Realized vs apparent reduction in enemies of the European starling

Release from parasites, pathogens or predators (i.e. enemies) is a widely cited 'rule of thumb' to explain the proliferation of nonindigenous species in their introduced regions (i.e. the 'enemy release hypothesis', or ERH). Indeed, profound effects of some parasites and predator...

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Bibliographic Details
Published in:Biological invasions 2005-07, Vol.7 (4), p.723-732
Main Authors: Colautti, R.I, Muirhead, J.R, Biswas, R.N, MacIsaac, H.J
Format: Article
Language:English
Subjects:
enemy release hypothesis
Eurasia
geographical variation
helminths
host-parasite relationships
Introduced species
invasive species
natural enemies
Nonnative species
Parasites
Predators
species diversity
Species richness
Sturnus vulgaris
wild birds
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Summary:Release from parasites, pathogens or predators (i.e. enemies) is a widely cited 'rule of thumb' to explain the proliferation of nonindigenous species in their introduced regions (i.e. the 'enemy release hypothesis', or ERH). Indeed, profound effects of some parasites and predators on host populations are well documented. However, some support for the ERH comes from studies that find a reduction in the species richness of enemies in the introduced range, relative to the native range, of particular hosts. For example, data on helminth parasites of the European starling in both its native Eurasia and in North America support a reduction of parasites in the latter. However, North American 'founder' starlings were likely not chosen randomly from across Eurasia. This could result in an overestimation of enemy release since enemies affect their hosts on a population level. We control for the effects of subsampling colonists and find, contrary to previous reports, no evidence that introduced populations of starlings experienced a reduction in the species richness of helminth parasites after colonization of North America. These results highlight the importance of choosing appropriate contrast groups in biogeographical analyses of biological invasions to minimize the confounding effects of 'propagule biases'.[PUBLICATION ABSTRACT]
ISSN:1387-3547
1573-1464
DOI:10.1007/s10530-004-0998-7