Evolution of Tetrapod Limb Bone Design: Testing the Relationship Between Limb Bone Loads and Locomotion

四足动物肢骨设计的进化：测试骨负荷与运动之间的关系克莱姆森大学四足动物的肢骨在形状上表现出巨大的多样性。长期以来，人们一直认为这些形状差异与动物肢体骨骼在运动过程中所承受的载荷差异密切相关。然而，对使用陆地运动的动物的肢骨负荷和肢骨设计之间关系的研究主要是对特殊哺乳动物和鸟类的研究，在这些物种中观察到的模式可能并不适用于所有脊椎动物。例如，一些两栖动物和爬行动物使用非常规的运动方式，例如青蛙的跳跃和乌龟的缓慢行走。对这些物种如何应对施加在四肢上的负荷的研究将极大地扩展对决定肢骨设计因素的认识。这些研究将为运动负荷与骨形状和骨材料强度之间的关系提供关键的测试。这类研究还将检验在哺乳动物和鸟类身上看到的模式是否是所有脊椎动物进化的原始特征。本项目将通过比较五大脊椎动物（青蛙、蝾螈、海龟、蜥蜴和基础哺乳动物）的肢骨设计和肢骨负荷来解决这些关于肢骨的形式、功能和进化的问题，这些脊椎动物使用不同形式的陆地运动（跳跃、慢走和快跑）。将收集三种主要类型的数据。(1) 9种动物股骨上的力、应力和应变（通过手术植入的应变片和力板数据与肢体运动的高速视频同步评估）。(2)同一物种股骨的力学性能（抗破坏能力）。(3)对各种脊椎动物股骨形状的外部和内部测量。这些研究将提供大多数这些物种的肢体骨负荷的第一次测量。在这个项目中使用的比较方法将在进化的背景下明确地分析肢体力学数据。这是一种新颖的方法，将测试运动方式与肢体骨负荷、形状和机械特性之间的相关性是否代表新的功能适应，而不是原始祖先保留的特征。这些研究将为长期以来关于骨骼和运动进化的观点提供检验，并将推动该领域向四肢骨骼特性的综合进化解释发展。这项工作将加强对几名年轻科学家的培训和机会，包括一名博士后研究员、本科生和研究生，以及两名新教员（其中一名来自专门的本科生机构）。这项工作的结果也将被纳入两所大学的学生教学和提供给当地科学教师的材料中。该项目还将通过检查骨骼对不同环境和机械需求的反应，为临床领域（例如矫形外科）提供数据。最后，通过在进化背景下测试形式和功能之间相关性的假设，本研究将为未来更广泛的功能进化综合研究提供基础。

Evolution of Tetrapod Limb Bone Design: Testing the Relationship Between Bone Loads and LocomotionRichard W. BlobClemson UniversityThe limb bones of tetrapods show enormous diversity in shape. It has long been thought that these shape differences were closely related to differences in loads that animal limb bones have to support during locomotion. However, research on the relationship between limb bone loading and limb bone design in animals that use terrestrial locomotion has been dominated by studies of specialized mammals and birds, and the patterns observed in these species might not be true for all vertebrates. For example, some amphibians and reptiles use unconventional types of locomotion, such as jumping in frogs and slow walking in turtles. Studies of how these species deal with the loads placed on their limbs will dramatically expand knowledge of the factors that determine limb bone design. Such studies will provide critical tests of how the loads of locomotion relate to bone shape and the strength of bone material. Such studies will also test whether patterns seen in mammals and birds are evolutionarily primitive features of all vertebrates.This project will address these questions about the form, function and evolution of limb bones by comparing limb bone design with limb bone loads in species from five major groups of vertebrates (frogs, salamanders, turtles, lizards, and basal mammals) that use different forms of terrestrial locomotion (jumping, slow walking, and fast running). Three main types of data will be collected. (1) Forces, stresses, and strains on the femur in nine species (evaluated from surgically implanted strain gauges and force plate data synchronized with high-speed video of limb movements). (2) Mechanical properties (resistance to failure) of the femur in the same species. (3) External and internal measurements of femur shape from a broad range of vertebrate species. These studies will provide the first measurements of limb bone loads in most of these species. The comparative methods used in this project will explicitly analyze limb mechanics data in an evolutionary context. This is a novel approach that will test whether correlations between locomotor style and limb bone loads, shape, and mechanical properties represent new functional adaptations, rather than traits retained from primitive ancestors. These studies will provide tests of long-standing ideas about evolution of bone and locomotion, and will move the field toward comprehensive evolutionary explanations of limb bone properties.This work will enhance training and opportunities for several young scientists, including a postdoctoral researcher, undergraduate and graduate students, and two new faculty members (one from an exclusively undergraduate institution). Results from this work also will be incorporated into instruction for students at two colleges and into materials provided to local science teachers. This project will also provide data for clinical fields (e.g., orthopedics) by examining how the skeleton responds to varying environments and mechanical demands. Finally, by testing hypotheses about correlations between form and function in an evolutionary context, this research will provide a foundation for a broad range of future integrative studies of functional evolution.