The relationship between tooth morphology and mechanical dietary properties in two Malagasy lemur families (Lemuridae and Indriidae).

摘要

Because the primary role of teeth is to initiate food break down, the basic relationship between teeth and foods is a physical one. Recent work in functional dental morphology has focused on providing a biomechanical basis for correlating tooth form with diets. This study quantified two physical properties of foods, hardness and shear strength, in the diets of lemur taxa (Propithecus diadema edwardsi, Lemur fulvus rufus, L. rubriventer, P. v. verreauxi, L. catta) occupying two sites in Madagascar. Several hypotheses were tested that were derived from relationships hypothesized in the literature or from mechanical considerations of food breakdown: (1) cusp acuity is positively correlated with food hardness, (2) crest length is positively correlated with the strength of foods in shear and (3) occluding cusp to basin ratios decrease with food hardness.;Prior to addressing these hypotheses, data on food properties and tooth measurements were collected. Variation in dietary hardness and shear strength was demonstrated in two seasons of field work. Lemur taxa differed in the most stressful foods eaten and in time spent feeding on foods with particular mechanical values. Hardness ranges for all taxa were similar across seasons, while shear strength values increased in the dry season. Mechanical dietary profiles were established for the five lemur taxa.;Tooth features of the second upper and lower molars of taxa comprising the Lemuridae and Indriidae were measured to examine variation in tooth features in terms of body size and taxonomic affiliation before considering functional relationships. Tooth features scaled isometrically with body size surrogates. Lemurid taxa displayed more variability in tooth features than indriids. The five field taxa demonstrated correlations among tooth features that differed from patterns within their families.;Tooth features and the two physical properties were definitely correlated. Hardness was associated with blunt cusps; deep, acute basins and tight occlusion, strong foods with shallow, flat basins; acute cusps and loose occlusion. Of the hypotheses listed above, only cusp acuity was positively correlated with food hardness. The most stressful foods were more highly correlated with tooth features than frequently eaten foods, although these foods were also correlated with tooth features.