Volcanoes 101 . Site map . Two female European D. subobscura show natural size differences. The specimen on the left came from Valencia, Spain, and the one on the right was taken from Aarhus, Denmark. George Gilchrist, Clarkson University W hen a foreign plant or animal invades new territory, either because of the vagaries of nature or piggybacked on some human contraption, things change.
Native species can die out in the face of competition, and food sources can be exhausted.
That much scientists knew. But in one invasion, involving a tiny fruit fly, the otherwise eons-long process of evolution sped up dramatically, determining on the fly, as it were, what traits were most useful in the new territory and making changes over a few generations to enhance those characteristics. The invader is Drosophila subobscura , a wee fruit fly native to Europe and surrounding regions. The flies found their way to Chile in the late 1970s and then to Washington State in the early 1990s, mostly likely as stowaways on ships. They have since spread like flies, into Canada, California, Utah and Argentina.