Variation in dental morphology and dietary breadth in primates and their kin

Abstract

Sympatric animals may consume diets of differing breadths as a strategy to reduce competition. Studying patterns of dietary breadth in extinct taxa is difficult because available data are generally limited to morphology. Dental topographic analysis (DTA) is useful for comparing occlusal morphology and allows for examination of dietary adaptations in extinct taxa. What remains unknown is how dental morphology, quantified using DTA, covaries with dietary breadth. The niche variation hypothesis (NVH) posits that taxa with broader ecological niches will be characterized by greater variability in morphology relative to specialized taxa. Therefore, we predict that taxa with greater dietary breadth will have more varied dental morphology compared to specialists as a result of the molar morphology of specialists being under greater genetic control relative to generalists, with specialists requiring teeth specially adapted to efficiently process a smaller range of food sources. We measured curvature, complexity, and relief of the M2 of 3 pairs of closely related euarchontan mammals (primates and treeshrews), with each taxon within a pair categorized as a generalist or specialist. Our results indicate that generalists do not consistently show greater variability in dental morphology compared to specialists among primates, but that atelids and treeshrews do generally follow the predictions of the NVH, with the caveat that our treeshrew sample is small. This suggests that while dietary specialists may be under greater genetic constraint with respect to their molar topography, a link between dietary breadth and dental form is not clear. Our study demonstrates that variation in dental topography does not necessarily reflect dietary breadth and highlights the fact that it is difficult to categorize even the most specialized primates (i.e. bamboo lemurs) as “dietary specialists.”