Coevolution between mutualists and parasites in symbiotic communities may lead to the evolution of lower virulence

Paul G. Nelson, Georgiana May

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Most eukaryotes harbor a diverse community of parasitic, mutualistic, and commensal microbial symbionts. Although the diversity of these microbial symbiotic communities has recently drawn considerable attention, theory regarding the evolution of interactions among symbionts and with the host is still in its nascent stages. Here we evaluate the role of interactions among coinfecting symbionts in the evolution of symbiont virulence toward the host. To do so, we place the virulence-transmission trade-off into a community context and model the evolution of symbiont trophic modes along the continuum from parasitism (virulence) to mutualism (negative virulence). We establish a framework for studying multiple infections of a host by the same symbiont species and coinfection bymultiple species, using a concept of shared costs, wherein the negative consequences of virulence (or harm) toward the host are shared among symbionts. Our results show that mutualism can be maintained under infection bymultiple symbionts when shared costs are sufficiently low, while greater virulence and parasitism toward the host are more likely when shared costs are high. Last, for coinfection by more than one species, we show that if the presence of a mutualist ameliorates some of the costs of pathogen virulence, then the symbiotic community may more often evolve to a more commensal state and maintain mutualisms.

Original languageEnglish (US)
Pages (from-to)803-817
Number of pages15
JournalAmerican Naturalist
Issue number6
StatePublished - Dec 2017

Bibliographical note

Publisher Copyright:
© 2017 by The University of Chicago. All rights reserved.


  • Coevolution
  • Mutualism
  • Parasitism
  • Symbiosis
  • Trade-offs
  • Virulence


Dive into the research topics of 'Coevolution between mutualists and parasites in symbiotic communities may lead to the evolution of lower virulence'. Together they form a unique fingerprint.

Cite this