Career: Evolution of Insect Flight

昆虫大约占所有已知物种的三分之二。它们在进化上取得的无与伦比的成功，以及它们对经济的影响，似乎都源于它们在三维空间中远距离快速移动的能力，即它们的飞行能力。这个提案将研究昆虫的飞行是如何进化的。进化生物学的主要挑战之一是确定复杂的特征，如飞行，是如何通过一系列中间阶段进化而来的。没有证据表明有利的中间阶段，唯一的解释是某种形式的大突变产生了具有飞行能力的新生动物。这样的解释让人难以相信，因为飞行依赖于翅膀、神经和肌肉之间极其复杂的相互作用，而这些作用不可能是偶然产生的。因此，关键任务是确定可能的翅膀推进运动的中间阶段，这些阶段服务于有益的目的，并为渐进的自然选择提供机会。这种系统已经在石蝇（翼翅目）中被发现，石蝇是一种原始的昆虫，它们利用翅膀推动运动在水面上航行或拍打。这个项目将构建一个基于DNA的系统发育（一个“家谱”）来确定石蝇的表面掠食、飞行和翅膀结构在它们的进化史上是如何变化的。该项目的初步工作已在印刷、广播和电视媒体上广泛宣传，因为它的意义和影响很容易为公众所理解。公共电视连续剧《科学美国人前沿》（Scientific American Frontiers）的一集向100多万名学生展示了这项工作，随后是一个由参与其中的科学家组成的电子邮件问答论坛。正在进行的工作将继续提供一个非常明显的例子，说明现代生物学家如何提出问题并寻求关于地球生命历史中心的进化之谜的答案。

Marden 9722196 Insects constitute roughly two thirds of all known species. Their unparalleled evolutionary success, as well as their economic impact, appears to derive from their ability to move rapidly over large distances in three dimensional space, i.e. their ability to fly. This proposal will investigate how flight evolved in insects. One of the primary challenges for evolutionary biology is to determine how complex traits, such as flight, evolved through a series of intermediate stages. Without evidence for advantageous intermediate stages, the only alternative explanation is that some form of macro-mutation produced a flight-capable animal de nova. Such an explanation strains credulity given that flight depends on an exceedingly complex interplay of wings, nerves, and muscles that simply could not arise by chance. Thus, the critical task is to identify possible intermediate stages of wing-propelled locomotion that serve a beneficial purpose and present an opportunity for progressive natural selection. Such a system has been identified in stoneflies (Plecoptera), a primitive group of insects that use wing propelled locomotion to sail or flap their way across water surfaces. This project will construct a DNA based phylogeny (a "family tree") to determine how surface skimming, flight, and wing structure in stoneflies has changed over their evolutionary history. Preliminary work on this project has been widely publicized in print, radio, and television media, as its significance and implications are readily grasped by the general public. An episode of the public television series, Scientific American Frontiers, presented this work to an audience of over 1 million school children, followed by an email question/answer forum with the scientists involved. The ongoing work will continue to provide a highly visible example of how modern biologists ask questions and seek answers regarding evolutionary riddles that are central to the history of life on earth.