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Tip
Sheet: Science & Technology Tip sheets highlight timely news and events at Washington University in St. Louis. For more information on any of the stories below or for assistance in arranging interviews, please see the contact information listed with each story. For comments on the Science & Technology news tips service, please contact the editor, Tony Fitzpatrick at (314) 935-5272 or tony_fitzpatrick@aismail.wustl.edu. Walking sticks regained flight after 50 million years of winglessness Media assistance: Tony Fitzpatrick - (314) 935-5272 Source: Alan Templeton's Laboratory Source: Washington University Department of Biology in Arts & Sciences [St. Louis, Mo., February, 2003] - (This study appeared in Nature on Jan. 16, 2003) An evolutionary genetics graduate student at Washington University in St. Louis is part of a research team that shows a certain group of insects illustrate a spin of an ancient adage: if at first you don't succeed, fly, fly again.
Such a conclusion means that the theory of evolution itself must continue to change. "For entomologists, acquiring wings and the ability to fly was only thought to have occurred once in insect evolution," said Maxwell, who performed the bulk of the DNA sequencing for the study courtesy of National Science Foundation funding as an undergraduate at Brigham Young University. " Our results infer at least one, if not more, reoccurrences of flight after it had been lost. "For evolutionary biology, this represents multiple gains of a complex character, presumably controlled by many genes and developmental processes. For developmental biologists and those studying insect flight, we have now presented them with a set of study organisms that may lead them to a greater understanding of evolutionary developmental processes and the molecular mechanics of flight." Integrative biology professor Michael F. Whiting, Ph.D., of Brigham Young University, led the research team. Their findings, reported in the cover article in the Jan. 16, 2003, edition of "Nature," showed that some species of walking sticks without wings existed before their winged descendants, the first time any organism has been shown to do what scientists previously thought impossible -- re-evolve a complex trait. "For complex functions like flight or sight, the idea in evolution has always been that organisms either use it or lose it," said Whiting, referring to Dollop's Law, which, as cited in the "Encyclopedia of Evolution" is "the principle that organs or complex structures cannot return to a condition seen in an ancestor." "This is the first example of a complex feature being lost and recovered much later in an evolutionary lineage" Whiting said. "Even though the wing is not physically there, the underlying genetics which construct wings appear to be conserved over evolutionary time. It suggests that complexity can be maintained over tens of millions of years." Entomologists have frequently documented cases where species of insects have lost the ability to fly. For example, many insect species that migrate to islands eventually lose wings as an adaptation to keep them from blowing into the sea. Bugs that live on snow don't have wings, and therefore have less surface area and lose less heat.
"At least 50 million years later, for some reason, it was to their advantage to have some of the species become winged again," Whiting said, noting that various species of winged and wingless walking sticks now exist. "The remarkable thing was that they had the ability to generate wings when they needed them." Whiting believes the instructions for growing wings are related to the instructions for making legs and can be turned on and off over long periods of time. The new study means evolutionary lineages can be more adaptive than previously thought, with the ability to move back and forth from a winged or wingless state. He expects future studies to show similar results in cockroaches and other insects, and possibly even in other classes of animals. The walking stick project began when Whiting, an entomologist with a $1.34 million grant from NSF to construct the family tree of the insect class, asked Taylor Maxwell, then a Brigham Young undergraduate, to sequence and analyze the DNA of several species of walking sticks as part of the broader study. Maxwell, supported by grants from the Brigham Young University administration and the NSF designed to facilitate undergraduates' participation in research, put together preliminary results. "As a pre-med major, I was barely learning that there were these fields of research out there," said Maxwell, a study co-author. "Dr. Whiting is very good at introducing people to science and very good at training people in the lab. Fortunately, the results we came up with were very strong with well-supported data." After Maxwell's initial effort, Whiting embarked on a global scavenger hunt, seeking key species of walking sticks thought by experts to be the most primitive, which would help flesh out the study. He brought back samples from Australia, New Guinea and Chile with the aid of Sven Bradler, a graduate student at George August Universitat in Gottingen, Germany, and the study's other co-author. Maxwell is now applying the concepts and techniques he learned in Whiting's lab to his current research into genetic issues related to cancer drugs as an NSF Predoctoral Fellow in a doctoral program at Washington University, a position he believes he earned in large part because of his undergraduate research experience. "When I started this project, I just wanted to get some research experience that would help me get into graduate school," Maxwell said. "I never thought I would end up co-authoring a paper in Nature." |
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