Quantitative genetic analysis of brain size variation in sticklebacks: support for the mosaic model of brain evolution

Noreikienė, Kristina; Herczeg, Gábor; Gonda, Abigél; Balázs, Gergely; Husby, Arild; Merilä, Juha

doi:10.1098/rspb.2015.1008

Cited by 49 publications

(86 citation statements)

References 54 publications

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“…Overall volume and neuron number of individual sub-components may also have independent genetic bases [47,48], implying that developmental models tying one to the other will have limited predictive power. Evidence for genetic independence between brain components has also been reported in sticklebacks and between chicken breeds [49,50]. In sticklebacks, genetic correlations between brain components are significantly less than unity, despite a relatively high correlation between brain and body size [49].…”

Section: (A) Selective Decoupling Of Coevolving Traitsmentioning

confidence: 89%

“…Evidence for genetic independence between brain components has also been reported in sticklebacks and between chicken breeds [49,50]. In sticklebacks, genetic correlations between brain components are significantly less than unity, despite a relatively high correlation between brain and body size [49]. Hence, even where body size does constrain the evolution of brain size, brain structure may still undergo adaptive reorganization.…”

Section: (A) Selective Decoupling Of Coevolving Traitsmentioning

confidence: 94%

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Brain evolution and development: adaptation, allometry and constraint

2016

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Phenotypic traits are products of two processes: evolution and development. But how do these processes combine to produce integrated phenotypes? Comparative studies identify consistent patterns of covariation, or allometries, between brain and body size, and between brain components, indicating the presence of significant constraints limiting independent evolution of separate parts. These constraints are poorly understood, but in principle could be either developmental or functional. The developmental constraints hypothesis suggests that individual components (brain and body size, or individual brain components) tend to evolve together because natural selection operates on relatively simple developmental mechanisms that affect the growth of all parts in a concerted manner. The functional constraints hypothesis suggests that correlated change reflects the action of selection on distributed functional systems connecting the different sub-components, predicting more complex patterns of mosaic change at the level of the functional systems and more complex genetic and developmental mechanisms. These hypotheses are not mutually exclusive but make different predictions. We review recent genetic and neurodevelopmental evidence, concluding that functional rather than developmental constraints are the main cause of the observed patterns. How brains evolve: the importance of scaling relationshipsThe components of any adaptive complex by definition undergo coordinated evolution. Brains, bodies and individual brain components therefore exhibit distinctive patterns of correlated evolution. But what do these patterns tell us about the roles of adaptation and constraint in shaping phenotypes? In particular, how and to what extent do constraints imposed by shared developmental programmes dictate allometric relationships between components, limiting their response to selection? These questions have shaped two key debates central to how we view brain evolution: the functional relevance of brain size and the adaptive potential of brain structure [1][2][3]. These debates hinge on whether observed patterns of scaling relationships, between brain and body size or different brain components, are the product of selection to maintain functional correspondence or constraints imposed by shared developmental programmes. Crucially, however, a sound understanding of the significance of scaling relationships in brain evolution has been limited by a lack of data on the genetic and developmental mechanisms that regulate brain size and structure. Here we discuss how recent discoveries about the genetic control of neural development shed new light on the issue.(a) Brain: body coevolution and the importance of size

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Section: (A) Selective Decoupling Of Coevolving Traitsmentioning

confidence: 89%

Section: (A) Selective Decoupling Of Coevolving Traitsmentioning

confidence: 94%

Brain evolution and development: adaptation, allometry and constraint

2016

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“…The details of molecular sexing procedures are given in Noreikiene et al. (2015). In short, sex identification was based on amplifying a part of the 3′UTR of the NADP‐dependent isocitrate dehydrogenase ( Idh ) locus, which yields two bands for male and one band for female three‐spined sticklebacks (Peichel et al., 2004) in the populations used in this study (cf.…”

Section: Methodsmentioning

confidence: 99%

Environmental enrichment, sexual dimorphism, and brain size in sticklebacks

Toli

Noreikienė

DeFaveri

et al. 2017

Ecology and Evolution

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Evidence for phenotypic plasticity in brain size and the size of different brain parts is widespread, but experimental investigations into this effect remain scarce and are usually conducted using individuals from a single population. As the costs and benefits of plasticity may differ among populations, the extent of brain plasticity may also differ from one population to another. In a common garden experiment conducted with three‐spined sticklebacks (Gasterosteus aculeatus) originating from four different populations, we investigated whether environmental enrichment (aquaria provided with structural complexity) caused an increase in the brain size or size of different brain parts compared to controls (bare aquaria). We found no evidence for a positive effect of environmental enrichment on brain size or size of different brain parts in either of the sexes in any of the populations. However, in all populations, males had larger brains than females, and the degree of sexual size dimorphism (SSD) in relative brain size ranged from 5.1 to 11.6% across the populations. Evidence was also found for genetically based differences in relative brain size among populations, as well as for plasticity in the size of different brain parts, as evidenced by consistent size differences among replicate blocks that differed in their temperature.

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“…Furthermore, variation in the size of specific regions that have known functions may point to the ecological and evolutionary processes that have led to this brain variation. For example, changes in brain morphology could result from a concerted increase or decrease in size across all brain regions, or in a mosaic fashion where only one or a few regions change in size while other regions remain unchanged [Finlay and Darlington, 1995;Barton and Harvey, 2000;Gonzalez-Voyer and Kolm, 2010;Noreikiene et al, 2015]. Thus, studies investigating size variation in specific brain regions are important for determining what factors influence patterns of change in brain size.…”

Section: Introductionmentioning

confidence: 99%

Food Web Structure Shapes the Morphology of Teleost Fish Brains

Edmunds¹,

McCann²,

Laberge³

2016

Brain Behav Evol

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Previous work showed that teleost fish brain size correlates with the flexible exploitation of habitats and predation abilities in an aquatic food web. Since it is unclear how regional brain changes contribute to these relationships, we quantitatively examined the effects of common food web attributes on the size of five brain regions in teleost fish at both within-species (plasticity or natural variation) and between-species (evolution) scales. Our results indicate that brain morphology is influenced by habitat use and trophic position, but not by the degree of littoral-pelagic habitat coupling, despite the fact that the total brain size was previously shown to increase with habitat coupling in Lake Huron. Intriguingly, the results revealed two potential evolutionary trade-offs: (i) relative olfactory bulb size increased, while relative optic tectum size decreased, across a trophic position gradient, and (ii) the telencephalon was relatively larger in fish using more littoral-based carbon, while the cerebellum was relatively larger in fish using more pelagic-based carbon. Additionally, evidence for a within-species effect on the telencephalon was found, where it increased in size with trophic position. Collectively, these results suggest that food web structure has fundamentally contributed to the shaping of teleost brain morphology.

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Quantitative genetic analysis of brain size variation in sticklebacks: support for the mosaic model of brain evolution

Cited by 49 publications

References 54 publications

Brain evolution and development: adaptation, allometry and constraint

Brain evolution and development: adaptation, allometry and constraint

Environmental enrichment, sexual dimorphism, and brain size in sticklebacks

Food Web Structure Shapes the Morphology of Teleost Fish Brains

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