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Keywords:

  • Allele polymorphism;
  • cline;
  • exclusion rule;
  • generalist;
  • habitat;
  • habitat fragmentation;
  • intermediate heterogeneity hypothesis;
  • landscape complementation;
  • spatial heterogeneity;
  • specialist;
  • species diversity

Ecology Letters (2011) 14: 260–266

Abstract

Understanding the conditions for the stable coexistence of different alleles or species is a central topic in theoretical evolution and ecology. Different causes for stable polymorphism or species coexistence have already been identified but they can be grouped into a limited number of general processes. This article is devoted to the presentation and illustration of a new process, which we call ‘habitat boundary polymorphism’, and which relies on two key ingredients: habitat heterogeneity and distance-limited dispersal. Under direct competition and with fixed population densities, we show that this process allows for the equilibrium coexistence of more than n types in a n-habitat environment. Distance-limited dispersal indeed creates local maladaptation at habitat edges, which leaves room for the invasion of more generalist alleles or species. This mechanism provides a generic yet neglected process for the maintenance of polymorphism or species coexistence.