Abstract:
BACKGROUND : The sub-Antarctic Prince Edward Islands (PEIs), South Africa’s southernmost
territories have high conservation value. Despite their isolation, several alien species have
established and become invasive on the PEIs.
OBJECTIVES : Here we review the invasion ecology of the PEIs.
METHODS : We summarise what is known about the introduction of alien species, what
influences their ability to establish and spread, and review their impacts.
RESULTS : Approximately 48 alien species are currently established on the PEIs, of which 26 are
known to be invasive. Introduction pathways for the PEIs are fairly well understood – species
have mainly been introduced with ship cargo and building material. Less is known about
establishment, spread and impact of aliens. It has been estimated that less than 5% of the PEIs
is covered by invasive plants, but invasive plants have attained circuminsular distributions on
both PEIs. Studies on impact have primarily focussed on the effects of vertebrate invaders, of
which the house mouse, which is restricted to Marion Island, probably has the greatest impact
on the biodiversity of the islands. Because of the risk of alien introductions, strict biosecurity
regulations govern activities at the PEIs. These are particularly aimed at stemming the
introduction of alien species, and are likely to have reduced the rates of new introductions. In
addition, some effort is currently being made to eradicate selected range-restricted species.
However, only one species that had established and spread on the PEIs, the cat, has been
successfully eradicated from the islands.
CONCLUSION : Given the ongoing threat of introductions, and the impacts of invaders, it is
essential that future invasions to the PEIs are minimised, that the islands’ management policies
deal with all stages of the invasion process and that a better understanding of the risks and
impacts of invasions is obtained.
Description:
This paper was initially delivered at the 43rd Annual Research Symposium on the Management of Biological Invasions in
South Africa, Goudini Spa, Western Cape, South Africa on 18-20 May 2016.