title: The Global Distribution and Drivers of Alien Bird Species Richness.
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 distribution 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 economic activity. We find that, globally, alien bird species richness is currently highest at midlatitudes 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 positively associated. Our results demonstrate that colonisation pressure is key to understanding 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.
authors.affiliation: Centre for Biodiversity and Environment Research, Department of Genetics, Evolution and Environment, University College London, London, United Kingdom.|Institute of Zoology, Zoological Society of London, Regent's Park, London, United Kingdom.
authors.forename: Ellie E
authors.initials: EE
authors.lastname: Dyer
authors.affiliation: Centre for Conservation Science and Technology, and School of Biological Sciences, University of Adelaide, Adelaide, South Australia, Australia.
authors.forename: Phillip
authors.initials: P
authors.lastname: Cassey
authors.affiliation: Centre for Biodiversity and Environment Research, Department of Genetics, Evolution and Environment, University College London, London, United Kingdom.
authors.forename: David W
authors.initials: DW
authors.lastname: Redding
authors.affiliation: Centre for Biodiversity and Environment Research, Department of Genetics, Evolution and Environment, University College London, London, United Kingdom.
authors.forename: Ben
authors.initials: B
authors.lastname: Collen
authors.affiliation: Institute of Zoology, Zoological Society of London, Regent's Park, London, United Kingdom.|Department of Zoology, University of Cambridge, Cambridge, United Kingdom.
authors.forename: Victoria
authors.initials: V
authors.lastname: Franks
authors.affiliation: Environment and Sustainability Institute, University of Exeter, Penryn, Cornwall, United Kingdom.
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Gaston
authors.affiliation: Centre for Biodiversity and Environment Research, Department of Genetics, Evolution and Environment, University College London, London, United Kingdom.|Institute of Zoology, Zoological Society of London, Regent's Park, London, United Kingdom.
authors.forename: Kate E
authors.initials: KE
authors.lastname: Jones
authors.affiliation: The Biodiversity Research Group, School of Biological Sciences, ARC Centre of Excellence for Environmental Decisions and NESP Threatened Species hub, The University of Queensland, Brisbane, Queensland, Australia.
authors.forename: Salit
authors.initials: S
authors.lastname: Kark
authors.affiliation: Division of Biology, Imperial College London, Silwood Park, Ascot, Berkshire, United Kingdom.
authors.forename: C David L
authors.initials: CD
authors.lastname: Orme
authors.affiliation: Centre for Biodiversity and Environment Research, Department of Genetics, Evolution and Environment, University College London, London, United Kingdom.|Institute of Zoology, Zoological Society of London, Regent's Park, London, United Kingdom.|Distinguished Scientist Fellowship Program, King Saud University, Riyadh, Saudi Arabia.|Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Matieland, South Africa.
authors.forename: Tim M
authors.initials: TM
authors.lastname: Blackburn
mesh_terms: D000818:Animals; D044822:Biodiversity; D001717:Birds / Q000502:physiology*; D059066:Gross Domestic Product; D038622:Internationality; D058865:Introduced Species; D013045:Species Specificity; D013997:Time Factors