Open AccessFacial asymmetry tracks genetic diversity amongGorillasubspecies
Author(s) -
Kate McGrath,
Amandine B. Eriksen,
Daniel GarcíaMartínez,
Jordi Galbany,
Aida GómezRobles,
Jason Massey,
Lawrence M Fatica,
Halszka Glowacka,
Keely Arbenz-Smith,
Richard Muvunyi,
Tara S. Stoinski,
Michael R. Cranfield,
Kirsten Gilardi,
Chantal Shalukoma,
Emmanuel de Merode,
Emmanuel Gilissen,
Matthew W. Tocheri,
Shan C. McFarlin,
Yann Heuzé
Publication year - 2022
Publication title -
proceedings - royal society. biological sciences/proceedings - royal society. biological sciences
Language(s) - English
Resource type - Journals
eISSN - 1471-2954
pISSN - 0962-8452
DOI - 10.1098/rspb.2021.2564
Subject(s) - fluctuating asymmetry , gorilla , crania , subspecies , facial symmetry , population , asymmetry , biology , hominidae , morphometrics , evolutionary biology , zoology , demography , psychology , anatomy , genetics , biological evolution , physics , social psychology , paleontology , quantum mechanics , sociology
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 threeGorilla 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.