Mechanisms of maintenance of species diversity

P. Chesson

Research output: Contribution to journalArticlepeer-review

4646 Scopus citations


The focus of most ideas on diversity maintenance is species coexistence, which may be stable or unstable. Stable coexistence can be quantified by the long-term rates at which community members recover from low density. Quantification shows that coexistence mechanisms function in two major ways: They may be (a) equalizing because they tend to minimize average fitness differences between species, or (b) stabilizing because they tend to increase negative intraspecific interactions relative to negative interspecific interactions. Stabilizing mechanisms are essential for species coexistence and include traditional mechanisms such as resource partitioning and frequency-dependent predation, as well as mechanisms that depend on fluctuations in population densities and environmental factors in space and time. Equalizing mechanisms contribute to stable coexistence because they reduce large average fitness inequalities which might negate the effects of stabilizing mechanisms. Models of unstable coexitence, in which species diversity slowly decays overtime, have focused almost exclusively on equalizing mechanisms. These models would be more robust if they also included stabilizing mechanisms, which arise in many and varied ways but need not be adequate for full stability of a system. Models of unstable coexistence invite a broader view of diversity maintenance incorporating species turnover.

Original languageEnglish (US)
Pages (from-to)343-366
Number of pages24
JournalAnnual Review of Ecology and Systematics
StatePublished - 2000


  • Coexistence
  • Competition
  • Niche
  • Predation
  • Spatial and temporal variation

ASJC Scopus subject areas

  • Ecology


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