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When The Environment Shifts, CSU Study Finds Evolution Can Work A Little Faster

Paul Bentzen, via Cameron Ghalambor
Guppies vary in coloration: some, as seen right, are brightly colored, while others are more camouflaged.

Evolution may take place much faster than scientists previously thought. New findings suggest that it’s possible some species could adapt quickly to survive a shifting environment, as in the case of climate change.

Researchers at Colorado State University found that when they took guppies from an area teeming with predators and placed them in an area with no predators, the fish showed changes in genes after just a few generations.

“We found that the chemical cue of a predator is enough to elicit a whole series of changes,” says Cameron Ghalambor, a biology professor at CSU and lead author of the study.

Importantly though, the changes can’t be too abrupt. When Ghalambor ran the experiment the opposite direction -- that is, taking fish from a predator-free environment and placing them in one filled with predators -- the guppies all died.

It can be so fast that if you're not paying attention, you miss it.

Males from the predator-free environments just weren’t prepared biologically for an environment filled with predators. For example, they don’t have the same camouflaged skin as fish that evolved around predators.

“The males are very brightly colored, they use these bright colors to attract females.” says Ghalambor. “They grow more slowly, they live longer, they don’t have as many babies, they’re not as fast, [and] they don’t school as much.”

Yet if the researchers remove the guppies adapted for predators into a more relaxed, predator-free environment, they see the next generations of fish develop brighter colors and slower growth rates. Essentially, the predator-adapted fish develop the physiology and behaviors of the predator-free fish.

"We know that almost all of these behaviors and traits, whether it’s their body shape, their physiology, behavior, have a genetic basis," explains Ghalambor. "These traits are heritable, they’re passed from parent to offspring."

The researchers had seen the guppies' environment trigger physiological changes in previous studies, which is part of why they kept using them as study subjects. Plus, guppies do well in lab settings and reproduce quickly, so the researchers can study several generations in a short period of time.

Ghalambor and his co-authors found significant changes in 135 of the guppies’ genes, all sparked by the fish’s environment. All the changes took place within one year, or a few generations of guppy breeding. This is a very short period on the evolutionary timeline, which can sometimes take hundreds or thousands of years.

The findings, published in Nature, suggest that animals have the ability to adapt more quickly than than researchers previously thought. This could prove vital to their survival in the face of climate change. Yet Ghalambor says that animals might not adapt just the right way, or they might not adapt quickly enough. Just like some of his guppies died in their new environments, those animals might go extinct.

Still, the study shows that evolution is not necessarily a slow process.

"We have more and more evidence that actually, it can be so fast that if you’re not paying attention, you miss it," says Ghalambor.

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