Trophic polymorphism and behavioral differences decrease intraspecific competition in a cichlid, Herichthys minckleyi

Brook O. Swanson, Alice C. Gibb, Jane C. Marks, Dean A. Hendrickson

Research output: Contribution to journalArticle

77 Scopus citations


Resource polymorphisms, or morphological variations related to resource use, are common in fishes and are thought to be a possible step in speciation. This study experimentally tests the hypothesis that fitness (as estimated by growth rates) is increased by the presence of multiple trophic morphotypes (or morphs) within a population. Cage experiments were used to quantify the intraspecific competitive interactions between morphs of the polymorphic cichlid Herichthys minckleyi in Cuatro Ciénegas, Mexico. Results suggest that competition is reduced between morphs in mixed-morph treatments relative to equal-density single-morph treatments. Field studies revealed that the morphs feed in different microhabitats and use different feeding behaviors within these microhabitats. These results suggest that the polymorphism is maintained in the population because it decreases competition between the morphs, and that differences in feeding behavior facilitate resource partitioning.

Original languageEnglish (US)
Pages (from-to)1441-1446
Number of pages6
Issue number6
StatePublished - Jun 2003



  • Cichlid
  • Competition
  • Ecological speciation
  • Feeding behavior
  • Herichthys minckleyi
  • Intraspecific variation
  • Polymorphism
  • Resource partitioning

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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