Maxillary sinus variation in hybrid macaques: implications for the genetic basis of craniofacial pneumatization

Abstract

There has been a long‐standing debate regarding the diversification of paranasal sinuses, namely pneumatized spaces in the face. Functional adaptation and structural constraints have generally been suggested to explain sinus diversification in vertebrates. Here we investigated variation in the maxillary sinus and the external facial cranium in hybrid Taiwanese–Japanese macaques to estimate the genetic basis of phenotypic differences. The Taiwanese macaques have a large sinus, whereas the Japanese macaques have a small sinus; they are also significantly different in their external craniofacial morphology. Variations in the hybrids' external craniofacial morphology can be mostly explained by a simple additive model. In contrast, their sinus morphology significantly deviates from the value expected under this additive model, wherein most hybrids have a large sinus, similar to that in Taiwanese macaques, regardless of the degree of hybridization. When the whole structure is considered, a novel phenotype can be seen in the hybrids. Our results suggest that the sinus and face are independent of each other, both genetically and developmentally, and that the small sinus is mainly caused by intrinsic genetic factors, rather than being structurally constrained by the craniofacial architecture. Such genetic factors may have contributed to the enigmatic diversity of craniofacial pneumatization. © 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 115, 333–347.

Zygomaticomaxillary Morphology and Maxillary Sinus Form and Function: How Spatial Constraints Influence Pneumatization Patterns among Modern Humans

“…The results of this study further contribute to a growing body of literature demonstrating strong morphological relationships between external and internal craniofacial structures (Koppe et al, b; Koppe et al, ; Zollikofer et al, , Ito et al, ; but see Ito et al, ). Specifically, and in agreement with our previous study (Butaric and Maddux, ), our current results demonstrate significant morphological covariation between the size and shape of the maxillary sinus and the surrounding midfacial skeleton.…”

“…As a consequence, the hypotheses presented here should not be taken as suggesting that sinuses initially evolved to facilitate a structural function, or that sinuses may not have been co‐opted for alternative functions in other lineages (Witmer, ; Rae, ). Additionally, in certain lineages, such as macaques, sinus morphology may simply be related to stochastic rather than either structural or physiological function (Ito et al, ). That being said, the results of our study primarily point to the need to better understand morphological relationships between the maxillary sinus and midfacial skeleton during human growth and development.…”

Biological relationships and frontal sinus similarity in skeletal remains with known genealogical data

“…The question of the influence of frontal sinus pattern inheritance, its informative value, and methodology is still under discussion (Latiff et al ., 2009; Ito et al ., 2015). All of the above‐mentioned studies dealing with frontal sinus and relatedness assume that genetics affects frontal sinus dimensions and morphology.…”

Morphological Covariation between the Maxillary Sinus and Midfacial Skeleton among Sub‐Saharan and Circumpolar Modern Humans

“… It is important to note that there are vast differences in the degree of maxillary sinus pneumatization among macaque species (Koppe and Ohkawa, ; Ito et al, ), and that additional factors likely contribute to these scaling patterns (Koppe and Nagai, ; Koppe et al, ).…”