Evolution at Lightning Speed: Fish Adapts in Just 3 Years

Within an incredibly brief period of three years, a small fish has evolved to survive temperatures that are cold enough to have killed its ancestors. The lowly stickleback, a fish no bigger than a human finger, has accomplished something that many scientists had thought impossible. It adapted genetically to a radically different environment and passed that change on to its progeny in just three generations.

At the end of a three-year experiment, scientists at the University of British Columbia, Vancouver, demonstrated that third-generation sticklebacks had increased their cold-water tolerance by a significant 2.5 degrees Celsius (4.5 degrees Fahrenheit.) The research, published in the current issue of the Proceedings of the Royal Society B, involved scientists from Switzerland, Sweden and Canada, and it built upon other work at several additional institutions.

Sticklebacks were saltwater fish until the end of the last ice age, about 15,000 years ago, when many were trapped in freshwater lakes behind receding glaciers. They didn't just adapt to that very different environment. They thrived, changing rapidly to meet changing conditions while abandoning traits, like body armor that was needed in the ocean but not in a lake, and producing radically different species in lake after lake after lake.

That rapid expression of natural selection probably would have stunned even Charles Darwin, and it has caught the attention of a wide range of leading scientists, including David M. Kingsley of the Howard Hughes Medical Institute, who laid the framework for understanding the genetically adaptive stickleback.

But the latest work raises many important questions, because the genes that made it possible for the Canadian sticklebacks to adapt to cold water so quickly must have been present -- although unexpressed -- in the wild fish that were captured and used in the experiment.

So does that mean many species probably have genes necessary to survive in very different conditions, like global climate change? Maybe, but no one knows at this point because relatively little attention has been paid to the question.

And if many species do have the necessary genes, is that a good thing? Maybe, if they are endangered species, but maybe not, if they are pests, or harmful bacteria, but again, nobody knows.

In fact, we wouldn't even know as much as we do had it not been for the pioneering work of biologist Dolph Schluter, who dug more than 30 ponds on the University of British Columbia's Vancouver campus to urge evolution along. He calls the ponds his "evolution accelerator," and for several years now, his students have been breeding sticklebacks and watching the results.

Evolution at Lightning Speed

Rowan Barrett, who received his doctorate from the university just last week, led the latest experiment and is the lead author of the study.

"We replicated what happened at the end of the last ice age," Barrett said in a telephone interview. Barrett and several colleagues collected wild saltwater sticklebacks along the Canadian coast and after a brief period of adjustment in the lab, the wild fish were introduced in three ponds. They started during the summer, when the water was reasonably warm, and progressed through colder and colder seasons over a three year period.

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