Allee Effect from Parasite Spill-Back

• Published in: The American Naturalist
• Main Authors: Krkosek, Martin, Ashander, Jaime, Frazer, L. Neil, Lewis, Mark A.
• Other Authors: Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada, Salmon Coast Field Station, Simoom Sound, BC, Canada, Department of Zoology, University of Otago, Dunedin, New Zealand, Centre for Mathematical Biology, University of Alberta, Edmonton, AB, Canada, Department of Environmental Science and Policy and Center for Population Biology, University of California, Davis, CA, United States, Department of Geology and Geophysics, University of Hawaii at Manoa, Honolulu, HI, United States, Department of Mathematical and Statistical Sciences, Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: University of Chicago Press 2013
• Subjects: disease; conservation; depensation; transmission; fisheries; salmon; Canada; Pacific; Oncorhynchus gorbuscha; Pink salmon
• Online Access: http://hdl.handle.net/10754/671342; https://doi.org/10.1086/673238

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. 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 ...