A taxonomic revision of the Cotula barbata group (Anthemideae, Cotulinae, Asteraceae)

Abstract

• Seven species recognized. • One new species described ( Cotula tuberculata Jakoet & Magee). • Cotula melaleuca Bolus is here reduced into synonymy with C . barbata DC. • C. leptalea DC. and C. tenella E Mey ex DC. are here reduced into synonymy with C. laxa DC. • Detailed morphological descriptions, typification, illustrations of diagnostic characters and distribution maps indicating the known geographical ranges of these species are included. A taxonomic revision of the Cotula barbata group is presented. At the onset of the study nine species were recognised within this group, which is defined by a combination of an annual life history, usually homogamous discoid capitula, mostly basal leaves that are not sheathing at the base, and naked peduncles that are not inflated apically. These species are restricted to the Greater Cape Floristic Region of South Africa. The species are variable in cypselae morphology, which is shown herein to be taxonomically informative. Through extensive investigation, we here recognize seven species, one of which is described as new. Cotula melaleuca Bolus is reduced into synonymy with C. barbata DC. , C. leptalea DC. and C. tenella E Mey ex DC. are reduced into synonymy with C. laxa DC., and C. tuberculata Jakoet & Magee is described as new. An identification key is provided for the seven species, with detailed morphological descriptions, typification, illustrations of diagnostic characters and distribution maps.