Data from: Testing adaptive hypotheses of convergence with functional landscapes: a case study of bone-cracking hypercarnivores

Morphological convergence is a well documented phenomenon in mammals, and adaptive explanations are commonly employed to infer similar functions for convergent characteristics. I present a study that adopts aspects of theoretical morphology and engineering optimization to test hypotheses about adaptive convergent evolution. Bone-cracking ecomorphologies in Carnivora were used as a case study. Previous research has shown that skull deepening and widening are major evolutionary patterns in convergent bone-cracking canids and hyaenids. A simple two-dimensional design space, with skull width-to-length and depth-to-length ratios as variables, was used to examine optimized shapes for two functional properties: mechanical advantage (MA) and strain energy (SE). Functionality of theoretical skull shapes was studied using finite element analysis (FEA) and visualized as functional landscapes. The distribution of actual skull shapes in the landscape showed a convergent trend of plesiomorphically low-MA and moderate-SE skulls evolving towards higher-MA and moderate-SE skulls; this is corroborated by FEA of 13 actual specimens. Nevertheless, regions exist in the landscape where high-MA and lower-SE shapes are not represented by existing species; their vacancy is observed even at higher taxonomic levels. Results highlight the interaction of biomechanical and non-biomechanical factors in constraining general skull dimensions to localized functional optima through evolution.形态趋同（morphological convergence）是哺乳类中已有充分研究记载的现象，学界通常借助适应性解释来推断趋同特征具有相似功能。本研究采纳理论形态学与工程优化的相关思路，用以检验适应性趋同演化的相关假说。本研究以食肉目（Carnivora）中的碎骨生态形态型为案例开展研究。此前研究表明，在趋同演化的碎骨类犬科与鬣狗科动物中，头骨加深与加宽是主要的演化模式。本研究构建了一个简单的二维设计空间，以头骨宽长比与深长比作为变量，探究两种功能属性的最优形态：机械优势（mechanical advantage, MA）与应变能（strain energy, SE）。本研究通过有限元分析（finite element analysis, FEA）对理论头骨形态的功能特性进行探究，并将其可视化为功能景观图。实际头骨形态在功能景观中的分布显示出一种趋同演化趋势：具有原始祖征的低机械优势、中等应变能的头骨，逐渐向高机械优势、中等应变能的头骨演化；这一趋势得到了13件实际标本的有限元分析结果的佐证。然而，功能景观中存在部分区域，现有物种并未占据高机械优势、低应变能的形态，即便在更高的分类阶元层面也未发现此类形态的存在。本研究结果揭示，生物力学与非生物力学因素共同作用，通过演化过程将头骨的整体形态约束在局部功能最优区间内。