The genus <i>Echium</i> (Boraginaceae) in southern Africa

Abstract

The genus Echium L. (Boraginaceae) comprises about 60 species, mainly from Macaronesia. Europe, western Asia and North Africa. Two species E plantagineum L. and E. vulgare L. were introduced into southern Africa and have become naturalised. The species occur mainly as roadside weeds in the region. Echium is closely related to Lobostemon Lehm. (incl. Echiostachys Levyns), endemic in the southwestern Cape region. Pollen morphology shows a remarkable similarity between these genera, even suggesting that they could be merged. However, other characters, such as bilobed styles (Echium) versus undivided ones (Lobostemon) and the presence of an annulus, composed of a minute collar or 5-10 minute hairy lobules, at the bottom of the corolla tube inside (Echium), in contrast to hairs and/or scales at the base of the filaments (Lobostemon) contradict the pollen structure, and Echium and Lobostemon are therefore regarded as two separate genera. Significant taxonomic characters, an identification key, full descriptions, illustrations and distribution maps of E. plantagineum and E. vulgare are given.

Keywords

• Boraginaceae
• <i>Echium</i> L.
• indumentum
• <i>Lobostemon</i> Lehm.
• phytogeography
• pollen
• relationships
• southern Africa
• taxonomy
• weed