Remoteness promotes biological invasions on islands worldwide

Dietmar Moser, Bernd Lenzner, Patrick Weigelt, Wayne Dawson, Holger Kreft, Jan Pergl, Petr Pyšek, Mark van Kleunen, Marten Winter, César Capinha, Phillip Cassey, Stefan Dullinger, Evan P. Economo, Pablo García-Díaz, Benoit Guénard, Florian Hofhansl, Thomas Mang, Hanno Seebens, and Franz Essl
PNAS September 11, 2018 115 (37) 9270-9275; published ahead of print August 29, 2018 https://doi.org/10.1073/pnas.1804179115

  1. Edited by Daniel S. Simberloff, The University of Tennessee, Knoxville, TN, and approved August 2, 2018 (received for review March 9, 2018)

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Significance

Islands are hotspots of alien species invasions, and their distinct biodiversity is particularly vulnerable to invading species. While isolation has shaped natural colonization of islands for millions of years, globalization in trade and transport has led to a breakdown of biogeographical barriers and subsequent colonization of islands by alien species. Using a large dataset of 257 subtropical and tropical islands, we show that alien richness increases with increasing isolation of islands. This pattern is consistent for plants, ants, mammals, and reptiles, and it cannot simply be explained by island economics and trade alone. Geographical isolation does not protect islands from alien species, and island species richness may reach a new dynamic equilibrium at some point, likely at the expense of many endemic species.

Abstract

One of the best-known general patterns in island biogeography is the species–isolation relationship (SIR), a decrease in the number of native species with increasing island isolation that is linked to lower rates of natural dispersal and colonization on remote oceanic islands. However, during recent centuries, the anthropogenic introduction of alien species has increasingly gained importance and altered the composition and richness of island species pools. We analyzed a large dataset for alien and native plants, ants, reptiles, mammals, and birds on 257 (sub) tropical islands, and showed that, except for birds, the number of naturalized alien species increases with isolation for all taxa, a pattern that is opposite to the negative SIR of native species. We argue that the reversal of the SIR for alien species is driven by an increase in island invasibility due to reduced diversity and increased ecological naiveté of native biota on the more remote islands.

Footnotes

  • ↵1D.M. and B.L. contributed equally to this work.

  • ↵2To whom correspondence should be addressed. Email: bernd.lenzner{at}univie.ac.at.

  • Author contributions: D.M. and B.L. designed research; D.M. and B.L. performed research; P.W., W.D., H.K., J.P., P.P., M.v.K., M.W., C.C., P.C., S.D., E.P.E., P.G.-D., B.G., H.S., and F.E. contributed data for the different taxonomic groups; D.M., B.L., F.H., and T.M. analyzed data; and D.M., B.L., P.W., W.D., H.K., J.P., P.P., M.v.K., M.W., C.C., P.C., S.D., E.P.E., P.G.-D., B.G., F.H., T.M., H.S., and F.E. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

  • This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1804179115/-/DCSupplemental.

Published under the PNAS license.

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Remoteness promotes biological invasions on islands worldwide
Dietmar Moser, Bernd Lenzner, Patrick Weigelt, Wayne Dawson, Holger Kreft, Jan Pergl, Petr Pyšek, Mark van Kleunen, Marten Winter, César Capinha, Phillip Cassey, Stefan Dullinger, Evan P. Economo, Pablo García-Díaz, Benoit Guénard, Florian Hofhansl, Thomas Mang, Hanno Seebens, Franz Essl
Proceedings of the National Academy of Sciences Sep 2018, 115 (37) 9270-9275; DOI: 10.1073/pnas.1804179115
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