Interrelations Between the Cranium, the Mandible and Muscle Architecture in Modern Domestic Dogs

Brassard, Colline; Merlin, Marilaine; Guintard, Claude; Monchâtre-Leroy, Élodie; Barrat, J; Callou, Cécile; Cornette, Raphäel; Herrel, Anthony

doi:10.1007/s11692-020-09515-9

Cited by 11 publications

(8 citation statements)

References 67 publications

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“…The coefficients of covariation between muscle mass and shape were more elevated for the cranium than for the mandible. The same observation has previously been made for dogs and strepsirrhines (Brassard et al, 2020c;Fabre et al, 2018). This supports the hypothesis that, in foxes, the cranium presents a lesser degree of functional plasticity compared with the mandible, probably because it has to cope with additional functional demands, such as the protection of the sensory systems and brain (Fabre et al, 2014;Figueirido et al, 2011).…”

Section: Relationship Between Muscles and Estimated Bite Forcesupporting

confidence: 87%

Masticatory system integration in a commensal canid: interrelationships between bones, muscles and bite force in the red fox

Brassard

Merlin

Monchâtre-Leroy

et al. 2021

Journal of Experimental Biology

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The jaw system in canids is essential for defence and prey acquisition. However, how it varies in wild species in comparison with domestic species remains poorly understood, yet is of interest in terms of understanding the impact of artificial selection. Here, we explored the variability and interrelationships between the upper and lower jaws, muscle architecture and bite force in the red fox (Vulpes vulpes). We performed dissections and used 3D geometric morphometric approaches to quantify jaw shape in 68 foxes. We used a static lever model and bite force estimates were compared with in vivo measurements of 10 silver foxes. Our results show strong relationships exist between cranial and mandible shape, and between cranial or mandible shape on the one hand and muscles or estimated bite force on the other hand, confirming the strong integration of the bony and muscular components of the jaw system. These strong relationships are strongly driven by size. The functional links between shape and estimated bite force are stronger for the mandible, which probably reflects its greater specialisation towards biting. We then compared our results with data previously obtained for dogs (Canis lupus familiaris) to investigate the effect of domestication. Foxes and dogs differ in skull shape and muscle physiological cross-sectional area (PCSA). They show a similar amount of morphological variation in muscle PCSA, but foxes show lower variation in cranial and mandible shape. Interestingly, the patterns of covariation are not stronger in foxes than in dogs, suggesting that domestication did not lead to a disruption of the functional links of the jaw system.

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Section: Relationship Between Muscles and Estimated Bite Forcesupporting

confidence: 87%

Masticatory system integration in a commensal canid: interrelationships between bones, muscles and bite force in the red fox

Brassard

Merlin

Monchâtre-Leroy

et al. 2021

Journal of Experimental Biology

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“…2020; Brassard et al. 2020). In general, modularity patterns are conserved between dogs and wolves, echoing the results of broader comparisons across mammals (Porto et al.…”

Section: Figurementioning

confidence: 99%

Modularity patterns in mammalian domestication: Assessing developmental hypotheses for diversification

et al. 2021

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The neural crest hypothesis posits that selection for tameness resulted in mild alterations to neural crest cells during embryonic development, which directly or indirectly caused the appearance of traits associated with the “domestication syndrome” (DS). Although representing an appealing unitary explanation for the generation of domestic phenotypes, support for this hypothesis from morphological data and for the validity of the DS remains a topic of debate. This study used the frameworks of morphological integration and modularity to assess patterns that concern the embryonic origin of the skull and issues around the neural crest hypothesis. Geometric morphometric landmarks were used to quantify cranial trait interactions between six pairs of wild and domestic mammals, comprising representatives that express between five and 17 of the traits included in the DS, and examples from each of the pathways by which animals entered into relationships with humans. We predicted the presence of neural crest vs mesoderm modular structure to the cranium, and that elements in the neural crest module would show lower magnitudes of integration and higher disparity in domestic forms compared to wild forms. Our findings support modular structuring based on tissue origin (neural crest, mesoderm) modules, along with low module integration magnitudes for neural crest cell derived cranial elements, suggesting differential capacity for evolutionary response among those elements. Covariation between the neural crest and mesoderm modules accounted for major components of shape variation for most domestic/wild pairs. Contra to our predictions, however, we find domesticates share similar integration magnitudes to their wild progenitors, indicating that higher disparity in domesticates is not associated with magnitude changes to integration among either neural crest or mesoderm derived elements. Differences in integration magnitude among neural crest and mesoderm elements across species suggest that developmental evolution preserves a framework that promotes flexibility under the selection regimes of domestication.

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“…Our analyses clearly demonstrated that the morphological diversity in the head (the mandible being a proxy of overall head shape [37]) of European dogs was considerable well before the Bronze Age, yet lower than in modern dogs. In ancient dogs, mandible size varied from very small, similar to some modern small dogs such as the pomeranian or dachshund, to larger sizes compatible with modern large dogs such as the husky, golden retriever or German shepherd.…”

Section: Discussionmentioning

confidence: 95%

“…Thus, to date, there is no large-scale study describing the morphological variability of European prehistoric dogs. Given the considerable number of mandibles in archaeological assemblages, and the fact that mandibular shape has been proven to be a good indicator of cranial shape and thus of the overall head morphotype in modern dogs [37], this bone is a promising object to explore morphological variability in the head of ancient dogs (yet not systematically correlated to the morphology of the complete body in modern dogs). Additionally, as significant and strong relationships between the mandible and the masticatory muscles have been demonstrated in modern dogs [37,38], mandible form may be used to make functional inferences on archaeological specimens.…”

Section: Introductionmentioning

confidence: 99%

Unexpected morphological diversity in ancient dogs compared to modern relatives

et al. 2022

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Dogs are among the most variable species today, but little is known about the morphological variability in the early phases of their history. The Neolithic transition to farming may have resulted in an early morphological diversification as a result of changes in the anthropic environment or intentional selection on specific morphologies. Here, we describe the variability and modularity in mandible form by comparing 525 dog mandibles from European archaeological sites ranging from 8100 to 3000 cal. BC to a reference sample of modern dogs, wolves, and dingoes. We use three-dimensional geometric morphometrics to quantify the form of complete and fragmented mandibles. We demonstrate that an important morphological variability already existed before the Bronze Age in Europe, yet the largest, smallest, most brachycephalic or dolichocephalic extant dogs have no equivalent in the archaeological sample, resulting in a lower variation compared to modern relatives. The covariation between the anterior and posterior parts of the mandible is lower in archaeological dogs, suggesting a low degree of intentional human selection in early periods. The mandible of modern and ancient dogs differs in functionally important areas, possibly reflecting differences in diet, competition, or the implication of ancient dogs in hunting or defence.

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Interrelations Between the Cranium, the Mandible and Muscle Architecture in Modern Domestic Dogs

Cited by 11 publications

References 67 publications

Masticatory system integration in a commensal canid: interrelationships between bones, muscles and bite force in the red fox

Masticatory system integration in a commensal canid: interrelationships between bones, muscles and bite force in the red fox

Modularity patterns in mammalian domestication: Assessing developmental hypotheses for diversification

Unexpected morphological diversity in ancient dogs compared to modern relatives

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