Population dynamics and mutualism: Functional responses of benefits and costs

J. Nathaniel Holland, Donald L. DeAngelis, Judith L. Bronstein

Research output: Contribution to journalArticlepeer-review

213 Scopus citations


We develop an approach for studying population dynamics resulting from mutualism by employing functional responses based on density-dependent benefits and costs. These functional responses express how the population growth rate of a mutualist is modified by the density of its partner. We present several possible dependencies of gross benefits and costs, and hence net effects, to a mutualist as functions of the density of its partner. Net effects to mutualists are likely a monotonically saturating or unimodal function of the density of their partner. We show that fundamental differences in the growth, limitation, and dynamics of a population can occur when net effects to that population change linearly, unimodally, or in a saturating fashion. We use the mutualism between senita cactus and its pollinating seed-eating moth as an example to show the influence of different benefit and cost functional responses on population dynamics and stability of mutualisms. We investigated two mechanisms that may alter this mutualism's functional responses: distribution of eggs among flowers and fruit abortion. Differences in how benefits and costs vary with density can alter the stability of this mutualism. In particular, fruit abortion may allow for a stable equilibrium where none could otherwise exist.

Original languageEnglish (US)
Pages (from-to)231-244
Number of pages14
JournalAmerican Naturalist
Issue number3
StatePublished - 2002


  • Benefits and costs
  • Density dependence
  • Functional response
  • Mutuatism
  • Population dynamics
  • Stability

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics


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