Are Urban Vertebrates City Specialists, Artificial Habitat Exploiters, or Environmental Generalists?

Ducatez S., Sayol F., Sol D., Lefebvre L. (2018) Are Urban Vertebrates City Specialists, Artificial Habitat Exploiters, or Environmental Generalists?. Integrative and comparative biology. 58: 929-938.
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Doi: 10.1093/icb/icy101

Resum:

Although urbanization is a major threat to biodiversity, some species are able to thrive in cities. This might be because they have specific adaptations to urban conditions, because they are able to cope with artificial habitats in general or because they are generalists that can live in a wide range of conditions. We use the latest version of the IUCN database to distinguish these possibilities in 25,985 species of the four classes of terrestrial vertebrates with the help of phylogenetically controlled methods. We first compare species occurrence in cities with that of the five other artificial habitats recognized by the IUCN and use principal components analyses to ask which of these most resembles cities. We then test whether urban species have a wider habitat breadth than species occurring in other, non-urban, artificial habitats, as well as species that occur only in natural habitats. Our results suggest that the proportion of terrestrial vertebrates that occur in urban environments is small and that, among the species that do occur in cities, the great majority also occur in other artificial habitats. Our data also show that the presence of terrestrial vertebrates in urban habitats is skewed in favor of habitat generalists. In birds and mammals, species occurrence in urban areas is most similar to that of rural gardens, while in reptiles and amphibians, urban areas most resemble pasture and arable land. Our study suggests that cities are likely not unique, as is often thought, and may resemble other types of artificial environments, which urban exploiters can adapt to because of their wide habitat breadth.

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Predictable evolution towards larger brains in birds colonizing oceanic islands

Sayol F., Downing P.A., Iwaniuk A.N., Maspons J., Sol D. (2018) Predictable evolution towards larger brains in birds colonizing oceanic islands. Nature Communications. 9: 0-0.
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Doi: 10.1038/s41467-018-05280-8

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Theory and evidence suggest that some selective pressures are more common on islands than in adjacent mainland habitats, leading evolution to follow predictable trends. The existence of predictable evolutionary trends has nonetheless been difficult to demonstrate, mainly because of the challenge of separating in situ evolution from sorting processes derived from colonization events. Here we use brain size measurements of >1900 avian species to reveal the existence of one such trend: increased brain size in island dwellers. Based on sister-taxa comparisons and phylogenetic ancestral trait estimations, we show that species living on islands have relatively larger brains than their mainland relatives and that these differences mainly reflect in situ evolution rather than varying colonization success. Our findings reinforce the view that in some instances evolution may be predictable, and yield insight into why some animals evolve larger brains despite substantial energetic and developmental costs. © 2018, The Author(s).

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Relative brain size and its relation with the associative pallium in birds

Sayol F., Lefebvre L., Sol D. (2016) Relative brain size and its relation with the associative pallium in birds. Brain, Behavior and Evolution. 87: 69-77.
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Doi: 10.1159/000444670

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Despite growing interest in the evolution of enlarged brains, the biological significance of brain size variation remains controversial. Much of the controversy is over the extent to which brain structures have evolved independently of each other (mosaic evolution) or in a coordinated way (concerted evolution). If larger brains have evolved by the increase of different brain regions in different species, it follows that comparisons of the whole brain might be biologically meaningless. Such an argument has been used to criticize comparative attempts to explain the existing variation in whole-brain size among species. Here, we show that pallium areas associated with domain-general cognition represent a large fraction of the entire brain, are disproportionally larger in large-brained birds and accurately predict variation in the whole brain when allometric effects are appropriately accounted for. While this does not question the importance of mosaic evolution, it suggests that examining specialized, small areas of the brain is not very helpful for understanding why some birds have evolved such large brains. Instead, the size of the whole brain reflects consistent variation in associative pallium areas and hence is functionally meaningful for comparative analyses. © 2016 S. Karger AG, Basel.

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Environmental variation and the evolution of large brains in birds

Sayol, F., Maspons, J., Lapiedra, O., Iwaniuk, A.N., Székely, T., Sol, D. (2016) Environmental variation and the evolution of large brains in birds. Nature Communications. 7: 0-0.
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Doi: 10.1038/ncomms13971

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The life-history basis of behavioural innovations

Sol D., Sayol F., Ducatez S., Lefebvre L. (2016) The life-history basis of behavioural innovations. Philosophical Transactions of the Royal Society B: Biological Sciences. 371: 0-0.
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Doi: 10.1098/rstb.2015.0187

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The evolutionary origin of innovativeness remains puzzling because innovating means responding to novel or unusual problems and hence is unlikely to be selected by itself. A plausible alternative is considering innovativeness as a co-opted product of traits that have evolved for other functions yet together predispose individuals to solve problems by adopting novel behaviours. However, this raises the question of why these adaptations should evolve together in an animal. Here, we develop the argument that the adaptations enabling animals to innovate evolve together because they are jointly part of a life-history strategy for coping with environmental changes. In support of this claim, we present comparative evidence showing that in birds, (i) innovative propensity is linked to life histories that prioritize future over current reproduction, (ii) the link is in part explained by differences in brain size, and (iii) innovative propensity and life-history traits may evolve together in generalist species that frequently expose themselves to novel or unusual conditions. Combined with previous evidence, these findings suggest that innovativeness is not a specialized adaptation but more likely part of a broader general adaptive system to cope with changes in the environment. © 2016 The Author(s) Published by the Royal Society. All rights reserved.

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