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Phenotypic integration of brain size and head morphology in Lake Tanganyika Cichlids
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.
2014 (English)In: BMC Evolutionary Biology, ISSN 1471-2148, Vol. 14, 39- p.Article in journal (Refereed) Published
Abstract [en]

Background: 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. Results: 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. Conclusions: 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.

Place, publisher, year, edition, pages
2014. Vol. 14, 39- p.
Keyword [en]
Phenotypic integration, Geometric morphometrics, Phylogenetic comparative analysis, Lake Tanganyika cichlid, Brain evolution, Constraints
National Category
Biological Sciences
URN: urn:nbn:se:uu:diva-225106DOI: 10.1186/1471-2148-14-39ISI: 000334458900001OAI: oai:DiVA.org:uu-225106DiVA: diva2:719876
Available from: 2014-05-27 Created: 2014-05-27 Last updated: 2015-10-12Bibliographically approved
In thesis
1. Thinking in water: Brain size evolution in Cichlidae and Syngnathidae
Open this publication in new window or tab >>Thinking in water: Brain size evolution in Cichlidae and Syngnathidae
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Brain size varies greatly among vertebrates. It has been proposed that the diversity of brain size is produced and maintained through a balance of adaptations to different types and levels of cognitive ability and constraints for adaptive evolution. Phylogenetic comparative studies have made major contributions to our understanding of brain size evolution. However, previous studies have nearly exclusively focused on mammalian and avian taxa and almost no attempts have been made to investigate brain size evolution in ectothermic vertebrates.

In my thesis, I studied brain size evolution in two groups of fish with extreme diversity in ecology, morphology and life history, Cichlidae and Syngnathidae. Using phylogenetic comparative methods, I investigated four key questions in vertebrate brain size evolution; cognitive adaptation, sexual selection, phenotypic integration and energetic constraints.

I have demonstrated i) that phenotypic integration can link functionally unrelated traits, and this may constrain independent evolution of each part involved or promote concerted evolution of an integrated whole, ii) that brain-body static allometry constrains the direction of brain size evolution, even though the static-allometry showed ability to evolve, allowing evolution of relative brain size under allometric constraints, iii) that the energetic constraints of development and maintenance of brain tissue is an important factor in forming the diversity in brain size in cichlids and syngnathids, both at macroevolutionary and microevolutionary time scales, and iv) that adaptation for feeding and female mating competition may have played key roles in the adaptive evolution of brain size in pipefishes and seahorses. To conclude, my thesis shows the strong benefit of using fish as a model system to study brain size evolution with a phylogenetic comparative framework.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 50 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1286
brain evolution, phylogenetic comparative method, the expensive tissue hypothesis, cichlid, pipefish, seahorse
National Category
Evolutionary Biology
Research subject
Biology with specialization in Animal Ecology
urn:nbn:se:uu:diva-262216 (URN)978-91-554-9333-2 (ISBN)
Public defence
2015-10-29, Zootissalen, Villavägen 9, tr.2, Uppsala, 10:15 (English)
Available from: 2015-10-07 Created: 2015-09-10 Last updated: 2015-10-12

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