Ontogenetic changes in magnitudes of integration in the macaque skull

Abstract

Objectives: Magnitudes of morphological integration may constrain or facilitate craniofacial shape variation. The aim of this study was to analyze how the magnitude of integration in the skull of Macaca fascicularis changes throughout ontogeny in relation to developmental and/or functional modules. Materials and methods: Geometric morphometric methods were used to analyze the magnitude of integration in the macaque cranium and mandible in 80 juvenile and 40 adult M. fascicularis specimens. Integration scores in skull modules were calculated using integration coefficient of variation (ICV) of eigenvalues based on a resampling procedure. Resultant ICV scores between the skull as a whole, and developmental and/or functional modules were compared using Mann-Whitney U tests. Results: Results showed that most skull modules were more tightly integrated than the skull as a whole, with the exception of the chondrocranium in juveniles without canines, the chondrocranium/face complex and the mandibular corpus in adults, and the mandibular ramus in all juveniles. The chondrocranium/face and face/mandibular corpus complexes were more tightly integrated in juveniles than adults, possibly reflecting the influences of early brain growth/development, and the changing functional demands of infant suckling and later masticatory loading. This is also supported by the much higher integration of the mandibular ramus in adults compared with juveniles. Discussion: Magnitudes of integration in skull modules reflect developmental/functional mechanisms in M. fascicularis. However, the relationship between "evolutionary flexibility" and developmental/functional mechanisms was not direct or simple, likely because of the complex morphology, multifunctionality, and various ossification origins of the skull.

Is craniofacial morphology and body composition related by common genes: Comparative analysis of two ethnically diverse populations

“…However, the systematic analysis of the possible genetic relationship between CF morphology and BC is extremely limited and this issue remains mostly unanswered. Moreover, the possible correlation between the CF and BC phenotypes has never been considered from the perspective of morphological integration, despite the fact that this issue generally attracted the attention of many human biologists (Arlegi et al, 2018(Arlegi et al, , 2020Bruner et al, 2017;Farina et al, 2019;Mallard et al, 2017) as well as biologists studying nonhuman primates (Conaway et al, 2018;Joganic et al, 2018;Jung et al, 2021;Neaux, 2017). It was hypothesized, for example, that morphological integration is produced and maintained by complex interactions of multiple pleiotropic genes, which determine the developmental processes (e.g., Cole et al, 2017;Monteiro & Nogueira, 2010).…”

Primate body mass and dietary correlates of tooth root surface area

“…Additionally, some lineage-diet combinations are represented by few specimens and bear further investigation in future research. While force magnitudes experienced by maxillary tooth roots must be identical as loading occurs between the jaws, other factors, such as sinus morphology and force directionality (Dempster et al, 1963), cause splanchnocranium and mandibular corpus morphology to diverge in adulthood (Jung et al, 2021). These differences may independently shape and constrain maxillary tooth root morphology, leading to differences in these patterns relative to those observed or mandibular tooth roots.…”

An effect size for comparing the strength of morphological integration across studies

“…For instance, the degree of integration in a set of phenotypic traits has been estimated using the mean absolute pairwise correlation, the mean squared pairwise correlation (e.g., Cheverud et al 1989;Cane 1993), or summary values based on the eigenvalues of the trait covariance (or correlation) matrix (Hansen & Houle, 2008;Haber, 2011;O'Keefe et al, 2022;Pavlicev et al, 2009;Shirai & Marroig, 2010;Van Valen, 1974;Wagner, 1984). Many studies have successfully deployed these approaches to characterize the extent to which morphological integration is displayed across traits in particular taxa (e.g., Grabowski & Porto 2017;Conaway et al 2018;Machado et al 2019;Jung et al 2020b).…”