Data from: Lower jaw modularity in the African Clawed Frog (Xenopus laevis) and Fire Salamander (Salamandra salamandra gigliolii)

Modularity describes the degree to which the components of complex phenotypes vary semi-autonomously due to developmental, genetic, and functional correlations. This is a key feature underlying the potential for evolvability, as it can allow individual components to respond to different selective pressures semi-independently. The vertebrate lower jaw has become a model anatomical system for understanding modularity, but to date, most of this work has focused on the mandible of mammals and other amniotes. In contrast, modularity in the mandible of lissamphibians has been less well-studied. Here, we used geometric morphometrics to quantify the static (intraspecific) modularity patterns in Xenopus laevis and Salamandra salamandra gigliolii. We tested developmental and functional hypotheses of modularity and demonstrate that both species exhibit significant modularity. Functional modularity was supported in Xenopus, yet the lack of definitive support for both the developmental and functional hypotheses in Salamandra suggests influences on modularity are much more complex. Allometry has a small yet significant impact on lower jaw shape in both taxa and sex has a significant effect on shape in Xenopus. The high modularity seen in both species mimics the results of other studies on the amphibian cranium, suggesting that modularity is a ubiquitous feature of the tetrapod jaw.

模块化（Modularity）指复杂表型的各组分因发育、遗传与功能相关性而呈现半自主变异的程度。这是进化可演化性潜能的核心特征之一，因其可使单个组分半独立地响应不同选择压力。脊椎动物下颌已成为理解模块化的模式解剖系统，但迄今为止，相关研究大多聚焦于哺乳动物及其他羊膜动物的下颌骨。与之相对，滑体两栖类下颌骨的模块化研究则相对匮乏。本研究借助几何形态测量法（Geometric Morphometrics）量化了非洲爪蟾（Xenopus laevis）与火蝾螈吉廖利亚种（Salamandra salamandra gigliolii）的静态（种内）模块化模式。我们检验了模块化的发育假说与功能假说，结果证实两种类群均存在显著的模块化特征。非洲爪蟾的功能模块化假说得到支持，但火蝾螈吉廖利亚种既未明确支持发育假说也未支持功能假说，这表明其模块化的影响机制更为复杂。异速生长（Allometry）对两类群的下颌形态均存在微小但显著的影响，而性别对非洲爪蟾的下颌形态具有显著效应。两种类群所展现的高模块化特征与其他两栖动物颅骨相关研究结果一致，表明模块化是四足动物下颌的普遍特征。