Invasive amphibians in South Africa

Invasive amphibians in South Africa
G. John MEASEY1, Giovanni Vimercati1, Sarah J. Davies1
1Centre for Invasion Biology, Department of Botany & Zoology, Stellenbosch University, Stellenbosch, South Africa

Globally, invasive amphibians are known for their environmental and social impacts that range from toxicity to local fauna and human populations, to direct predation on other amphibians. Although several countries on most continents of the globe have had multiple introductions from many species, South Africa appears to have escaped from allochthonous introductions but instead has a small number of domestic exotics: Hyperolius marmoratus, Sclerophrys gutturalis and Xenopus laevis. Here we present updated information on the invasion of all three South African domestic exotics, and ask how their invasion pathways differ. In each case, genetic studies show human-mediated initial introduction which is generally unintentional, and perhaps unsurprisingly all species have an element of leap-frog dispersal between artificial impoundments. However, the movement of South African frogs has not always been unintentional, and intentional introduction of X. laevis for scientific and medical purposes has resulted in invasions by this species on four continents. Results from a survey of stowaway amphibians entering and moving around South Africa suggest that while this is still an unusual phenomenon, there are indications of increasing numbers of amphibians being imported into the country. This increase in propagule pressure suggests that preventing new introductions will become a key challenge for the future. Despite the low numbers of invasive species, South Africa is currently the most highly invaded for amphibian species on the African content.