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Evolution of brain-body allometry in Lake Tanganyika cichlids
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Animal ecology.ORCID iD: 0000-0002-0144-2893
Stockholm Univ, Dept Zool Ethol, Svante Arrhenius Vag 18B, SE-10691 Stockholm, Sweden.
Stockholm Univ, Dept Zool Ethol, Svante Arrhenius Vag 18B, SE-10691 Stockholm, Sweden.
Stockholm Univ, Dept Zool Ethol, Svante Arrhenius Vag 18B, SE-10691 Stockholm, Sweden.
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2016 (English)In: Evolution, ISSN 0014-3820, E-ISSN 1558-5646, Vol. 70, no 7, 1559-1568 p.Article in journal (Refereed) Published
Abstract [en]

Brain size is strongly associated with body size at all taxonomic levels. This relationship has been hypothesized to be an important constraint on adaptive brain size evolution. The essential assumption of this idea is that allometry has a limited ability to evolve, and that evolution of relative brain size is therefore constrained to occur along the direction of static (i.e. within species) allometry. However, recent studies have reported mixed support for this view. Here, we examine if static allometry has affected the rate of relative brain size evolution in Lake Tanganyika cichlids. The evolution of brain-body allometry showed a recent rapid divergence whereas brain size evolution represented a more gradual phenotypic divergence across the history of diversification. Accordingly, we found no support for that static allometry affected the rate of absolute or relative brain size evolution in this group. Instead, we detected low, but existing evolvability of static allometry. Moreover, static allometry evolved faster in species with relatively small and large brains than in species with medium brain size. We propose that a combination of allometric constraints and partial evolvability of static allometry have allowed for independent evolution of brain size in Lake Tanganyika cichlids. Overall, our results demonstrate a complex, yet important, role of brain-body allometry in brain size evolution. 

Place, publisher, year, edition, pages
2016. Vol. 70, no 7, 1559-1568 p.
National Category
Evolutionary Biology
URN: urn:nbn:se:uu:diva-262069DOI: 10.1111/evo.12965ISI: 000380023200011PubMedID: 27241216OAI: oai:DiVA.org:uu-262069DiVA: diva2:852168
Helge Ax:son Johnsons stiftelse Swedish Research Council, 621-2012-3624

Title in Thesis list of papers: Brain size evolution under allometric constraints in Lake Tanganyika cichlids

Available from: 2015-09-08 Created: 2015-09-08 Last updated: 2016-09-08Bibliographically 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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