Fast running restricts evolutionary change of the vertebral column in mammals

Galis F, Carrier DR, van Alphen J, van der Mije SD, Van Dooren TJM, Metz JAJ, & ten Broek CMA (2014). Fast running restricts evolutionary change of the vertebral column in mammals. Proceedings of the National Academy of Sciences 111 (31): 11401-11406. DOI:10.1073/pnas.1401392111.

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Abstract

The mammalian vertebral column is highly variable, reflecting adaptations to a wide range of lifestyles, from burrowing in moles to flying in bats. However, in many taxa, the number of trunk vertebrae is surprisingly constant. We argue that this constancy results from strong selection against initial changes of these numbers in fast running and agile mammals, whereas such selection is weak in slower-running, sturdier mammals. The rationale is that changes of the number of trunk vertebrae require homeotic transformations from trunk into sacral vertebrae, or vice versa, and mutations toward such transformations generally produce transitional lumbosacral vertebrae that are incompletely fused to the sacrum. We hypothesize that such incomplete homeotic transformations impair flexibility of the lumbosacral joint and thereby threaten survival in species that depend on axial mobility for speed and agility. Such transformations will only marginally affect performance in slow, sturdy species, so that sufficient individuals with transitional vertebrae survive to allow eventual evolutionary changes of trunk vertebral numbers. We present data on fast and slow carnivores and artiodactyls and on slow afrotherians and monotremes that strongly support this hypothesis. The conclusion is that the selective constraints on the count of trunk vertebrae stem from a combination of developmental and biomechanical constraints.

Item Type: Article
Uncontrolled Keywords: Body plans; Evolutionary conservation; Stabilizing selection; Locomotion; Eco-Evo-Devo; Musculoskeletal system
Research Programs: Evolution and Ecology (EEP)
Bibliographic Reference: PNAS; 111(31):11401-11406 (5 August 2014) (Published online 14 July 2014)
Depositing User: IIASA Import
Date Deposited: 15 Jan 2016 08:50
Last Modified: 23 Aug 2016 09:26
URI: http://pure.iiasa.ac.at/10868

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