Data from: Bite of the cats: relationships between functional integration and mechanical performance as revealed by mandible geometry

Cat-like carnivorous mammals represent a relatively homogeneous group of species whose morphology appears constrained by exclusive adaptations for meat eating. We present the most comprehensive dataset of extant and extinct cat-like species to test for evolutionary transformations in size, shape and mechanical performance, i.e. von Mises stress and surface traction, of the mandible. Size and shape were both quantified by means of Geometric Morphometrics while mechanical performance was assessed applying Finite Element Models to two dimensional geometry of the mandible. Additionally, we present the first almost complete composite phylogeny of cat-like carnivorans for which well-preserved fossil mandibles are known, including representatives of 35 extant and 59 extinct species of Felidae, Nimravidae and Barbourofelidae. This phylogeny was used to test morphological differentiation, allometry, and covariation of mandible parts within and among clades. After taking phylogeny into account, we found that both allometry and mechanical variables exhibit a significant impact on mandible shape. We also tested if mechanical performance was linked to morphological integration. Mechanical stress at the coronoid process is higher in sabertoothed cats than in any other clade. This is strongly related to the high degree of covariation within modules of sabertooths mandibles. We found significant correlation between integration at the clade level and per-clade averaged stress values, on both original data and by partialling out interclade allometry from shapes when calculating integration. This suggests a strong interaction between natural selection and the evolution of developmental and functional modules at the clade level.

猫形食肉哺乳动物是一类相对同质化的物种类群，其形态因专性食肉的适应性演化而受到约束。本研究构建了目前最为全面的猫形物种类群数据集（涵盖现生与灭绝类群），用于探究下颌骨（mandible）的尺寸、形态及力学性能（即冯·米塞斯应力（von Mises stress）与表面牵引力（surface traction））的演化变化。本研究通过几何形态测量学（Geometric Morphometrics）量化物种的尺寸与形态，并基于下颌骨的二维几何结构，利用有限元模型（Finite Element Models）评估其力学性能。此外，本研究构建了首个近乎完整的猫型食肉类复合系统发育树，该类群均保留有保存完好的化石下颌骨，涵盖猫科（Felidae）、猎猫科（Nimravidae）与巴博剑齿虎科（Barbourofelidae）的35个现生物种与59个灭绝物种代表类群。借助该系统发育树，本研究检验了支系内部及支系间下颌骨各部分的形态分化、异速生长（allometry）与协变关系。在纳入系统发育效应进行校正后，本研究发现异速生长与力学变量均对下颌骨形态具有显著影响。本研究同时检验了力学性能是否与形态整合（morphological integration）相关联。剑齿虎类（sabertoothed cats）下颌骨冠状突（coronoid process）处的机械应力高于其他所有支系，这与剑齿虎类下颌骨各功能模块内部极高的协变程度密切相关。无论是基于原始数据，还是在计算整合度时通过偏分析去除支系间异速生长对形态的影响后，本研究均发现支系水平的形态整合度与各支系平均应力值之间存在显著相关性。这表明在支系水平上，自然选择与发育及功能模块的演化之间存在强烈的相互作用。