| 1. |
- Jiménez-Ortega, Dante, et al.
(författare)
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Long life evolves in large-brained bird lineages
- 2020
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Ingår i: Evolution. - : Wiley. - 0014-3820 .- 1558-5646. ; 74:12, s. 2617-2628
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Tidskriftsartikel (refereegranskat)abstract
- The brain is an energetically costly organ that consumes a disproportionate amount of resources. Species with larger brains relative to their body size have slower life histories, with reduced output per reproductive event and delayed development times that can be offset by increasing behavioral flexibility. The cognitive buffer hypothesis maintains that large brain size decreases extrinsic mortality due to greater behavioral flexibility, leading to a longer lifespan. Alternatively, slow life histories, and long lifespan can be a pre-adaptation for the evolution of larger brains. Here, we use phylogenetic path analysis to contrast different evolutionary scenarios and disentangle direct and indirect relationships between brain size, body size, life history, and longevity across 339 altricial and precocial bird species. Our results support both a direct causal link between brain size and lifespan, and an indirect effect via other life history traits. These results indicate that large brain size engenders longer life, as proposed by the cognitive buffer hypothesis.
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| 2. |
- Kotrschal, Alexander, et al.
(författare)
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Artificial selection on relative brain size in the guppy reveals costs and benefits of evolving a larger brain
- 2013
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Ingår i: Current Biology. - : Elsevier BV. - 0960-9822 .- 1879-0445. ; 23:2, s. 168-171
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Tidskriftsartikel (refereegranskat)abstract
- The large variation in brain size that exists in the animal kingdom has been suggested to have evolved through the balance between selective advantages of greater cognitive ability and the prohibitively high energy demands of a larger brain (the "expensive-tissue hypothesis" [1]). Despite over a century of research on the evolution of brain size, empirical support for the trade-off between cognitive ability and energetic costs is based exclusively on correlative evidence [2], and the theory remains controversial [3, 4]. Here we provide experimental evidence for costs and benefits of increased brain size. We used artificial selection for large and small brain size relative to body size in a live-bearing fish, the guppy (Poecilia reticulata), and found that relative brain size evolved rapidly in response to divergent selection in both sexes. Large-brained females outperformed small-brained females in a numerical learning assay designed to test cognitive ability. Moreover, large-brained lines, especially males, developed smaller guts, as predicted by the expensive-tissue hypothesis [1], and produced fewer offspring. We propose that the evolution of brain size is mediated by a functional trade-off between increased cognitive ability and reproductive performance and discuss the implications of these findings for vertebrate brain evolution.
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| 3. |
- Kotrschal, Alexander, et al.
(författare)
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Positive genetic correlation between brain size and sexual traits in male guppies artificially selected for brain size
- 2015
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 28:4, s. 841-850
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Tidskriftsartikel (refereegranskat)abstract
- Brain size is an energetically costly trait to develop and maintain. Investments into other costly aspects of an organism's biology may therefore place important constraints on brain size evolution. Sexual traits are often costly and could therefore be traded off against neural investment. However, brain size may itself be under sexual selection through mate choice on cognitive ability. Here, we use guppy (Poecilia reticulata) lines selected for large and small brain size relative to body size to investigate the relationship between brain size, a large suite of male primary and secondary sexual traits, and body condition index. We found no evidence for trade-offs between brain size and sexual traits. Instead, larger-brained males had higher expression of several primary and precopulatory sexual traits - they had longer genitalia, were more colourful and developed longer tails than smaller-brained males. Larger-brained males were also in better body condition when housed in single-sex groups. There was no difference in post-copulatory sexual traits between males from the large- and small-brained lines. Our data do not support the hypothesis that investment into sexual traits is an important limiting factor to brain size evolution, but instead suggest that brain size and several sexual traits are positively genetically correlated.
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| 4. |
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| 5. |
- Maklakov, Alexei A., et al.
(författare)
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Brains and the city : big-brained passerine birds succeed in urban environments
- 2011
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Ingår i: Biology Letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 7:5, s. 730-732
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Tidskriftsartikel (refereegranskat)abstract
- Urban regions are among the most human-altered environments on Earth and they are poised for rapid expansion following population growth and migration. Identifying the biological traits that determine which species are likely to succeed in urbanized habitats is important for predicting global trends in biodiversity. We provide the first evidence for the intuitive yet untested hypothesis that relative brain size is a key factor predisposing animals to successful establishment in cities. We apply phylogenetic mixed modelling in a Bayesian framework to show that passerine species that succeed in colonizing at least one of 12 European cities are more likely to belong to big-brained lineages than species avoiding these urban areas. These data support findings linking relative brain size with the ability to persist in novel and changing environments in vertebrate populations, and have important implications for our understanding of recent trends in biodiversity.
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| 6. |
- Maklakov, Alexei A., et al.
(författare)
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Brains and the city in passerine birds : re-analysis and confirmation of the original result
- 2013
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Ingår i: Biology Letters. - : The Royal Society. - 1744-9561 .- 1744-957X. ; 9:6, s. 20130859-
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Tidskriftsartikel (refereegranskat)abstract
- Our original paper [1] included two Bayesian analyses [2] of the association between brain size and the probability of a passerine species of bird breeding in the city centre—at the level of families and at the level of individual species—with both analyses suggesting the same pattern. It has since been brought to our attention that in one of the analyses at the level of individual species, the residual variance was not fixed to 1 resulting in overestimation of the variance. We re-ran the analysis using fixed residual variance and the results support the original conclusion that relative brain size is associated with breeding in the city centre (ln brain size: posterior mean, 324.53, 95% credibility interval, 52.61–601.35; ln body size: posterior mean, −276.22, 95% credibility interval, −490.60 to −70.32). Furthermore, we applied a complimentary approach using logistic regression to test whether brain size predicts breeding in the city centre (yes/no) without accounting for phylogeny. This analysis also resulted in a significant positive association between brain size and breeding in city centres (likelihood ratio tests: ln brain size: d.f. = 1, χ2 = 11.08, p = 0.0009; ln body size: d.f. = 1, χ2 = 11.26, p = 0.0008). Thus, our results are confirmed by both phylogenetic and non-phylogenetic analyses.
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