Abstract
This chapter provides the first assessment of South African native vascular plants as naturalised and invasive species in other parts of the world. For naturalised species, Global Naturalized Alien Flora (GloNAF) data were used, while for invasive species an assessment was made using the peer-reviewed literature, experience of the authors, and correspondence with authorities in many parts of the world.
Results show that 1093 South African native plant taxa have been recorded as naturalised, but for only 79 of these is there strong and unequivocal evidence of invasiveness in natural or semi-natural ecosystems (another 132 taxa have been listed as invasive, but do not fulfil all criteria for listing as such). Thirty-five taxa have naturalised in more than 100 regions (countries, states, provinces, districts, or individual islands), and six taxa (all grasses-family Poaceae) are naturalised in more than 200 regions.
However, of these, only 12 (34.2%) are recorded as invasive, and only nine fulfil the more conservative definition of invasive. These figures indicate that to be widely distributed does not automatically translate into being a strong invader, and that taxa that are extremely successful as invaders in some regions only succeed in specific environmental and geographic settings, and many of them are not widespread alien plants.
Grasses are over-represented among both naturalised and invasive South African plant exports: 15% of naturalised species and 23% of invasive species are grasses. Temperate Asia and Europe are net donors of naturalised plants to South Africa, but Australasia and the Pacific Islands have received many more naturalised plants than they have donated to South Africa.
Of taxa native to South Africa recorded as unequivocally invasive outside of cultivation elsewhere, 65% occur in Australia.