INTRAGUILD PREDATION DRIVES EVOLUTIONARY NICHE SHIFT IN THREESPINE STICKLEBACK

Authors

  • Travis Ingram,

    1. Department of Zoology and Biodiversity Research Centre, University of British Columbia, 2370–6270 University Blvd., Vancouver, British Columbia V6T 1Z4, Canada
    2. E-mail: ingram@fas.harvard.edu
    Search for more papers by this author
    • Current address: Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford St., Cambridge, Massachusetts 02138

  • Richard Svanbäck,

    1. Department of Zoology and Biodiversity Research Centre, University of British Columbia, 2370–6270 University Blvd., Vancouver, British Columbia V6T 1Z4, Canada
    Search for more papers by this author
    • Current address: Department of Ecology and Genetics/Limnology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, Uppsala SE-752 36, Sweden

  • Nathan J. B. Kraft,

    1. Biodiversity Research Centre, University of British Columbia, 2370–6270 University Blvd., Vancouver, British Columbia V6T 1Z4, Canada
    Search for more papers by this author
  • Pavel Kratina,

    1. Department of Zoology and Biodiversity Research Centre, University of British Columbia, 2370–6270 University Blvd., Vancouver, British Columbia V6T 1Z4, Canada
    Search for more papers by this author
  • Laura Southcott,

    1. Department of Zoology and Biodiversity Research Centre, University of British Columbia, 2370–6270 University Blvd., Vancouver, British Columbia V6T 1Z4, Canada
    Search for more papers by this author
  • Dolph Schluter

    1. Department of Zoology and Biodiversity Research Centre, University of British Columbia, 2370–6270 University Blvd., Vancouver, British Columbia V6T 1Z4, Canada
    Search for more papers by this author

Abstract

Intraguild predation—competition and predation by the same antagonist—is widespread, but its evolutionary consequences are unknown. Intraguild prey may evolve antipredator defenses, superior competitive ability on shared resources, or the ability to use an alternative resource, any of which may alter the structure of the food web. We tested for evolutionary responses by threespine stickleback to a benthic intraguild predator, prickly sculpin. We used a comparative morphometric analysis to show that stickleback sympatric with sculpin are more armored and have more limnetic-like body shapes than allopatric stickleback. To test the ecological implications of this shift, we conducted a mesocosm experiment that varied sculpin presence and stickleback population of origin (from one sympatric and one allopatric lake). Predation by sculpin greatly increased the mortality of allopatric stickleback. In contrast, sculpin presence did not affect the mortality of sympatric stickleback, although they did have lower growth rates suggesting increased nonpredatory effects of sculpin. Consistent with their morphology, sympatric stickleback included more pelagic prey in their diets, leading to depletion of zooplankton in the mesocosms. These findings suggest that intraguild prey evolution has altered food web structure by reducing both predation by the intraguild predator and diet overlap between species.

Ancillary