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Morphological adaptations for relatively larger brains in hummingbird skulls

A common allometric pattern called Haller's Rule states that small species have relatively larger brains and eyes than larger species of the same taxonomic group. This pattern imposes drastic structural changes and energetic costs on small species to produce and maintain a disproportionate amou...

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Autores principales: Ocampo, Diego, Barrantes, Gilbert, Uy, J. Albert C.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2018
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6238128/
https://www.ncbi.nlm.nih.gov/pubmed/30464820
http://dx.doi.org/10.1002/ece3.4513
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author Ocampo, Diego
Barrantes, Gilbert
Uy, J. Albert C.
author_facet Ocampo, Diego
Barrantes, Gilbert
Uy, J. Albert C.
author_sort Ocampo, Diego
collection PubMed
description A common allometric pattern called Haller's Rule states that small species have relatively larger brains and eyes than larger species of the same taxonomic group. This pattern imposes drastic structural changes and energetic costs on small species to produce and maintain a disproportionate amount of nervous tissue. Indeed, several studies have shown the significant metabolic costs of having relatively larger brains; however, little is known about the structural constraints and adaptations required for housing these relatively larger brains and eyes. Because hummingbirds include the smallest birds, they are ideal for exploring how small species evolve morphological adaptations for housing relatively larger brain and eyes. We here present results from a comparative study of hummingbirds and show that the smallest species have the lowest levels of ossification, the most compact braincases, and relatively larger eye sockets, but lower eye/head proportion, than larger species. In contrast to Passerines, skull ossification in hummingbirds correlates with body and brain size but not with age. Correlation of these skull traits with body size might represent adaptations to facilitate housing relatively larger brain and eyes, rather than just heterochronic effects related to change in body size. These structural changes in skull traits allow small animals to accommodate disproportionately larger brains and eyes without further increasing overall head size.
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spelling pubmed-62381282018-11-21 Morphological adaptations for relatively larger brains in hummingbird skulls Ocampo, Diego Barrantes, Gilbert Uy, J. Albert C. Ecol Evol Original Research A common allometric pattern called Haller's Rule states that small species have relatively larger brains and eyes than larger species of the same taxonomic group. This pattern imposes drastic structural changes and energetic costs on small species to produce and maintain a disproportionate amount of nervous tissue. Indeed, several studies have shown the significant metabolic costs of having relatively larger brains; however, little is known about the structural constraints and adaptations required for housing these relatively larger brains and eyes. Because hummingbirds include the smallest birds, they are ideal for exploring how small species evolve morphological adaptations for housing relatively larger brain and eyes. We here present results from a comparative study of hummingbirds and show that the smallest species have the lowest levels of ossification, the most compact braincases, and relatively larger eye sockets, but lower eye/head proportion, than larger species. In contrast to Passerines, skull ossification in hummingbirds correlates with body and brain size but not with age. Correlation of these skull traits with body size might represent adaptations to facilitate housing relatively larger brain and eyes, rather than just heterochronic effects related to change in body size. These structural changes in skull traits allow small animals to accommodate disproportionately larger brains and eyes without further increasing overall head size. John Wiley and Sons Inc. 2018-09-27 /pmc/articles/PMC6238128/ /pubmed/30464820 http://dx.doi.org/10.1002/ece3.4513 Text en © 2018 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd. This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
spellingShingle Original Research
Ocampo, Diego
Barrantes, Gilbert
Uy, J. Albert C.
Morphological adaptations for relatively larger brains in hummingbird skulls
title Morphological adaptations for relatively larger brains in hummingbird skulls
title_full Morphological adaptations for relatively larger brains in hummingbird skulls
title_fullStr Morphological adaptations for relatively larger brains in hummingbird skulls
title_full_unstemmed Morphological adaptations for relatively larger brains in hummingbird skulls
title_short Morphological adaptations for relatively larger brains in hummingbird skulls
title_sort morphological adaptations for relatively larger brains in hummingbird skulls
topic Original Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6238128/
https://www.ncbi.nlm.nih.gov/pubmed/30464820
http://dx.doi.org/10.1002/ece3.4513
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