Reassessment of the taxonomic status of Oxalis fabaefolia (Oxalidaceae) and the description of a unique variety of Oxalis flava from the Northern Cape Province of South Africa

Southern African Oxalis taxonomy is complicated by tremendous morphological variation. The widely distributed Oxalis flava, for example, currently contains eight morphologically distinct forms. The remaining members of sect. Crassulae display morphological characters distinctive enough to retain specific status, despite resemblance to forms of the broadly defined O. flava. Recent collection of a taxon with strong morphological affinities to species in sect. Crassulae generated much interest. In this study we assess the placement of this new taxon to members of sect. Crassulae based on analyses of DNA sequence data of the Internal Transcribed Spacer (ITS) region and morphological comparisons. Results show that most members of sect. Crassulae are distantly related to O. flava. However, our morphological and molecular data strongly suggested that the newly collected taxon represents yet another form of O. flava. In addition, these data show O. fabaefolia to be nested within O. flava, suggesting that it should be synonymised under this broadly defined species. Both the new taxon and O. fabaefolia display unique morphological characters, allowing them to be considered separate subspecific taxa of O. flava. Thus the taxa O. flava var. fabaefolia and O. flava var. unifoliolata are here proposed.