Career: Evolution of Insect Flight

9722196种昆虫约占所有已知物种的三分之二。它们无与伦比的进化成功，以及它们的经济影响，似乎源于它们在三维空间中长距离快速移动的能力，即它们的飞行能力。该提案将研究昆虫是如何进化飞行的。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的。在没有有利的中间阶段证据的情况下，唯一的另一种解释是，某种形式的宏观突变产生了一种能够飞行的动物新星。考虑到飞行依赖于翅膀、神经和肌肉之间极其复杂的相互作用，而这些都不是偶然出现的，这样的解释使人难以相信。因此，关键任务是确定翅膀推进运动的可能中间阶段，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。在石蝇(翼翅目)中已经发现了这样的系统，石蝇是一种原始的昆虫群体，利用翅膀推动的运动来航行或拍打水面。这个项目将构建一个基于DNA的系统发育树(“家谱”)，以确定石蝇的表面掠食、飞行和翅膀结构在它们的进化史上发生了怎样的变化。这个项目的前期工作已经在平面、广播和电视媒体上得到了广泛的宣传，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《科学美国人的前沿》的一集向100多万学童介绍了这项工作，随后与参与其中的科学家举行了电子邮件问答论坛。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就进化之谜提出问题并寻求答案，进化之谜是地球生命历史的核心。

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.