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TROPHIC POLYMORPHISM AND BEHAVIORAL DIFFERENCES DECREASE INTRASPECIFIC COMPETITION IN A CICHLID, HERICHTHYS MINCKLEYI
Author(s) -
Swanson Brook O.,
Gibb Alice C.,
Marks Jane C.,
Hendrickson Dean A.
Publication year - 2003
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.1890/02-0353
Subject(s) - intraspecific competition , biology , cichlid , ecology , competition (biology) , trophic level , population , interspecific competition , zoology , fish <actinopterygii> , fishery , demography , sociology
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. Corresponding Editor: S. Nylin.