title: Human-related processes drive the richness of exotic birds in Europe.
abstract: Both human-related and natural factors can affect the establishment and distribution of exotic species. Understanding the relative role of the different factors has important scientific and applied implications. Here, we examined the relative effect of human-related and natural factors in determining the richness of exotic bird species established across Europe. Using hierarchical partitioning, which controls for covariation among factors, we show that the most important factor is the human-related community-level propagule pressure (the number of exotic species introduced), which is often not included in invasion studies due to the lack of information for this early stage in the invasion process. Another, though less important, factor was the human footprint (an index that includes human population size, land use and infrastructure). Biotic and abiotic factors of the environment were of minor importance in shaping the number of established birds when tested at a European extent using 50 x 50 km2 grid squares. We provide, to our knowledge, the first map of the distribution of exotic bird richness in Europe. The richest hotspot of established exotic birds is located in southeastern England, followed by areas in Belgium and The Netherlands. Community-level propagule pressure remains the major factor shaping the distribution of exotic birds also when tested for the UK separately. Thus, studies examining the patterns of establishment should aim at collecting the crucial and hard-to-find information on community-level propagule pressure or develop reliable surrogates for estimating this factor. Allowing future introductions of exotic birds into Europe should be reconsidered carefully, as the number of introduced species is basically the main factor that determines the number established.
authors.affiliation: The Biodiversity Research Group, Department of Evolution, Systematics and Ecology, The Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
authors.forename: François
authors.initials: F
authors.lastname: Chiron
authors.forename: Susan
authors.initials: S
authors.lastname: Shirley
authors.forename: Salit
authors.initials: S
authors.lastname: Kark
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D044822:Biodiversity; D001717:Birds / Q000502:physiology*; D004777:Environment; D005060:Europe; D005843:Geography; D006801:Humans; D011156:Population Density; D011157:Population Dynamics
references.citation: PLoS Biol. 2008 Feb;6(2):e28
references.pmid: 18254661
references.citation: Ecol Lett. 2007 Jan;10(1):77-94
references.pmid: 17204119
references.citation: Trends Ecol Evol. 2008 May;23(5):237-44
references.pmid: 18367291
references.citation: Proc Natl Acad Sci U S A. 2005 May 17;102(20):7198-202
references.pmid: 15849267
references.citation: Proc Natl Acad Sci U S A. 2004 Dec 21;101(51):17725-30
references.pmid: 15591111
references.citation: Ecology. 2007 Jan;88(1):3-17
references.pmid: 17489447
references.citation: Nature. 2002 Jun 6;417(6889):636-8
references.pmid: 12050662
references.citation: Trends Ecol Evol. 2005 May;20(5):223-8
references.pmid: 16701373
references.citation: Ecology. 2008 Jun;89(6):1541-53
references.pmid: 18589519
references.citation: Proc Natl Acad Sci U S A. 2005 Apr 12;102(15):5460-5
references.pmid: 15784743
references.citation: Nature. 2001 Nov 8;414(6860):195-7
references.pmid: 11700555