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Open Access Highly Accessed Research article

Male mate choice scales female ornament allometry in a cichlid fish

Sebastian A Baldauf1*, Theo CM Bakker1, Fabian Herder2, Harald Kullmann3 and Timo Thünken1

Author Affiliations

1 Institute for Evolutionary Biology and Ecology, University of Bonn, An der Immenburg 1, 53121 Bonn, Germany

2 Zoologisches Forschungsmuseum Alexander Koenig, Adenauerallee 160, 53113 Bonn, Germany

3 Zentrum für Didaktik der Biologie, University of Münster, Hindenburgplatz 34, 48143 Münster, Germany

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BMC Evolutionary Biology 2010, 10:301  doi:10.1186/1471-2148-10-301

Published: 8 October 2010

Abstract

Background

Studies addressing the adaptive significance of female ornamentation have gained ground recently. However, the expression of female ornaments in relation to body size, known as trait allometry, still remains unexplored. Here, we investigated the allometry of a conspicuous female ornament in Pelvicachromis taeniatus, a biparental cichlid that shows mutual mate choice and ornamentation. Females feature an eye-catching pelvic fin greatly differing from that of males.

Results

We show that allometry of the female pelvic fin is scaled more positively in comparison to other fins. The pelvic fin exhibits isometry, whereas the other fins (except the caudal fin) show negative allometry. The size of the pelvic fin might be exaggerated by male choice because males prefer female stimuli that show a larger extension of the trait. Female pelvic fin size is correlated with individual condition, suggesting that males can assess direct and indirect benefits.

Conclusions

The absence of positive ornament allometry might be a result of sexual selection constricted by natural selection: fins are related to locomotion and thus may be subject to viability selection. Our study provides evidence that male mate choice might scale the expression of a female sexual ornament, and therefore has implications for the understanding of the relationship of female sexual traits with body size in species with conventional sex-roles.