Adaptation and the evolution of parasite virulence in a connected world

Geoff Wild*, Andy Gardner, Stuart A. West

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

110 Citations (Scopus)

Abstract

Adaptation is conventionally regarded as occurring at the level of the individual organism, where it functions to maximize the individual's inclusive fitness(1-3). However, it has recently been argued that empirical studies on the evolution of parasite virulence in spatial populations show otherwise(4-7). In particular, it has been claimed that the evolution of lower virulence in response to limited parasite dispersal(8,9) provides proof of Wynne-Edwards's(10) idea of adaptation at the group level. Although previous theoretical work has shown that limited dispersal can favour lower virulence, it has not clarified why, with five different suggestions having been given(6,8,11-15). Here we show that the effect of dispersal on parasite virulence can be understood entirely within the framework of inclusive fitness theory. Limited parasite dispersal favours lower parasite growth rates and, hence, reduced virulence because it (1) decreases the direct benefit of producing offspring(dispersers are worth more than non-dispersers, because they can go to patches with no or fewer parasites), and (2) increases the competition for hosts experienced by both the focal individual ('self-shading') and their relatives ('kin shading'). This demonstrates that reduced virulence can be understood as an individual-level adaptation by the parasite to maximize its inclusive fitness, and clarifies the links with virulence theory more generally(16).

Original languageEnglish
Pages (from-to)983-986
Number of pages4
JournalNature
Volume459
Issue number7249
DOIs
Publication statusPublished - 18 Jun 2009

Keywords

  • INCLUSIVE FITNESS
  • GROUP SELECTION
  • SOCIAL SEMANTICS
  • MODELS
  • COOPERATION
  • BEHAVIOUR
  • ALTRUISM

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