Biosystematic revision of the native and naturalised species of Rubus L. (Rosaceae) in the Cape Floristic Region, South Africa

Rubus L. is a highly diverse and taxonomically complex genus with a worldwide distribution. Although southern Africa is not a major centre of Rubus diversity, a number of indigenous and naturalised taxa have been recorded from the region, although their taxonomy, nomenclature and evolution are either confused or poorly studied at best. This paper represents the first results of a wider project focusing on the biosystematics of the southern African Rubus flora, and presents a taxonomic revision of the brambles of the Cape Floristic Region, including an estimation of ploidy levels. A total of eight taxa are recognised, including the two indigenous taxa R. pinnatus and R. rigidus agg., the four introduced species R. armeniacus, R. bergii, R. rosifolius and R. titanus, and two hybrids between indigenous and introduced taxa. Rubus rigidus agg. is an unresolved and variable species complex with at least two ploidy levels (5x, 6x). The hybrid taxon R. bergii × R. rigidus appears to be widespread and behaves as an independent apomictic complex. In addition, hybridization between R. bergii and R. pinnatus is relatively common in the contact zones between the two species. The two introductions Rubus armeniacus and R. titanus are recorded from South Africa for the first time. The invasive potential of the introduced species is regarded as low but the potential for hybridization by R. bergii seems to be high. An identification key, morphological descriptions, and notes on nomenclature, distribution and ecology are provided, and all taxa are illustrated.