The uneasy coexistence of predators and pathogens
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THE EUROPEAN PHYSICAL JOURNAL E
Regular Article
The uneasy coexistence of predators and pathogens Andreas Eilersena and Kim Sneppenb Niels Bohr Institute, University of Copenhagen, Blegdamsvej 17, 2100 København Ø, Denmark Received 28 February 2020 and Received in final form 19 May 2020 Published online: 2 July 2020 c The Author(s) 2020. This article is published with open access at Springerlink.com Abstract. Disease and predation are both highly important in ecology, and pathogens with multiple host species have turned out to be common. Nonetheless, the interplay between multi-host epidemics and predation has received relatively little attention. Here, we analyse a model of a predator-prey system with disease in both prey and predator populations and determine reasonable parameter values using allometric mass scaling relations. Our analysis focuses on the possibility of extinction events rather than the linear stability of the model equations, and we derive approximate relations for the parameter values at which we expect these events to occur. We find that if the predator is a specialist, epidemics frequently drive the predator species to extinction. If the predator has an additional, immune prey species, predators will usually survive. Coexistence of predator and disease is impossible in the single-prey model. We conclude that for the prey species, carrying a pathogen can be an effective weapon against predators, and that being a generalist is a major advantage for a predator in the event of an epidemic affecting the prey or both species.
Introduction Predation is one of the fundamental modes of interaction among living organisms. Mechanisms similar to predation are found in anything from mammals to bacteria. Another equally important factor is epidemic disease, which is also found on all scales in the ecosphere. In recent years it has become clear that many epidemic pathogens are shared between several species [1], of which some presumably prey on each other. If the predator runs a risk of becoming infected when eating infected prey, it is possible that the prey species will be able to use the pathogen as a weapon against the predator. This could even be a very effective evolutionary strategy, given that prey species are often much more numerous than their predators, leading to a high infection pressure against the predator species [2]. On this basis, we propose the hypothesis that a disease shared between a prey species and its predator will turn out to be a major problem for the predator, and thus perhaps a long-term advantage for the prey. However, if the predator has several prey options, epidemics should pose much less of a threat to it, as it can just feed on an immune prey species in the event of an epidemic.
Supplementary material in the form of a .pdf file available from the Journal web page at https://doi.org/10.1140/epje/i2020-11966-7 a e-mail: [email protected] b e-mail: [email protected]
The dynamics of predator-prey-pathogen interactions in general have received some attention in recen
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