Relationship between flightlessness and brain morphology among Rallidae

Studies have suggested that the brain morphology and flight ability of Aves are interrelated; however, such a relationship has not been thoroughly investigated. This study aimed to examine whether flight ability, volant or flightless, affects brain morphology (size and shape) in the Rallidae, which...

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Bibliographic Details
Published in:Journal of anatomy 2022-09, Vol.241 (3), p.776-788
Main Authors: Nakao, Tatsuro, Yamasaki, Takeshi, Ogihara, Naomichi, Shimada, Masaki
Format: Article
Language:English
Subjects:
3D geometric morphometrics
Analysis of covariance
Aves
Body mass
Body size
Body weight
Brain
Computed tomography
Energy metabolism
Flight
foramen magnum
Morphology
Original
Original Paper
phylogenetic ANCOVA
Phylogeny
Principal components analysis
rails
Rallidae
Skull
Telencephalon
tool‐using behavior
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Summary:Studies have suggested that the brain morphology and flight ability of Aves are interrelated; however, such a relationship has not been thoroughly investigated. This study aimed to examine whether flight ability, volant or flightless, affects brain morphology (size and shape) in the Rallidae, which has independently evolved to adapt secondary flightlessness multiple times within a single taxonomic group. Brain endocasts were extracted from computed tomography images of the crania, measured by 3D geometric morphometrics, and were analyzed using principal component analysis. The results of phylogenetic ANCOVA showed that flightless rails have brain sizes and shapes that are significantly larger than and different from those of volant rails, even after considering the effects of body mass and brain size respectively. Flightless rails tended to have a wider telencephalon and more inferiorly positioned foramen magnum than volant rails. Although the brain is an organ that requires a large amount of metabolic energy, reduced selective pressure for a lower body weight may have allowed flightless rails to have larger brains. The evolution of flightlessness may have changed the position of the foramen magnum downward, which would have allowed the support of the heavier cranium. The larger brain may have facilitated the acquisition of cognitively advanced behavior, such as tool‐using behavior, among rails. Flightless rails have brain sizes and shapes that are significantly larger than and different from those of volant rails. Flightless rails tended to have a wider telencephalon and more inferiorly positioned foramen magnum than volant rails. The larger brain may have facilitated the acquisition of cognitively advanced behavior, such as tool‐using behavior, among rails.
ISSN:0021-8782
1469-7580
1469-7580
DOI:10.1111/joa.13690