Population dynamics of obligate cooperators

F. Courchamp, B. Grenfell, T. Clutton-Brock

Research output: Contribution to journalArticle

110 Scopus citations

Abstract

Obligate cooperative breeding species demonstrate a high rate of group extinction, which may he due to the existence of a critical number of helpers below which the group cannot subsist. Through a simple model, we study the population dynamics of obligate cooperative breeding species, taking into account the existence of a lower threshold below which the instantaneous growth rate becomes negative. The model successively incorporates (i) a distinction between species that need helpers for reproduction, survival or both, (ii) the existence of a migration rate accounting for dispersal, and (iii) stochastic mortality to simulate the effects of random catastrophic events. Our results suggest that the need for a minimum number of helpers increases the risk of extinction for obligate cooperative breeding species. The constraint imposed by this threshold is higher when helpers are needed for reproduction only or for both reproduction and survival. By driving them below this lower threshold, stochastic mortality of lower amplitude and/or lower frequency than for non-cooperative breeders may be sufficient to cause the extinction of obligate cooperative breeding groups. Migration may have a buffering effect only for groups where immigration is higher than emigration; otherwise (when immigrants from nearby groups are not available) it lowers the difference between actual group size and critical threshold, thereby constituting a higher constraint.

Original languageEnglish (US)
Pages (from-to)557-563
Number of pages7
JournalProceedings of the Royal Society B: Biological Sciences
Volume266
Issue number1419
DOIs
StatePublished - Mar 22 1999

All Science Journal Classification (ASJC) codes

  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)
  • Environmental Science(all)
  • Agricultural and Biological Sciences(all)

Keywords

  • Allee effect
  • Group extinction
  • Inverse density dependence
  • Mathematical model
  • Obligate cooperative breeding species
  • Population dynamics

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