( Fast-warming climate appears to be tri...)Evolution of Old World fruit flies on three continents mirrors climate change

"This is a clear signal on three different continents that climate change is occurring, and that genetic change is going along with it," said Raymond Huey, a University of Washington biology professor who is co-author of a paper describing the findings, published Aug. 31 in Science Express, the online edition of the journal Science.

The research deals with an Old World fruit fly species called Drosophila subobscura, which originally ranged from the Mediterranean Sea to Scandinavia. European biologists who studied the insect's genetic makeup more than 40 years ago noted that sections of chromosomes were inverted, something like taking part of a bar code from a consumer product and flipping it backwards. The biologists found that the frequency of particular inversions was correlated with the latitude where a given insect was found. Inversions that were common in the north were uncommon in the south, and vice versa.

The fruit flies were accidentally introduced to the Pacific Coast of Chile in the late 1970s and to the North American West Coast in the early 1980s, probably on cargo ships. They spread rapidly, and in North America they are now found from near Santa Barbara, Calif., to northern Vancouver Island in British Columbia.

The first samples of chromosome inversions were collected at several sites in Europe three to four decades ago, and the same sites were sampled again recently. South American flies were sampled for chromosome inversions in 1981 and again in 1999. In North America, the first samples were collected in 1985 and the most recent came in 2004. The scientists also looked at shifts in weather patterns during the intervals between sample collections. At nearly all sites, temperatures had increased consistent with global warming.