Evolution of modern amphibians

了解现代两栖动物（青蛙，蝾螈和无肢的无足目）的进化历史，目前正在经历世界范围内的数量急剧下降，提供了对我们生态系统的重要组成部分的生存和多样化的重要因素的洞察力。现代两栖动物的进化起源问题是脊椎动物学中数百年来最令人头疼的问题之一。每一个现存群体的高度特化的头骨与化石两栖动物的解剖结构有很大的不同，化石记录中的巨大空白意味着保存中间解剖结构的化石不存在，使关系的重建变得复杂。由于运动行为和小型化的相似性，共同祖先的证据也被过度印刷。我实验室最近的研究已经在青蛙和蝾螈与一个特定的两栖动物化石群之间建立了密切的联系，这使我的研究能够集中在两个后续问题上：导致青蛙和蝾螈的进化变化的机制，以及无尾目起源的性质。申请的发现补助金将支持从多种不同途径研究这些问题。工作将继续记录解剖的braincase，保留证据的共同祖先独立的功能收敛，现代和化石两栖动物使用微CT成像。我们将使用同步加速器扫描来研究广义蝾螈头骨形状的变化，然后将其与直接发育或未能变形的蝾螈进行比较，以了解更多与不同生活史相关的机制。一组穴居两栖动物化石将被详细研究，以了解头先运动如何影响形态，以更好地了解共同祖先的证据被功能覆盖的限制。通过这些研究揭示的新数据将被纳入一项大规模的进化关系研究，首次在两栖动物研究中结合形态学和分子数据。

Understanding the evolutionary history of modern amphibians (frogs, salamanders, and the limbless caecilians), which are currently undergoing drastic worldwide declines in numbers, provides insight into factors important to the survival and diversification of an important part of our ecosystem. The evolutionary origin of modern amphibians has been one of the more vexing problems in vertebrate zoology for hundreds of years. The highly specialized skulls of each of the living groups differ greatly with the anatomy of fossil amphibians, and large gaps in the fossil record mean fossils preserving intermediary anatomy are absent, complicating the reconstruction of relationships. Evidence for common ancestry is additionally overprinted by similarities due to locomotor behavior and miniaturization. Recent research in my laboratory has established a close link between frogs and salamanders and one particular group of fossil amphibians, which enables my research to focus on two subsequent questions: the mechanisms of this evolutionary change leading to frogs and salamanders, and the nature of caecilian origins. The requested Discovery Grant will support research into these problems from a number of different approaches. Work will continue to document the anatomy of the braincase, which preserves evidence of common ancestry independent of functional convergence, of modern and fossil amphibians using micro-CT imaging. We will use synchrotron scanning to study the change in shape of the skull of a generalized salamander and then compare this with salamanders that directly develop or fail to metamorphose to learn more about the mechanisms associated with different life histories. A group of burrowing fossil amphibians will be studied in detail to understand how head first locomotion can affect morphology, to better understand the limits to which the evidence for common ancestry is overwritten by function. New data revealed through these studies will be incorporated into a large-scale study of evolutionary relationships, combining morphological and molecular data for the first time in a study of amphibians.