Abstract
Ecological and epidemiological processes and interactions influence each other, positively and negatively, directly and indirectly. The invasion potential of pathogens is influenced by the ecosystem context of their host species’ populations. This extends to the capacity of (multiple) host species to maintain their (common) pathogen and the way pathogen dynamics are influenced by changes in ecosystem composition. This paper exemplifies these interactions and consequences in a study of red and grey squirrel dynamics in the UK. Differences and changes in background habitat and trophic levels above and below the squirrel species lead to different dynamic behaviour in many subtle ways. The range of outcomes of the different interactions shows that one has to be careful when drawing conclusions about the mechanisms and processes involved in explaining observed phenomena concerning pathogens in their natural environment. The dynamic behaviour also shows that planning interventions, for example for conservation purposes, benefits from understanding the complexity of interactions beyond the particular pathogen and its threatened host species.
Highlights
The dynamics of pathogens in natural systems are shaped by their host species but by the entire ecosystem of which they are part [1,2,3]
The results illustrate the richness of analysis that can be performed and insights that can be gained when combining even rudimentary ecology and epidemiology in a toy ecosystem, and show how essential it is to recognize the indirect roles of non-host species at various trophic levels
We have presented and analysed a model for the interaction of two herbivore species competing for resources, in the presence of a pathogen infecting both of them, and in response to changes in the trophic levels below and above
Summary
The dynamics of pathogens in natural systems are shaped by their host species but by the entire ecosystem of which they are part [1,2,3]. We have previously defined a general and relatively simple model ecoepidemiological system that incorporates competition within and between any number of host and non-host species, including consumer–resource relationships [7,8,9] Using this system, we have shown that even subtle effects on interaction strengths between ecosystem species influence the pathogen dynamics among its hosts. Something similar holds for whether there is a dilution or amplification effect for a pathogen It seems that taking a fuller view of the ecosystem context is needed to be able to understand observed patterns of pathogen dynamics and the roles of host species in those dynamics. We study a host–pathogen system that has the minimal requirements for a meaningful analysis: a single pathogen, multiple host species, non-host species, different trophic levels, competition and consumer–resource interaction, and different observed dynamics under different circumstances. The results illustrate the richness of analysis that can be performed and insights that can be gained when combining even rudimentary ecology and epidemiology in a toy ecosystem, and show how essential it is to recognize the indirect roles of non-host species at various trophic levels
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