Herbivore physiological response to predation risk and implications for ecosystem nutrient dynamics

Dror Hawlena, Oswald J. Schmitz

Research output: Contribution to journalArticlepeer-review

240 Scopus citations

Abstract

The process of nutrient transfer through an ecosystem is an important determinant of production, food-chain length, and species diversity. The general viewis that the rate and efficiency ofnutrient transfer up the food chain is constrained by herbivore-specific capacity to secure N-rich compounds for survival and production. Using feeding trials with artificial food, we show, however, that physiological stress-response of grasshopper herbivores to spider predationrisk alters the nature of the nutrient constraint. Grasshoppers facing predation risk had higher metabolic rates than control grasshoppers. Elevated metabolism accordingly increased requirements for dietary digestible carbohydrate-C to fuel-heightened energy demands. Moreover, digestible carbohydrate-C comprises a small fraction of total plant tissue-C content, so nutrient transfer between plants and herbivores accordingly becomes more constrained by digestible plant C than by total plant C:N. This shift in herbivore diet to meet the altered nutrient requirement increased herbivore body C:N content, the C:N content of the plant community from which grasshoppers select their diet, and grasshopper fecal C:N content. Chronic predation risk thus alters the quality of animal and plant tissue that eventually enters the detrital pool to become decomposed. Our results demonstrate that herbivore physiology causes C:N requirements and nutrient intake to become flexible, thereby providing a mechanism to explain context dependence in the nature of trophic control over nutrient transfer in ecosystems.

Original languageAmerican English
Pages (from-to)15503-15507
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume107
Issue number35
DOIs
StatePublished - 31 Aug 2010
Externally publishedYes

Keywords

  • Ecological stoichiometry
  • Metabolism
  • Nutrient balance
  • Physiological stress
  • Predator-prey interaction

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