Predator richness has no effect in a diverse marine food web

Authors

  • Mary I. O’Connor,

    Corresponding author
    1. Curriculum in Ecology, The University of North Carolina, Chapel Hill, NC 27599-3275, USA
    2. Department of Marine Sciences, The University of North Carolina, Chapel Hill, NC 27599-3300, USA
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  • John F. Bruno

    1. Department of Marine Sciences, The University of North Carolina, Chapel Hill, NC 27599-3300, USA
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*Correspondence author. Mary I. O’Connor, National Center for Ecological Analysis and Synthesis, 735 State Street, Suite 300, Santa Barbara, CA 93101, USA. E-mail: oconnor@nceas.ucsb.edu

Summary

  • 1In many ecosystems, predator abundance, composition and diversity vary naturally among seasons and habitats. In addition, predator assemblages are changing due to overharvesting, habitat destruction and species invasions.
  • 2Predator species composition and richness can influence prey community structure and these effects can cascade to influence plant abundance and composition.
  • 3To test the effects of predator presence, composition and species richness on prey abundance, species richness and composition, we conducted three experiments in a subtidal marine food web. Experimental food webs were drawn from species pools of 5–7 predator species, 19–52 prey species, benthic micro-algae and 5 macro-algae.
  • 4Predators reduced prey abundance in the mesocosm experiment, but this effect was diminished or absent in field experiments. Predator species differed in their effects on prey, but we found no effect of predator richness (via complementarity or selection) on any aspect of prey community structure.
  • 5The absence of a predator richness effect could be due to several factors including potentially opposing effects of individual predator species, intraguild predation, or greater importance of colonization relative to competition in structuring prey assemblages. Although predators can have strong top-down effects in this system, selection or resource-use complementarity among predators do not affect prey community structure.

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