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A global picture of biological invasion threat on islands


Biological invasions are among the main drivers of biodiversity losses. As threats from biological invasions increase, one of the most urgent tasks is to identify areas of high vulnerability. However, the lack of comprehensive information on the impacts of invasive alien species (IAS) is a problem especially on islands, where most of the recorded extinctions associated with IAS have occurred. Here we provide a global, network-oriented analysis of IAS on islands. Using network analysis, we structured 27,081 islands and 437 threatened vertebrates into 21 clusters, based on their profiles in term of invasiveness and shared vulnerabilities. These islands are mainly located in the Southern Hemisphere and many are in biodiversity hotspots. Some of the islands share similar characteristics regarding their connectivity that could be useful for understanding their response to invasive species. The major invaders found in these clusters of islands are feral cats, feral dogs, pigs and rats. Our analyses reveal those IAS that systematically act alone or in combination, and the pattern of shared IAS among threatened species, providing new information to implement effective eradication strategies. Combined with further local, contextual information this can contribute to global strategies to deal with IAS.

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C.B. was supported by an Axa Fellowship. We thank S. Pagad; C. Leclerc and J. Jeschke for their comments on an earlier version of the manuscript; F. Courchamp for fruitful discussions.

Author information

C.B. and J.-F.R. conceived and designed the study with contributions by G.M.M. J.-F.R. and C.B. carried out the analyses, B.L. provided the initial version of the computing code. C.B. and J.-F.R. wrote the first draft of the manuscript and all authors substantially contributed to interpreting and writing the manuscript.

Competing interests

The authors declare no competing financial interests.

Correspondence to Céline Bellard.

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Fig. 1: Bipartite IAS-threatened species and islands network.
Fig. 2: Interaction network betweeen IAS and threatened species and number of species that could benefit from removal of IAS.
Fig. 3: Examples of network characteristics.