posted 04. August 2006 17:05                    

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Sticklebacks evolved from a relatively uniform marine population into today's broad spectrum of shapes and sizes when the last Ice Age ended roughly 10,000 years ago. Because ocean fish quickly evolved into such distinct populations when they colonized new freshwater lakes and streams, they are an ideal model for understanding how animals adapt to their unique environments.

The recent work carries a few surprises. Kingsley said that the gene in question, called Eda, is an old friend to laboratory researchers who have found that mutations in the same gene in mice cause altered hair patterns. However, in mice similar alterations can also be created by defects in any one of three different genes. "Based on the mouse work you'd predict we would find mutations in any of the three genes in sticklebacks," said Kingsley, who is also a Howard Hughes Medical Institute investigator. "That's not what we see."

Instead, the group found the exact same genetic change in each of the 15 freshwater sticklebacks they studied, including one local species the group collected from a stream near Fresno. Perhaps mutations in the two other genes cause problems for the fish in addition to reducing the number of armor plates, Kingsley said.

Most of these fish evolved independently ...

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