GENEVA, N.Y. -- For apple maggots, the dating scene is simple -- flies only mate on a specific host fruit. Using new technology developed at the New York State Agricultural Experiment Station, Cornell University researchers have demonstrated that this fact of fly life has resulted in the emergence of two distinct races of the pest in just 150 years.

In research published in the Online Early Edition of the Proceedings of the National Academy of Sciences Web site Sept. 22, the scientists show that one mechanism by which these flies find their host plant is a preference for specific blends of fruit odors. The preference is both strong enough and sensitive enough that the two races of maggot no longer interbreed, the first step in the evolution of a new species. The discovery, the researchers say, opens up a possible new area of organic pest control.

The researchers at the Geneva Experiment Station, part of the College of Agriculture and Life Sciences at Cornell, Ithaca, N.Y., are Charles Linn, Satoshi Nojima and Wendell Roelofs. Their collaborators are Jeffrey Feder from the University of Notre Dame and Stewart Berlocher from the University of Illinois.

Evolutionary biologists theorize that two populations of a species must be isolated from each other if they are to develop into two distinct species, and Darwin provided the example of one species of bird diverging and becoming reproductively isolated on separate islands in the Galapagos. Recently it has been proposed that the separation need not be geographic or even physical. A shift in the use of a new host plant for mating and the laying of eggs could be enough to keep insects that occupy the same area at the same time from mating. This process is termed "sympatric speciation," and that is what the researchers believe has happened with hawthorn maggots.

The apple and hawthorn maggots are common names for the same species, Rhagoletis pomonella . The pest and the hawthorn plant ar
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Contact: Linda McCandless
llm3@cornell.edu
315-787-2417
Cornell University News Service
22-Sep-2003

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