The Interrelation Among Allometry, Phylogeny, and Diet in the Molar Cervix

Abstract

Objectives

Root surface morphology has been used to examine functional signals related to diet and taxonomic affinities in primates with varying degrees of success. The aim of this study is to determine if the use of the functionally significant root cervix can enhance our understanding of these relationships in catarrhines.

Materials and Methods

Two-dimensional (2D) semilandmark points were collected using cross sections taken from the cervix of all three mandibular molar positions in a sample of extant catarrhines (n = 68). Multivariate regression was used to examine the influence of size on Procrustes aligned data. Standard and phylogenetic principal component analyses were performed for each molar position. Phylogenetic generalized least squares (PGLS) were used to correct for nonindependence.

Results

Allometric effects were statistically significant (p < 0.05) but weak for each position (M₁ = 0.096, M₂ = 0.064, M₃ = 0.062). Phylogenetic signal, multivariate K, was significant for each molar but less than expected under Brownian motion (K_mult < 1). PGLS removed all functional signal related to dietary ecology at M₁ for phylogenetically aligned PCA (PACA) and phylogenetic PCA (pPCA) components. These signals were diminished but not eliminated at M₂ (PACA) and M₃ (pPCA).

Conclusions

The influence of size on the morphology of the root cervix is limited and does not impact functional signals related to either phylogeny or diet. Observed morphological variation of the root cervix is driven in part by both phylogeny and diet. However, these variables share a strong relationship, and more work is needed to disentangle the two.