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

动物物种进化出了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。体型趋同是如何以及为什么发生的，这是一个基本的进化难题。本研究项目探讨了解剖学、生物力学、发育和自然选择的压力，这些压力推动了无肢体和头朝下挖洞的进化。挖洞行为和四肢的丧失是趋同进化的一个经典案例，这个项目将测试关于选择压力的一般假设，这种选择压力导致了各种蛇、蜥蜴和两栖动物物种的相似体型。在这个项目中，计算机分析将应用于由医学成像技术产生的头骨形状图像。然后，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是如何以及为什么反复出现一些常见的生物力学解决方案对于挖洞是很重要的。拟议的研究还提供了独特的指导和外展机会。该项目将为来自服务欠缺社区的学生提供研究经验。它将开发一个由模拟和数字组件组成的移动工具包，专门用于科学推广活动，并将通过多个公共推广活动向公众介绍进化过程。该研究项目将测试头先挖洞（HFB）的变异原因，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在蛇、两栖动物、蜥蜴的多个分支和几个已灭绝的四足动物群体中挖洞的工具有关。该研究将描述和量化活HFB物种的骨和软组织的形态学变异。显微CT和组织学数据将被收集，以评估生物材料的组成，缝合模式，和发展轨迹跨越遥远的相关分类群。这些结果将被放置在系统发育和发展的背景下，使用系统发育比较方法。因此，这项工作将从变异性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随后将应用于已灭绝的、假定的HFB分类群，为先前对化石所做的观察假设提供独立的检验。这项工作的范围将通过nsf支持的Morphobank和Dryad等数据库共享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.