Interrelations Between the Cranium, the Mandible and Muscle Architecture in Modern Domestic Dogs
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RESEARCH ARTICLE
Interrelations Between the Cranium, the Mandible and Muscle Architecture in Modern Domestic Dogs Colline Brassard1,2 · Marilaine Merlin1 · Claude Guintard3,4 · Elodie Monchâtre‑Leroy5 · Jacques Barrat5 · Cécile Callou2 · Raphaël Cornette6 · Anthony Herrel1 Received: 17 March 2020 / Accepted: 7 September 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Many studies have attested to the consequences of the recent and intense artificial selection on the morphological variability of the cranium and mandible in domestic animals. However, the functional relations of the cranium with other constituents of the masticatory apparatus (the mandibles and the adductor muscles) have rarely been explored. Previous work has demonstrated strong relationships between the overall shape of the mandible and muscle data, however, drastic artificial selection in dogs has led to frequent malocclusions, suggesting a possible decoupling between the cranium and the mandible. Moreover, the more complex role of the cranium suggests that it is likely less impacted by, and correlated with, the architecture of the jaw muscles than the mandible. We explored the covariations between cranial and mandibular shape and between cranial shape and the masticatory muscle architecture. Shape analyses were conducted on 58 dogs from various breeds and we used muscle data previously obtained from the dissection of 48 of these dogs. The shape of the cranium was quantified using 3D geometric morphometric approaches. Principal component analyses (PCA) and two-block partial least square analyses (2B-PLS) were used to quantify the variations in cranial shape and the covariations with mandible shape and muscle architecture, respectively. Interestingly, our results reveal strong covariations between cranial shape and mandibular shape and between cranial shape and masticatory muscles mass or physiological cross-sectional area, irrespective of whether size is taken into account or not. We conclude that the drastic artificial selection in domestic dogs has not tainted the integrity of the jaw system, which reinforces previous assumptions hypothesising that phenotypic variability in dogs may be limited by developmental factors. Keywords Dog · Skull · Masticatory system · Jaw muscle architecture · Domestication · Geometric morphometrics
Introduction Colline Brassard and Marilaine Merlin are co-first authors. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11692-020-09515-9) contains supplementary material, which is available to authorized users. * Colline Brassard [email protected] 1
UMR 7179 Mécanismes Adaptatifs et Evolution (CNRS, MNHN), Muséum national d’Histoire naturelle, 55 rue Buffon, Paris, France
2
Archéozoologie, archéobotanique : sociétés, pratiques et environnements (AASPE), Muséum national d’Histoire naturelle, CNRS, 57 rue Cuvier, CP5575005 Paris, France
3
Laboratoire d’Anatomie comparée, Ecole Nationale Vétérinaire, de l’Agroalimentair
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