, Volume 169, Issue 4, pp 1095–1103 | Cite as

Multiple defender effects: synergistic coral defense by mutualist crustaceans

  • C. Seabird  McKeon
  • Adrian C. Stier
  • Shelby E. McIlroy
  • Benjamin M. Bolker
Community ecology - Original research


The majority of our understanding of mutualisms comes from studies of pairwise interactions. However, many hosts support mutualist guilds, and interactions among mutualists make the prediction of aggregate effects difficult. Here, we apply a factorial experiment to interactions of ‘guard’ crustaceans that defend their coral host from seastar predators. Predation was reduced by the presence of mutualists (15% reduction in predation frequency and 45% in volume of coral consumed). The frequency of attacks with both mutualists was lower than with a single species, but it did not differ significantly from the expected frequency of independent effects. In contrast, the combined defensive efficacy of both mutualist species reduced the volume of coral tissue lost by 73%, significantly more than the 38% reduction expected from independent defensive efforts, suggesting the existence of a cooperative synergy in defensive behaviors of ‘guard’ crustaceans. These emergent ‘multiple defender effects’ are statistically and ecologically analogous to the emergent concept of ‘multiple predator effects’ known from the predation literature.


Alpheus Coral reefs Exosymbiont Multiple predator effects Trapezia 

Supplementary material

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Supplementary material 1 (PDF 297 kb)
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Supplementary material 2 (RNW 18 kb)
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Supplementary material 3 (RNW 23 kb)


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Copyright information

© Springer-Verlag 2012

Authors and Affiliations

  • C. Seabird  McKeon
    • 1
  • Adrian C. Stier
    • 2
  • Shelby E. McIlroy
    • 3
  • Benjamin M. Bolker
    • 2
    • 4
  1. 1.Smithsonian Marine StationFort PierceUSA
  2. 2.Department of BiologyUniversity of FloridaGainesvilleUSA
  3. 3.Department of GeologyUniversity at BuffaloBuffaloUSA
  4. 4.Departments of Mathematics and Statistics and BiologyMcMaster UniversityHamiltonCanada

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