Table of Contents
International Journal of Evolutionary Biology
Volume 2011, Article ID 689254, 9 pages
Review Article

Male-Male Competition as a Force in Evolutionary Diversification: Evidence in Haplochromine Cichlid Fish

1Behavioural Biology Research Group, University of Groningen, P.O. Box 14, 9750 AA Haren, The Netherlands
2Section of Integrative Biology, The University of Texas at Austin, 1 University Station-C0930, Austin, TX 78712, USA

Received 23 December 2010; Revised 2 April 2011; Accepted 3 May 2011

Academic Editor: Martin J. Genner

Copyright © 2011 Peter D. Dijkstra and Ton G. G. Groothuis. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


It has been suggested that intrasexual competition can be a source of negative frequency-dependent selection, causing agonistic character displacement and facilitating speciation and coexistence of (sibling) species. In this paper we synthesise the evidence that male-male and female-female competition contributes to cichlid diversification, showing that competition is stronger among same-coloured individuals than those with different colours. We argue that intrasexual selection is more complex because there are several examples where males do not bias aggression towards their own type. In addition, sibling species or colour morphs often show asymmetric dominance relationships. We briefly discuss potential mechanisms that might promote the maintenance of covariance between colour and aggression-related traits even in the face of gene-flow. We close by proposing several avenues for future studies that might shed more light on the role of intrasexual competition in cichlid diversification.