Towards a taxonomic revision of Nemesia Vent.

Abstract

Recent studies on the Scrophulariaceae s. str. show that the tribe Hemimerideae Benth. is the earliest branching phylogenetic lineage. This tribe consists of at least six genera of which Diascia Link. & Otto and Nemesia Vent. are globally probably the best known due to their extensive horticultural uses. Nemesia consists of ±77 species of annuals or perennial herbs to sub-shrubs, endemic to Africa, distributed in southern tropical Africa including Zimbabwe, Mozambique and southern Africa. The centre of highest diversification is in the Western Cape Province, South Africa. The leaves are linear to lanceolate and mostly toothed; flowers are zygomorphic, bi-lipped, with the upper lip consisting of four lobes, the lower lip two lobes; contain a single ligulate to saccate spur (compared to two spurs in closely related Diascia). Due to the annual habit and variously coloured flowers, the genus is ideal for cultivation and hybridization which have led to numerous hybrids being produced. Plants are popular with gardeners as bedding plants, and used in baskets, window boxes and containers. Nemesia has been identified in Programme 2 (Revisions of plant genera) of the Strategy for taxonomic research in South Africa 2015–2020 as one of the genera in need of revision. In this presentation a broad overview of the genus and the scope of the intended taxonomic revision are discussed. The revision will contribute towards filling knowledge gaps through documenting and describing a number of new species, providing updated descriptions, extension of herbarium collections (including sampling for molecular analyses), and updating keys and distribution maps for all species in the genus.