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Divergent hormonal responses to social competition in closely related species of haplochromine cichlid fish

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  • Peter D. Dijkstra, The University of Texas at Austin, Unknown
  • Machteld Nicolette Verzijden, The Institute of Biology Leiden, Gorlaeus Laboratoria, Leiden University, Department of Biology, Texas A&M University, Denmark
  • Ton G G Groothuis, Centre for Behavioural Biology, School of Clinical Veterinary Science, University of Bristol, Unknown
  • Hans A. Hofmann, The University of Texas at Austin, Unknown

The diverse cichlid species flocks of the East African lakes provide a classical example of adaptive radiation. Territorial aggression is thought to influence the evolution of phenotypic diversity in this system. Most vertebrates mount hormonal (androgen, glucocorticoid) responses to a territorial challenge. These hormones, in turn, influence behavior and multiple aspects of physiology and morphology. Examining variation in competition-induced hormone secretion patterns is thus fundamental to an understanding of the mechanisms of phenotypic diversification. We test here the hypothesis that diversification in male aggression has been accompanied by differentiation in steroid hormone levels. We studied two pairs of sibling species from Lake Victoria belonging to the genera Pundamilia and Mbipia. The two genera are ecologically differentiated, while sibling species pairs differ mainly in male color patterns. We found that aggression directed toward conspecific males varied between species and across genera: Pundamilia nyererei males were more aggressive than Pundamilia pundamilia males, and Mbipia mbipi males were more aggressive than Mbipia lutea males. Males of both genera exhibited comparable attack rates during acute exposure to a novel conspecific intruder, while Mbipia males were more aggressive than Pundamilia males during continuous exposure to a conspecific rival, consistent with the genus difference in feeding ecology. Variation in aggressiveness between genera, but not between sibling species, was reflected in androgen levels. We further found that M. mbipi displayed lower levels of cortisol than M. lutea. Our results suggest that concerted divergence in hormones and behavior might play an important role in the rapid speciation of cichlid fishes.

Original languageEnglish
JournalHormones and Behavior
Pages (from-to)518-526
Number of pages9
Publication statusPublished - 1 Apr 2012
Externally publishedYes

    Research areas

  • 11-Ketotestosterone, Cichlid, Cortisol, Male-male competition, Speciation, Steroid, Teleost, Testosterone

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