Coexistence of annual plants: Generalist seed predation weakens the storage effect

Jessica J. Kuang, Peter Chesson

Research output: Contribution to journalArticle

38 Scopus citations

Abstract

We investigate the effect of seed predation on the coexistence of competing annual plants. We demonstrate a role for predation that is opposite to the conventional wisdom that predation promotes coexistence by reducing the intensity of competition. In the common situation where competitive coexistence involves intraspecific competition exceeding interspecific competition, predation can undermine coexistence by reducing the overall magnitude of competition, replacing competition with "apparent competition" in a way that does not lead to differential intraspecific and interspecific effects. We demonstrate this outcome in the case where coexistence occurs by "the storage effect" in a variable environment. The storage effect arises when the environment interacts with competition to create opportunities for species to increase from low density. Critical to the storage effect is positive covariance between the response of population growth to the environment and its response to competition, when a species is at high density. This outcome prevents species at high density from taking advantage of favorable environmental conditions. A species at low density has lower covariance and can take advantage of favorable environmental conditions, giving it an advantage over a high-density species, fostering its recovery from low density. Hence, species coexistence is promoted. Here we find that density-dependent predation lowers population densities, and so weakens competition, replacing competition with apparent competition, which does not covary with the environment. As a consequence, covariance between environment and competition is weakened, reducing the advantage to a species at low density. The species still strongly interact through the combination of competition and apparent competition, but the reduced low-density advantage reduces their ability to coexist. Although this result is demonstrated specifically for the storage effect with a focus on annual plant communities, the principles involved are general ones.

Original languageEnglish (US)
Pages (from-to)170-182
Number of pages13
JournalEcology
Volume90
Issue number1
DOIs
StatePublished - Jan 1 2009

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Keywords

  • Annual plant community
  • Apparent competition
  • Competition
  • Seed predation
  • Species coexistence
  • Storage effect
  • Temporal environmental variation

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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