From forests to savannas: Evidence of mandibular shape adaptation in Neotropical monkeys

<p>This repository contains the complete dataset and R scripts necessary to reproduce all analyses and figures presented in the article:</p> <p>Chuma, L.L., Cerezer, F.O., & Cáceres, N.C. (2025). <strong>From forests to savannas: Evidence of mandibular shape adaptation in Neotropical monkeys</strong>. In submission</p> <hr> <h3><strong>Abstract</strong></h3><p>Mandibular shape in primates can reflect more than just dietary function; it could carry signals of ecological adaptations and evolutionary constraint, often overlapping in complex ways. In this study, we investigated mandibular variation in robust Capuchin monkeys (<em>Sapajus</em> spp.) across contrasting South American biomes, ranging from humid forests to dry, seasonal savannas, which provide distinct resource availability. Through geometric morphometrics analyses and accounting for shared ancestry, we tested how shape is structured by different predictors. Our results revealed a strong and consistent allometric relationship shaping mandibular form, shared across different biomes. However, shape differences after correcting for allometry became even clearer, highlighting not only a divergence across distinct biomes (forest vs. savanna) but also a convergence under similar environmental pressure (within savanna). Furthermore, monkeys inhabiting dry and seasonal areas tend to show relatively shorter and more robust mandibles, consistent with functional adaptations to fallback foods. Climatic variables, particularly those linked to precipitation and thermal seasonality, were significantly associated with mandible size variation. Phylogenetic signals, in contrast, are weak and often nonsignificant, suggesting that environmental pressures are more important than shared ancestry in this group.</p> <hr> <h3><strong>Contents</strong></h3><ul> <li><strong>/data:</strong> Contains raw landmark data (.tps), phylogenetic tree (.tre), and metadata files (.csv) for climate and specimen information.</li> <li><strong>/R:</strong> Contains all R scripts, numbered for sequential execution, to perform data processing, geometric morphometric analyses, phylogenetic comparative methods, and figure generation.</li></ul>