Sun, Nov 16, 2003 page9

• Flies key to evolution study

  A major study of man's constant companion could have important implications for the development of evolutionary theory

  • THE OBSERVER
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  Flies have been around for at least 250 million years, surviving global warming and freezing and major "extinction events" such as that which wiped out the dinosaurs. Yet we know surprisingly little about this constant and frequently irritating companion to man and animal life.

  In an attempt to rectify this, Australian scientists have joined a global effort to map the genetic structure and evolutionary history of the fly which could also entail a major rethink of Darwinian principles. One of them, David Yeates, an entomologist, describes the task as "an incredibly important project considering flies comprise about 10 percent of animal life forms on the planet."

  Yeates and John Oakshott, a molecular biologist, are directing a US$2.4 million grant from America's National Science Foundation for Australian participation in the study, which also includes US, Canadian and Singaporean teams. Their job is to bring together field research in the coming fly-ridden Australian summer and recover the fossil records going back millions of years of flies preserved in amber, shale and ancient layers of marine sediments.

  

  ILLUSTRATION: MOUNTAIN PEOPLE

  "It is difficult but not impossible to recover data from flies that have been dead for a few hundred million years," Yeates says.

  "In some cases, they left behind hard casings or exo-skeletal remains, and in others we even see internal organs containing traces of DNA. With very well preserved flies or those we catch alive, electron microscopy is yielding detail that would have eluded scrutiny until recent advances in medical or forensic technology," he says.

  A favorite saying of Yeates is that "a big part of biodiversity is actually `flyodiversity.' Of nearly 2 million living species known to science, and with many more yet to be identified, around one-tenth are flies or `diptera' of some sort," he adds.

  Diptera, a large order of insects having a single pair of wings and a sucking or piercing mouthpart, includes flies, mosquitoes, gnats and midges.

  Yeates estimates there are up to 40,000 distinct species of flies in Australia alone, although only 8,000 of them have been scientifically described and named. When the five-year international project is completed it expects to have grouped between 200,000 to 400,000 types of flies into at least 150 distinct families.

  "There are major practical implications from knowing our flies better," Yeates says. "They have been around for at least 250 million years, appearing well before the dinosaurs and surviving periods of global warming, global freezing and major extinction events that saw many species, including the dinosaurs, cut down at the seeming height of their powers. So we know that by studying their genetic make-up we may learn more about their capacity to adapt to shocks that destroyed other life forms."

  But the benefit of mapping fly DNA goes much further, because the fly genome has enough in common with the human genome to help decode the more complex genetic makeup of mankind. Being simpler, it is also much better understood in species like the common brown fly found everywhere except in the most extreme southern polar environments.

  "When we see something unknown in the human genome we can often get clues to its purpose by computer matching a similar genetic structure in a type of fly where that particular molecular combination already has a known function," Yeates says.

  Oakshott's major role in the project is to examine the genes that are making some modern flies resistant to the pesticides used in agriculture. Finding out whether those genes have lain dormant for aeons before being "turned on" by a dose of fly spray, or evolved as an instantaneous defense mechanism in flies in the last 100 years is one of the biggest riddles in the study of evolution.

  "This is a crucial question because it is asked of all species of animal," Yeates says. "If we discover that the environmental stresses caused by the rise of humans can cause the instantaneous origination of new species of flies then a lot of things that are accepted about evolution will need revision."

  Already the world's farms -- where pesticide-resistant flies are breeding better than those that didn't adapt -- are looking like a case study from journals of the 19th century naturalist Charles Darwin, who first described the evolution of species as a coherent scientific theory.

  The Australian part of the fly study will be incorporated in a National Science Foundation "Tree of Life" electronic databank and a web site run by the US Department of Agriculture in Washington.

  "This is where the continuing practical benefits of the work will become apparent," Yeates says. "It means there will be an open source of information available for use by agricultural or medical researchers, where the answers to their questions may have been buzzing around their heads without being recognized."
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