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Rapid Size Change In Introduced Fruit Fly Indicates It Is Evolving As It Invades North America

Date:
January 17, 2000
Source:
University Of Washington
Summary:
Until now, biologists have not seriously considered evolution as part of the strategy used by invading species. But new evidence stemming from the accidental introduction into North and South America of an Old World fruit fly, which has exhibited one of fastest evolutionary changes ever recorded, may alter that perception.
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The world is filled with examples of introduced exotic species such as African walking fish in Florida, rabbits in Australia and kudzu throughout the southeastern United States decimating native species and upsetting ecosystems. Until now, biologists studying these events have not seriously considered evolution as part of the strategy used by invading species.

But new evidence stemming from the accidental introduction into North and South America of an Old World fruit fly, which has exhibited one of fastest evolutionary changes ever recorded, may alter that perception.

Writing in this week's issue of the journal Science, a team of researchers from the University of Washington, Clarkson University in New York and the University of Barcelona report that the fly, Drosophila subobscura, which was introduced about two decades ago, has already evolved a wing size pattern that mimics that of established populations in Europe In the process, D. subobscura, a black fly less than one-eighth of an inch long, seems to be replacing native fruit flies in the Pacific Northwest.

"Humans are introducing plants and animals all around the globe and, in many cases, those introductions are wreaking havoc on native populations," said Raymond Huey, a UW evolutionary biologist and lead author of the study. "The dynamics of invasions become much more complicated if the invaders evolve rapidly. It is very likely that introduced invading species are evolving, and scientists typically have not appreciated how fast evolution can occur in an introduced species. This probably means native populations will be changing as well in response to introduced species."

D. subobscura is a temperate-zone fly native to a region stretching from Spain northward into southern Scandinavia and from North Africa eastward to the Middle East. In South America, it was first found near the Chilean port city of Puerto Montt in 1978. The flies quickly colonized much of coastal Chile, although scientists detected no change in wing length a decade later. They were initially discovered in North America in the early 1990s in Port Townsend, Wash.

Both introduced populations are nearly identical genetically, leading geneticists to believe they stem from a common stock that hitchhiked on a ship that probably stopped in Chile and in North America sometime around 1978. Since then, the flies have spread over an area spanning more than 16 degrees of latitude in Chile and across the Andes Mountains into coastal Argentina. In North America, D. subobscura has spread from Santa Barbara, Calif., north to the tip of Vancouver Island in Canada. They also have been trapped as far east as near Salt Lake City.

To check for evolutionary change, Huey and his colleagues trapped flies at 11 North American sites in 1997 and 10 in Spain, France, the Netherlands and Denmark in 1998. Then they raised five or six generations of flies in similar environments, measuring the wing lengths of the last generation. Biologists use wing length because it is an easily measured and highly repeatable index of body size.

D. subobscura has occupied temperate Europe for about 10,000 years, since the last ice age, and exhibits a geographic pattern of bigger individuals in areas of higher latitude. Thus wings of flies in Denmark are 4 percent longer than those from Spain. Huey said this probably has some connection with temperature, but the precise reason has yet to be determined.

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Materials provided by University Of Washington. Note: Content may be edited for style and length.


Cite This Page:

University Of Washington. "Rapid Size Change In Introduced Fruit Fly Indicates It Is Evolving As It Invades North America." ScienceDaily. ScienceDaily, 17 January 2000. <www.sciencedaily.com/releases/2000/01/000117071710.htm>.
University Of Washington. (2000, January 17). Rapid Size Change In Introduced Fruit Fly Indicates It Is Evolving As It Invades North America. ScienceDaily. Retrieved March 28, 2024 from www.sciencedaily.com/releases/2000/01/000117071710.htm
University Of Washington. "Rapid Size Change In Introduced Fruit Fly Indicates It Is Evolving As It Invades North America." ScienceDaily. www.sciencedaily.com/releases/2000/01/000117071710.htm (accessed March 28, 2024).

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