Epidemiological, Evolutionary, and Coevolutionary Implications of Context-Dependent Parasitism

Pedro Vale, Alastair J. Wilson, Alex Best, Mike Boots, Tom J. Little

Research output: Contribution to journalArticlepeer-review

Abstract

Victims of infection are expected to suffer increasingly as parasite population growth increases. Yet, under some conditions, faster-growing parasites do not appear to cause more damage, and infections can be quite tolerable. We studied these conditions by assessing how the relationship between parasite population growth and host health is sensitive to environmental variation. In experimental infections of the crustacean Daphnia magna and its bacterial parasite Pasteuria ramosa, we show how easily an interaction can shift from a severe interaction, that is, when host fitness declines substantially with each unit of parasite growth, to a tolerable relationship by changing only simple environmental variables: temperature and food availability. We explored the evolutionary and epidemiological implications of such a shift by modeling pathogen evolution and disease spread under different levels of infection severity and found that environmental shifts that promote tolerance ultimately result in populations harboring more parasitized individuals. We also find that the opportunity for selection, as indicated by the variance around traits, varied considerably with the environmental treatment. Thus, our results suggest two mechanisms that could underlie coevolutionary hotspots and coldspots: spatial variation in tolerance and spatial variation in the opportunity for selection.

Original languageEnglish
Pages (from-to)510-521
Number of pages12
JournalThe American Naturalist
Volume177
Issue number4
DOIs
Publication statusPublished - Apr 2011

Keywords

  • coevolution
  • context dependent
  • virulence
  • parasitism
  • tolerance
  • BY-ENVIRONMENT INTERACTIONS
  • HOST-PARASITE
  • GENETIC-VARIATION
  • MICROPARASITE SYSTEM
  • VIRULENCE
  • TRANSMISSION
  • RESISTANCE
  • TOLERANCE
  • SELECTION
  • MAINTENANCE

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