Facial asymmetry tracks genetic diversity among Gorilla subspecies

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McGrath, Kate and Eriksen, Amandine B. and García Martínez, Daniel and Galbany, Jordi and Gómez Robles, Aida and Massey, Jason S. and Fatica, M. and Glowacka, Halszka and Arbenz Smith, Keely and Muvunyi, Richard and Stoinski, Tara S. and Cranfield, Michael R. and Gilardi, Kirsten and Shalukoma, Chantal and Merode, Emmanuel de and Gilissen, Emmanuel and Tocheri, Matthew W. and McFarlin, Shannon C. and Heuzé, Yann (2022) Facial asymmetry tracks genetic diversity among Gorilla subspecies. Proceedings of the Royal Society B: Biological Sciences, 289 (1969). pp. 1-10. ISSN 0962-8452 Electronic: 1471-2954

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Official URL: https://doi.org/10.1098/rspb.2021.2564




Abstract

Mountain gorillas are particularly inbred compared to other gorillas and even the most inbred human populations. As mountain gorilla skeletal material accumulated during the 1970s, researchers noted their pronounced facial asymmetry and hypothesized that it reflects a population-wide chewing side preference. However, asymmetry has also been linked to environmental and genetic stress in experimental models. Here, we examine facial asymmetry in 114 crania from three Gorilla subspecies using 3D geometric morphometrics. We measure fluctuating asymmetry (FA), defined as random deviations from perfect symmetry, and population-specific patterns of directional asymmetry (DA). Mountain gorillas, with a current population size of about 1000 individuals, have the highest degree of facial FA (explaining 17% of total facial shape variation), followed by Grauer gorillas (9%) and western lowland gorillas (6%), despite the latter experiencing the greatest ecological and dietary variability. DA, while significant in all three taxa, explains relatively less shape variation than FA does. Facial asymmetry correlates neither with tooth wear asymmetry nor increases with age in a mountain gorilla subsample, undermining the hypothesis that facial asymmetry is driven by chewing side preference. An examination of temporal trends shows that stress-induced developmental instability has increased over the last 100 years in these endangered apes.


Item Type:Article
Uncontrolled Keywords:Asymmetry; Great apes; Geometric morphometrics; Inbreeding, Stress
Subjects:Medical sciences > Biology > Biological anthropology
Medical sciences > Biology > Mammals
ID Code:73955
Deposited On:20 Jul 2022 11:25
Last Modified:03 Aug 2022 07:50

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