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.
