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Open Access Highly Accessed Research article

Phenotypic integration of brain size and head morphology in Lake Tanganyika Cichlids

Masahito Tsuboi1*, Alejandro Gonzalez-Voyer2 and Niclas Kolm3

Author Affiliations

1 Department of Animal Ecology, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, 75236 Uppsala, Sweden

2 Department of Integrative Ecology, Estación Biológica de Doñana – Consejo Superior de Investigaciónes Científicas (EBD–CSIC), Av Américo Vespucio s/n, 41092 Sevilla, Spain

3 Department of Zoology, Stockholm University, Svante Arrhenius väg 18B, 10691 Stockholm, Sweden

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BMC Evolutionary Biology 2014, 14:39  doi:10.1186/1471-2148-14-39

Published: 4 March 2014



Phenotypic integration among different anatomical parts of the head is a common phenomenon across vertebrates. Interestingly, despite centuries of research into the factors that contribute to the existing variation in brain size among vertebrates, little is known about the role of phenotypic integration in brain size diversification. Here we used geometric morphometrics on the morphologically diverse Tanganyikan cichlids to investigate phenotypic integration across key morphological aspects of the head. Then, while taking the effect of shared ancestry into account, we tested if head shape was associated with brain size while controlling for the potentially confounding effect of feeding strategy.


The shapes of the anterior and posterior parts of the head were strongly correlated, indicating that the head represents an integrated morphological unit in Lake Tanganyika cichlids. After controlling for phylogenetic non-independence, we also found evolutionary associations between head shape, brain size and feeding ecology.


Geometric morphometrics and phylogenetic comparative analyses revealed that the anterior and posterior parts of the head are integrated, and that head morphology is associated with brain size and feeding ecology in Tanganyikan cichlid fishes. In light of previous results on mammals, our results suggest that the influence of phenotypic integration on brain diversification is a general process.

Phenotypic integration; Geometric morphometrics; Phylogenetic comparative analysis; Lake Tanganyika cichlid; Brain evolution; Constraints