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Thursday, 19 October, 2000, 19:18 GMT 20:18 UK
Fishy clue to evolution
Salmon/University of Massachusetts, Amherst
Salmon bury their eggs in rivers or beaches
New animal species can emerge much quicker than previously thought, say scientists.

Salmon in a US lake split into two separate populations in just 13 generations, or about 60-70 years, researchers have revealed.

Until now, it was believed that new species took hundreds or thousands of years to appear.

And, in a separate study, insects were found to alter the way they attracted a mate in just nine generations.

The salmon study took place in Lake Washington, Washington State.

The fish were first placed there in 1937. Since then, they have split into two separate populations which prefer not to breed with each other.

One group adapted to breeding in a river environment. The others laid their eggs on the lake's beaches. As a result, the two populations have developed slightly different physical features.

Rethink necessary

The male river fish evolved shallower bodies that are better for swimming through strong currents. The female river fish were bigger than the lake ones and able to dig deeper nests.

The new evidence suggests that animals can adapt to new environments about 10 times faster than once thought.

Researcher Dr Andrew Hendry of the University of Massachusetts, Amherst, who led the study said: "This should really make us rethink the importance of natural selection and adaptation to the rapid generation of new species and the generation of biological diversity."

In a separate study, researchers at the University of Queensland, Australia, looked at an insect, the fruit fly.

They found that male fruit flies altered the chemicals they use to attract mates after nine generations.

The flies appeared to have evolved mechanisms to identify females of the same species, to improve their chances of breeding success.

Both studies are reported in the journal Science.

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