Adaptive sequence evolution in a color gene involved in the formation of the characteristic egg-dummies of male haplochr
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BioMed Central
Open Access
Research article
Adaptive sequence evolution in a color gene involved in the formation of the characteristic egg-dummies of male haplochromine cichlid fishes Walter Salzburger†1,2,3, Ingo Braasch†1,4 and Axel Meyer*1 Address: 1Lehrstuhl für Zoologie und Evolutionsbiologie, Department of Biology, University Konstanz, 78457 Konstanz, Germany, 2Department of Ecology and Evolution, University of Lausanne, 1015 Lausanne, Switzerland, 3Zoologisches Institut der Universität Basel, Evolutionsbiologie, Universität Basel, 4051 Basel, Switzerland and 4Physiological Chemistry I, University of Würzburg, 97074 Würzburg, Germany Email: Walter Salzburger - [email protected]; Ingo Braasch - [email protected]; Axel Meyer* - [email protected] * Corresponding author †Equal contributors
Published: 15 November 2007 BMC Biology 2007, 5:51
doi:10.1186/1741-7007-5-51
Received: 20 September 2007 Accepted: 15 November 2007
This article is available from: http://www.biomedcentral.com/1741-7007/5/51 © 2007 Salzburger et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract Background: The exceptionally diverse species flocks of cichlid fishes in East Africa are prime examples of parallel adaptive radiations. About 80% of East Africa's more than 1 800 endemic cichlid species, and all species of the flocks of Lakes Victoria and Malawi, belong to a particularly rapidly evolving lineage, the haplochromines. One characteristic feature of the haplochromines is their possession of egg-dummies on the males' anal fins. These egg-spots mimic real eggs and play an important role in the mating system of these maternal mouthbrooding fish. Results: Here, we show that the egg-spots of haplochromines are made up of yellow pigment cells, xanthophores, and that a gene coding for a type III receptor tyrosine kinase, colony-stimulating factor 1 receptor a (csf1ra), is expressed in egg-spot tissue. Molecular evolutionary analyses reveal that the extracellular ligand-binding and receptor-interacting domain of csf1ra underwent adaptive sequence evolution in the ancestral lineage of the haplochromines, coinciding with the emergence of egg-dummies. We also find that csf1ra is expressed in the egg-dummies of a distantly related cichlid species, the ectodine cichlid Ophthalmotilapia ventralis, in which markings with similar functions evolved on the pelvic fin in convergence to those of the haplochromines. Conclusion: We conclude that modifications of existing signal transduction mechanisms might have evolved in the haplochromine lineage in association with the origination of anal fin eggdummies. That positive selection has acted during the evolution of a color gene that seems to be involved in the morphogenesis of a sexually selected trai
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