Abstract:
For the effective prevention of biological invasions, the pathways responsible for introductions must
be understood and managed. However introduction pathways, particularly for developing nations,
have been understudied. Using the Hulme et al. (2008) pathway classification, we assessed the
South African introduction pathways in terms of the number of introductions, the invasion success of
introduced taxa, how the pathways have changed over time, and how these factors vary for
vertebrates, invertebrates and plants. Pathway and date of introduction, region of origin, distribution
and invasion status data for 2111 alien taxa were extracted from databases. Most alien and invasive
taxa were deliberately introduced and subsequently escaped captivity or cultivation. Pathway
prominence also varied temporally and across organism types. Vertebrates and plants were largely
escapes and although most plant escapes have become invasive, this is not the case for vertebrates.
However the number of new plant and vertebrate escapes has increased over time. Invertebrates
have been deliberately released or unintentionally introduced as contaminants or stowaways. For
invertebrates the number of release, contaminant and stowaway introductions has increased, and
most contaminants and stowaways have become invasive. As effective screening procedures are in
place for invertebrates released for biological control, the major threats for South Africa are from
vertebrate and plant escapes and invertebrate contaminants and stowaways. We recommend
improvements to risk assessment and education to prevent escapes, and prioritised inspection
strategies to reduce stowaway and contaminant introductions. Finally, as introduction pathways and
introduced taxa change temporally, biosecurity decisions need to be informed by information on
current and future pathways.
