of exclusive monophyly for the plants from Tembe and Licuati had moderate support in separate ETS and ITS1 analyses (bootstrap proportions of 88% and 81%, respectively). Statistically significant differences in leaf dimensions and internode length were found between the Maputaland plants and typical W. sousae. We conclude that the populations from Tembe and Licuati represent a distinct species, which we describe as W. parvifolia. The species differs from W. sousae in having shorter internodes (mostly 5–25mm not 10–60mm long), smaller leaves (mostly 14–32×8–19mm not 40–76×22–52mm), shorter petioles (mostly 1–1.5mm not 1.5–6mm long), smaller flowers (hypanthium 1×1.5–1.75mm not 1.5–2×2mm; calyx lobes 0.5mm not 0.75mm long; staminal filaments 3–4mm not 5mm long; style 4–5mm not 9mm long), and globose fruit (not obovoid). An IUCN conservation status of Endangered (EN) B1a, b(ii, iii) is indicated for W. parvifolia, due to its limited distribution and projected declines in its habitat quality and area of occupancy.