Assessing the levels of functional adaptation: finite element analysis reveals species, hybrid, and sexual variation in the biomechanics of African cichlid mandibles

McWhinnie, K., Gibson, J., Gislason, M., Tanner, E. , Windmill, J., Albertson, R. C. and Parsons, K. (2022) Assessing the levels of functional adaptation: finite element analysis reveals species, hybrid, and sexual variation in the biomechanics of African cichlid mandibles. Evolutionary Biology, 49(2), pp. 205-220. (doi: 10.1007/s11692-022-09566-0)

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To understand how adaptive divergence emerges it is essential to examine the function of phenotypic traits along a continuum. For vertebrates, the mandible provides a key link with foraging and other important activities which has made it highly relevant for investigations of biomechanical change. Variation in mandible shape is known to correspond with ecology but its function is often only investigated between distinct species. However, for such divergence to occur and be maintained selection likely draws from many sources of biomechanical variation. African cichlids represent an exemplar model for understanding how such processes unfold with mandible variation existing between species, sexes, and is likely generated in nature by the potential for hybridization. We explored such mandible variation through a finite element modelling approach and predicted that hybrids and females would have reduced functional capabilities, the former in line with disruptive selection and the latter due to potential trade-offs incurred by maternal mouthbrooding in Malawian haplochromines. We revealed evidence of structural adaptations between Tropheops ‘Red Cheek’ and Labeotrophues fuelleborni that impacted the dispersion of mechanical stress in ways that matched the foraging of these species. Also, hybrids showed higher stresses relative to both species across the mandible. Sexual dimorphism in stress handling was evident despite minor differences in shape with males showing enhanced load resistance. However, in hybrids it appeared that males were disadvantaged relative to females, and displayed asymmetry in load handling. Together, these results show evidence of species and sex based biomechanical variation, that could be targeted by divergent selection.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Windmill, Professor James and McWhinnie, Kirsty and Tanner, Professor Kathleen and Parsons, Dr Kevin and Gislason, Dr Magnus
Authors: McWhinnie, K., Gibson, J., Gislason, M., Tanner, E., Windmill, J., Albertson, R. C., and Parsons, K.
College/School:College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
Journal Name:Evolutionary Biology
ISSN (Online):1934-2845
Published Online:22 March 2022
Copyright Holders:Copyright © 2022 The Authors
First Published:First published in Evolutionary Biology 49(2): 205-220
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
190906EPSRC 2015 DTPMary Beth KneafseyEngineering and Physical Sciences Research Council (EPSRC)EP/M508056/1Research and Innovation Services