Chewing on the trees: constraints and adaptation in the evolution of the primate mandible

Chewing on different food types is a demanding biological function. The classic assumption in studying the shape of feeding apparatuses is that animals are what they eat, meaning that adaptation to different food items accounts for most of their interspecific variation. Yet, a growing body of evidence points against this concept. We use the primate mandible as a model structure to investigate the complex interplay between shape, size, diet and phylogeny. We find a weak but significant impact of diet on mandible shape variation in primates as a whole but not in anthropoids and catarrhines as tested in isolation. These clades mainly exhibit allometric shape changes which are unrelated to diet. Diet is an important factor in the diversification of strepsirrhines and platyrrhines and a phylogenetic signal is detected in all primate clades. Peaks in morphological disparity occur during the Oligocene (between 37 and 25 Ma) supporting the notion that an adaptive radiation characterized the evo...咀嚼不同类型的食物是一项具有严苛要求的生物学功能。在研究摄食器官形态的相关研究中，经典假设为‘动物的形态由其食性决定’，换言之，对不同食物的适应性演化是物种间形态差异的主要来源。然而，越来越多的研究证据对这一观点提出了质疑。本研究以灵长类下颌骨作为模型结构，探究形态、大小、食性与系统发育之间的复杂相互作用。研究结果显示，整体而言食性对灵长类下颌骨的形态变异存在微弱但显著的影响，但单独分析类人猿（anthropoids）与狭鼻猴类（catarrhines）时，并未观察到该效应。这两类支系主要表现出与食性无关的异速生长形态变化。食性是原猴亚目（strepsirrhines）与阔鼻猴类（platyrrhines）物种分化的重要影响因素，且所有灵长类支系中均检测到系统发育信号。形态差异的峰值出现在渐新世（3700万至2500万年前），这支持了‘适应性辐射是演化（evo……）的典型特征’这一观点。