A new species of Polygala (Polygalaceae) from ultramafic soils in Sekhukhuneland, South Africa, with notes on its ecology

Polygala sekhukhuniensis Retief, Siebert & A.E.Van Wyk (Polygala; section Polygala; subsection Heterolophus), a new species with a restricted range in Sekhukhuneland, South Africa, is described, illustrated and compared with other members of the genus. It is a dwarf shrub that can be distinguished by its much-branched habit, sparsely flowered inflorescences, pink alae with darker pink veins, brown to black seed testa, and oblate pollen grains with pronounced opercula. Geographically, P. sekhukhuniensis is confined to heavily eroded localized sites, a natural geomorphological feature of some of the highly water-dispersible soils derived from ultramafic rocks in the valleys of the Steelpoort River and its tributaries in the Sekhukhuneland Centre of Plant Endemism. P. sekhukhuniensis is a calciotrophic excluder of heavy metals that accumulates Ca in its leaves. It is ecologically compared with co-occurring species of Polygala on ultramafic-derived soil.