Molecular phylogenetics and origins of southern African Oxalis

Despite being a speciose component of the Cape Floristic Region at the southern tip of Africa, the southern African Oxalis lineage is systematically poorly understood. Palynological and preliminary phylogenetic studies of the group contrast with the current taxonomy, and indicate the need for further research. Here we present a largescale phylogenetic analysis comprising 150 of ± 210 southern African species, sampled for plastid trnL–F and trnS–G and nuclear ITS markers, using three different inference methods. Secondly, we explore the origins of southern African Oxalis as a potential Cape clade. Despite substantial localised incongruence between plastid and nuclear datasets, analyses agreed on a monophyletic southern African clade, which consists of two species–poor and one extremely species–rich lineages. The current taxonomy is shown to be artificial, with not one section retrieved as monophyletic. Our topologies are consistent with previous palynological and phylogenetic studies, and provide a backbone for future systematic work. Reconstructions of ancestral area for the southern African lineage support an origin within or close to the Cape Floristic Region.