Using niche breadth theory to explain generalization in mutualisms

Rebecca T. Batstone, Kelly A. Carscadden, Michelle E. Afkhami, Megan E. Frederickson

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


For a mutualism to remain evolutionarily stable, theory predicts that mutualists should limit their associations to high-quality partners. However, most mutualists either simultaneously or sequentially associate with multiple partners that confer the same type of reward. By viewing mutualisms through the lens of niche breadth evolution, we outline how the environment shapes partner availability and relative quality, and ultimately a focal mutualist's partner breadth. We argue that mutualists that associate with multiple partners may have a selective advantage compared to specialists for many reasons, including sampling, complementarity, and portfolio effects, as well as the possibility that broad partner breadth increases breadth along other niche axes. Furthermore, selection for narrow partner breadth is unlikely to be strong when the environment erodes variation in partner quality, reduces the costs of interacting with low-quality partners, spatially structures partner communities, or decreases the strength of mutualism. Thus, we should not be surprised that most mutualists have broad partner breadth, even if it allows for ineffective partners to persist.

Original languageEnglish (US)
Pages (from-to)1039-1050
Number of pages12
Issue number5
StatePublished - May 2018


  • cheaters
  • generalization
  • mutualism
  • niche breadth
  • specialization
  • symbiosis

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics


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