Genetic Correlations Among Dental, Mandibular, and Postcranial Dimensions in Rhesus Macaques (Macaca mulatta)

Tooth dimensions typically scale with mandibular and postcranial size in primates, although the exact pattern of scaling varies. This study assesses whether correlations by tissue type, anatomical region, or function (mastication or intrasexual competition) are present and could therefore act as evolutionary constraints on tooth-jaw-body size relationships by estimating genetic and phenotypic correlations between dental, mandibular, and postcranial dimensions in rhesus macaques (Macaca mulatta).

The teeth, mandibles, and postcrania of 362 adults from the Cayo Santiago skeletal collection were measured. Humeral and femoral articular surfaces were selected to represent skeletal elements frequently used to reconstruct primate body size. Genetic correlations were estimated in SOLAR. Random skewers analyses were used to compare genetic and phenotypic correlation matrices to each other and to test matrices.

The genetic correlation matrix was most similar to the test matrix of integration by tissue type (tooth and bone) (r = 0.765, p < 0.001), and nearly as similar to the anatomical region test matrix (r = 0.714, p < 0.001). Hierarchical clustering of the genetic correlation matrix showed similar separation by tissue type. Phenotypic correlation matrices were significantly similar to the genetic correlation matrix (r = 0.813-0.846, p < 0.001) and to most of the test matrices.

Postcanine dental traits were highly heritable but were not closely genetically correlated with mandibular or postcranial dimensions. These findings indicate that scaling relationships between tooth and bone may be maintained in some populations through nongenetic, environmental factors rather than genetic constraints.