Predators mediate the effects of a fungal pathogen on prey: an experiment with grasshoppers, wolf spiders, and fungal pathogens

Authors

  • ANGELA N. LAWS,

    Corresponding author
    1. Department of Biology, University of Notre Dame, Notre Dame, Indiana, U.S.A.
      Angela N. Laws, Department of Biology, University of Notre Dame, Notre Dame, IN 46556, U.S.A. E-mail: alaws@ksu.edu
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    • Present address: Division of Biology, Kansas State University, Manhattan, KS 66506, U.S.A.

  • THERESE C. FRAUENDORF,

    1. Department of Biology, University of Notre Dame, Notre Dame, Indiana, U.S.A.
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    • *

      These authors contributed equally.

    • Present address: Department of Zoology, Southern Illinois University, Carbondale, IL 62901, U.S.A.

  • JESÚS E. GÓMEZ,

    1. Department of Biology, University of Puerto Rico, Humacao, Puerto Rico, U.S.A.
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    • *

      These authors contributed equally.

  • ISABEL M. ALGAZE

    1. Department of Biology, University of Puerto Rico, Rio Piedras, Puerto Rico, U.S.A.
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    • *

      These authors contributed equally.

    • §

      Present address: Medical Sciences Campus, University of Puerto Rico, San Juan, PR 00936, U.S.A.


Angela N. Laws, Department of Biology, University of Notre Dame, Notre Dame, IN 46556, U.S.A. E-mail: alaws@ksu.edu

Abstract.

1. Prey interact with multiple kinds of enemies such as predators, parasites, and pathogens. Interactions among enemies can alter prey dynamics but they are often studied separately.

2. During the summers of 2005–2006, we conducted a field experiment to examine interactions among grasshoppers, spider predators, and a lethal fungal pathogen of grasshoppers. Grasshopper nymphs were stocked into field enclosures. Predation was manipulated by adding spiders to enclosures on day 1, day 5, or day 10 of the experiment, or no spiders were added. We monitored grasshopper survival and grasshopper mortality from fungal pathogens for 4 weeks.

3. Fungal pathogens were abundant in 2005 but not in 2006, probably because of favourable weather conditions in 2005. When fungal pathogens were abundant, spider presence reduced grasshopper mortality from fungal pathogens, but only when spiders were present early in the experiment (added on day 1 or day 5).

4. The outcome of predator–prey interactions varied between years, probably as a result of differences in pathogen prevalence. In 2005, spider presence reduced the number of deaths from the pathogen, leading to a slight trend of increased grasshopper density. However, in 2006, when pathogens were not an important source of mortality, spider predation was compensatory.

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