Exotic species richness and native species endemism increase the impact of exotic species on islands |
| |
Authors: | Jessica C. Walsh Oscar Venter Richard A. Fuller Tim M. Blackburn Hugh P. Possingham |
| |
Affiliation: | 1. The Ecology Centre, School of Biological Sciences, The University of Queensland, St Lucia, Qld 4072, Australia;2. CSIRO Climate Adaptation Flagship and CSIRO Ecosystem Sciences, 41 Boggo Road, Dutton Park, Qld 4102, Australia;3. Zoological Society of London, Institute of Zoology, Regent's Park, London NW1?4RY, UK;4. Distinguished Scientist Fellowship Program, King Saud University, PO Box 2455, Riyadh 1145, Saudi Arabia |
| |
Abstract: | Aim Exotic species pose one of the most significant threats to biodiversity, especially on islands. The impacts of exotic species vary in severity among islands, yet little is known about what makes some islands more susceptible than others. Here we determine which characteristics of an island influence how severely exotic species affect its native biota. Location We studied 65 islands and archipelagos from around the world, ranging from latitude 65° N to 54° S. Methods We compiled a global database of 10 island characteristics for 65 islands and determined the relative importance of each characteristic in predicting the impact of exotic species using multivariate modelling and hierarchical partitioning. We defined the impact of exotic species as the number of bird, amphibian and mammal (BAM) species listed by the International Union for Conservation of Nature (IUCN) as threatened by exotics, relative to the total number of BAM species on that island. Results We found that the impact of exotic species is more severe on islands with more exotic species and a greater proportion of native species that are endemic. Unexpectedly, the level of anthropogenic disturbance did not influence an island's susceptibility to the impacts of exotic species. Main conclusions By coupling our results with studies on the introduction and establishment of exotic species, we conclude that colonization pressure, or invasion opportunities, influences all stages of the invasion process. However, species endemism, the other important factor determining the impact of exotic species, is not known to contribute to introduction and establishment success on islands. This demonstrates that different factors correlate with the initial stages of the invasion process and the subsequent impacts of those invaders, highlighting the importance of studying the impacts of exotic species directly. Our study helps identify islands that are at risk of impact by exotics and where investment should focus on preventing further invasions. |
| |
Keywords: | Anthropogenic disturbance colonization pressure endemism exotic species extinction probability islands isolation IUCN Red List |
|
|