The pathways of introduction for alien species in South Africa and the consequences for management

The pathways of introduction for alien species in South Africa and the consequences for management
Katelyn T. Faulkner1,2, Mark P. Robertson2, Mathieu Rouget3, John R. Wilson1,4
1Invasive Species Programme, SANBI; 2Centre for Invasion Biology, University of Pretoria; 3Centre for Invasion Biology, University of KwaZulu-Natal; 4Centre for Invasion Biology, Stellenbosch University

Preventing the introduction of alien species is often more cost effective than managing them after introduction. To this end, research on the pathways of introduction is a vital management tool and can be used to develop preventative strategies, early detection methods and import regulations that target the most efficient pathways of introduction. We used data on pathways of introduction, date of introduction, and invasion success to evaluate the pathways of introduction for vertebrates, invertebrates  and  plants  introduced  to  South  Africa.  We  found  that  the  escape  pathway  has introduced the most organisms to South Africa, as well as the majority of South Africa’s invaders. Additionally, the importance of the pathways varies across organisms and over time. For vertebrates and plants the escape pathway is dominant and has increased in importance over time. However, vertebrate escapees have a low likelihood of becoming invasive, and plant escapees are no more likely to be successful invaders than plants utilizing other pathways. The release, contaminant and stowaway pathways have introduced the majority of invertebrates, and for these organisms have not only increased in importance over time but have also introduced successful invaders. In South Africa, the prominence of invertebrate releases demonstrates the effectiveness of biological control programmes. But, vertebrate and plant escapes as well as invertebrate contaminants and stowaways represent a real threat to South African biosecurity.