Allee Effect from Parasite Spill-Back

Martin Krkosek, Jaime Ashander, L. Neil Frazer, Mark A. Lewis

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


The exchange of native pathogens between wild and domesticated animals can lead to novel disease threats to wildlife. However, the dynamics of wild host-parasite systems exposed to a reservoir of domesticated hosts are not well understood. A simple mathematical model reveals that the spill-back of native parasites from domestic to wild hosts may cause a demographic Allee effect in the wild host population. A second model is tailored to the particulars of pink salmon (Oncorhynchus gorbuscha) and salmon lice (Lepeophtheirus salmonis), for which parasite spill-back is a conservation and fishery concern. In both models, parasite spill-back weakens the coupling of parasite and wild host abundance-particularly at low host abundance-causing parasites per host to increase as a wild host population declines. These findings show that parasites shared across host populations have effects analogous to those of generalist predators and can similarly cause an unstable equilibrium in a focal host population that separates persistence and extirpation. Allee effects in wildlife arising from parasite spill-back are likely to be most pronounced in systems where the magnitude of transmission from domestic to wild host populations is high because of high parasite abundance in domestic hosts, prolonged sympatry of domestic and wild hosts, a high transmission coefficient for parasites, long-lived parasite larvae, and proximity of domesticated populations to wildlife migration corridors. © 2013 by The University of Chicago.
Original languageEnglish (US)
Pages (from-to)640-652
Number of pages13
JournalAmerican Naturalist
Issue number5
StatePublished - 2013
Externally publishedYes

Bibliographical note

KAUST Repository Item: Exported on 2021-09-21
Acknowledged KAUST grant number(s): KUK-C1-013-04
Acknowledgements: We thank the reviewers, whose comments improved the work. This work was supported by funding from the University of Otago (M. K.), the Natural Sciences and Engineering Research Council of Canada (M. K. and M. A. L.), the Pacific Institute of Mathematical Sciences International Graduate Training Centre in Mathematical Biology (J.A.), a REACH (Responding to Rapid Environmental Change) Integrative Graduate Education and Research Traineeship (IGERT; J.A.), and a Canada Research Chair (M. A. L.). M. A. L. also gratefully acknowledges the Oxford Centre for Collaborative Applied Mathematics, supported in part by Award KUK-C1-013-04, made by King Abdullah University of Science and Technology.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.

ASJC Scopus subject areas

  • General Medicine


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