The Global Distribution and Drivers of Alien Bird Species Richness

Dyer, Ellie E.; Cassey, Phillip; Redding, David W.; Collen, Ben; Franks, Victoria; Gaston, Kevin J.; Jones, Kate E.; Kark, Salit; Orme, C.David L.; Blackburn, Tim M.

Abstract

Alien species are a major component of human-induced environmental change. Variation in
the numbers of alien species found in different areas is likely to depend on a combination of
anthropogenic and environmental factors, with anthropogenic factors affecting the number
of species introduced to new locations, and when, and environmental factors influencing
how many species are able to persist there. However, global spatial and temporal variation
in the drivers of alien introduction and species richness remain poorly understood. Here, we
analyse an extensive new database of alien birds to explore what determines the global dis-
tribution of alien species richness for an entire taxonomic class. We demonstrate that the
locations of origin and introduction of alien birds, and their identities, were initially driven
largely by European (mainly British) colonialism. However, recent introductions are a wider
phenomenon, involving more species and countries, and driven in part by increasing eco-
nomic activity. We find that, globally, alien bird species richness is currently highest at mid-
latitudes and is strongly determined by anthropogenic effects, most notably the number of
species introduced (i.e., “colonisation pressure”). Nevertheless, environmental drivers are
also important, with native and alien species richness being strongly and consistently posi-
tively associated. Our results demonstrate that colonisation pressure is key to understand-
ing alien species richness, show that areas of high native species richness are not resistant
to colonisation by alien species at the global scale, and emphasise the likely ongoing threats
to global environments from introductions of species.

• Journal Article Type: Article
• Acceptance Date: Dec 9, 2016
• Publication Date: Jan 12, 2017
• Deposit Date: Sep 26, 2024
• Publicly Available Date: Sep 27, 2024
• Journal: PLOS Biology
• Print ISSN: 1544-9173
• Electronic ISSN: 1545-7885
• Publisher: Public Library of Science
• Peer Reviewed: Peer Reviewed
• DOI: https://doi.org/10.1371/journal.pbio.2000942