DEB Proposal: SG: Collaborative Research: Repeated evolution of limblessness and head-first burrowing in tetrapods: Testing predictions from the fossil record

动物物种已经进化出令人难以置信的身体形状多样性，以反映它们不同的生态和功能，例如，游泳，飞行，挖洞一个有趣的模式是，在亲缘关系较远的动物物种群体中，相似体型的独立进化重复;这被称为趋同进化。体型的趋同是如何以及为什么发生的，这是一个基本的进化难题。这个研究项目探讨了解剖学、生物力学、发育和自然选择压力，这些压力推动了四肢无力和头先穴居的进化。穴居行为和四肢的丧失是趋同进化的经典案例，本项目将测试有关选择压力的一般假设，这些选择压力导致各种蛇，蜥蜴和两栖动物物种具有相似的身体形状。在这个项目中，计算机分析将应用于从医学成像技术产生的头骨形状的图像。这些数据将用于测试化石和活体动物的形式和功能之间的关系。这项工作的结果对于理解进化如何以及为什么反复达到一些常见的穴居生物力学解决方案非常重要。拟议的研究还提供了独特的指导和推广机会。该项目将为来自服务不足社区的学生提供研究经验。它将开发一个移动的工具包，其中包括专门用于科学外联活动的模拟和数字组件，并将通过多种公共外联活动向公众介绍演变过程。该研究项目将测试头先挖洞（HFB）的原因变化，这是趋同进化的一个突出例子。四肢的减少和丧失与使用头部作为穴居工具有关，包括蛇、两栖动物、蜥蜴的多个分支和几个已灭绝的四足动物群。该研究将描述和量化活体HFB物种骨和软组织的形态变异性。将收集显微CT和组织学数据，以评估生物材料组成、缝合模式和远缘相关分类群的发育轨迹。这些结果将被放置在一个系统发育和发展的背景下，使用系统发育比较方法。因此，这项工作将从变异的模式中推断出形式、功能和进化历史。为现存分类群设计的调查框架将被应用于灭绝的，推定的HFB分类群，以提供独立的测试先前的观察化石的假设。这项工作的范围将通过NSF支持的数据库（如Morphobank和Dryad）共享3D解剖模型，系统发育矩阵和标本数据来扩展。

Animal species have evolved an incredible diversity of body shapes to reflect their different ecology and functions, e.g., swimming, flying, burrowing. An intriguing pattern is the independent evolutionary repetition of similar body shapes among distantly related groups of animal species; this is known as convergent evolution. How and why convergence of body shape occurs is a fundamental evolutionary puzzle. This research project examines the anatomical, biomechanical, developmental, and natural selection pressures that drive the evolution of limblessness and head-first burrowing. Burrowing behavior and the loss of limbs is a classic case of convergent evolution, and this project will test general hypotheses concerning the selective pressures that gave give rise to similar body shapes in various snakes, lizard and amphibian species. In this project, computer analysis will be applied to images of skull shape created with technologies derived from medical imaging. That data will then be used to test for relationships between form and function in both fossils and living animals. The results of this work will be important to understanding how and why evolution arrived repeatedly at some common biomechanical solutions for burrowing. The proposed research also provides unique mentoring and outreach opportunities. This project will provide research experience for students from underserved communities. It will develop a mobile toolkit of both analog and digital components devoted to science outreach activities, and it will inform the public about evolutionary processes through multiple public outreach events. The research project will test for variation in the causes of head-first burrowing (HFB) which is a prominent example of convergent evolution. Reduction and loss of limbs is associated with the use of the head as a burrowing tool across snakes, amphibians, multiple clades of lizards, and several extinct tetrapod groups. The research will describe and quantify the morphological variability in bony and soft tissues in living HFB species. Micro CT and histological data will be collected to assess biomaterial composition, suture patterns, and developmental trajectories across distantly-related taxa. Those results will be placed in a phylogenetic and developmental context using phylogenetic comparative methods. The work will thus infer form, function, and evolutionary history from the patterns of variability. The investigative framework devised for extant taxa will then be applied to extinct, putative HFB taxa to provide independent tests of prior observational hypotheses made for fossils. The reach of this work will be extended through data sharing of the 3D anatomical models, phylogenetic matrices, and specimen data via NSF-supported databases such as Morphobank and Dryad.