Rising temperatures cause worldwide genetic changes in Drosophila subobscura
By Charles Q. Choi | August 31, 2006
Global warming is driving worldwide genetic changes in a fly species, scientists reported online August 31 in Science.
These findings reinforce recent studies suggesting that climate change is rapidly leading to genetic impacts "in widespread organisms," Ary Hoffmann at the University of Melbourne in Australia, who did not participate in this study, told The Scientist.
Raymond Huey at the University of Washington in Seattle, along with his colleagues in Spain and Virginia, analyzed Drosophila subobscura, a fruit fly native to Europe. The species was accidentally introduced to Chile in the 1970s and the West Coast of the United States in the 1980s, probably via cargo ships.
The researchers investigated chromosomal inversions, where chromosomal segments flip themselves backward. The first chromosomal inversion samples in D. subobscura were collected in Europe more than 40 years ago. After the fly spread to other continents, geneticists began sampling chromosomal inversion data in South America in 1981 and in North America in 1985.
Past research discovered chromosomal inversions in the fly that were common at low latitudes, where climates are warmer, but uncommon in the lower temperatures of high latitudes, suggesting chromosomal inversions help flies adjust to changes in climate.
To see if global climate warming had any impact on genetics, Huey and his colleagues compared the existing decades of genetic data, gathered over an average of 24 years, with temperature records for the same time periods. In 22 of 26 fly populations examined across three continents, climate warmed over the intervals. Among those 22 populations that experienced warming, the frequency of chromosomal changes characteristic of low latitudes and warmer climates increased in all but one population.
"What is most surprising is that small shifts in average temperature, about ½ degrees C, which seems trivial on a temperature scale, are obviously not trivial to the flies," Huey told The Scientist. "They are immersed in this warmer environment, such that the effect of climate warming is likely compounding over their life span."
Inversions involve large segments of chromosomes and thus many genes, which "makes it hard to determine which particular traits, or groups of co-adapted traits, might be under selection. Trying to figure that out is a goal for the future," Huey said.
Past studies of genetic changes in response to global warming only looked at populations of a species that were distributed over a single continent, at most, Huey said. "Here you have a single species, each interacting with their environments with the same genome over several continents, to help show how global a response this is," William Bradshaw at the University of Oregon in Eugene, not a coauthor, told The Scientist.
These genetic shifts appeared rapid, detectable even for samples from an area taken less than 20 years apart. Future research should investigate the different rates and extents to which species are evolving in response to climate change, Christina Holzapfel at the University of Oregon in Eugene, who did not participate in this study, told The Scientist.
While these and other findings suggest small species with big populations and high reproductive rates can keep up with climate change, many other species might not. Researchers in the Netherlands show birds like the Great Tit are changing, but perhaps not fast enough, "and large organisms might not keep up at all," Holzapfel said. "The organisms most likely to keep up aren't necessarily those we'd like to, like mosquitoes and pathogens," Bradshaw added. The resulting collapse of populations "is the real specter of climate change," Huey said.
Charles Q. Choi
Links within this article
J. Balanya et al. "Global genetic change tracks global climate warming in Drosophila subobscura." Science, published online ahead of print August 31, 2006.
L. Pray. "Adapting to climate change." The Scientist, September 22, 2003.
E. Sole, "Long-term changes in the chromosomal inversion polymorphism of Drosophila subobscura. I. Mediterranean populations from southwestern Europe," Evolution Int J Org Evolution, April 2002.
William Bradshaw and Christina Holzapfel
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