Populations of fruit flies on three separate continents have independently evolved identical gene changes within just two decades, apparently to cope with global warming.

“What we’re showing is that global warming is leaving its imprint on genes,” says Raymond Huey at the University of Washington in Seattle, US, who made the discovery with colleagues. “For this to happen in such a short time-frame in so many parts of the world is rather disturbing,” he says.

The researchers analysed DNA from Drosophila subobscura, a species of fruit fly originating in Europe, but which spread to the west coasts of South and North America in the late 1970s. They took samples in 26 locations in Europe, South America and North America where the fly species had been analysed before for chromosomal changes.

These changes, called inversions – constituting a flip of the order of DNA sections – tally with latitude and, by implication, with ambient temperatures.

Comparisons of contemporary and historical profiles of inversions proved that inversions once found only at warmer latitudes had spread as average temperatures had increased further away from the equator, say the researchers.

“At the rates found, the 'warm-adapted inversions' are migrating north at 100 kilometres per 25 years, or 400 kilometres per century,” says Huey. “That’s a lot of gene change.”

Huey points out that the flies typically produce four to six generations per year, “so there is huge scope" for such genetic change. It means that flies can adapt to global warming, but species such as sequoia trees – which have hundreds of years between generations – would not have time to adapt, he says.

It was not possible to establish definitively whether flies had invaded from warmer latitudes, or whether the “warm” adaptation became dominant through selection. “The selection explanation is almost certainly correct because there is excellent evidence that selection acts on inversion [variants] in Drosophila,” says Ary Hoffmann of the University of Melbourne, who has studied “gene migration” in flies in Australia.

Camille Parmesan at the University of Texas in Austin, US, who has carried out similar research, says these new findings are a warning that species may only have limited capacity within their own genomes to adapt to climate change.

Source: New Scientist