June 22, 2009
Less than a decade ago Swanne Gordon, a graduate student at UC Riverside, and her team introduced Trinidadian guppies into the Damier River in the Caribbean island of Trinidad. They placed the guppies above a waterfall to allow them to flourish in a largely predator-free environment.
In eight years the guppies had undergone noticeable evolution: they produced larger and fewer offspring.
Trinidadian guppies are small freshwater fish. Photo by: Paul Bentzen.
To test just how well-adapted to their environment the guppies in the test site had become, Gordon and her team introduced a new population of guppies, who lived under heavy predation, into the site.
The team studied the competing populations for four weeks, and found that the locally adapted guppies fared far better, especially the juveniles. Local juvenile survival was over 50 percent higher than the introduced juveniles from the predated population. "This shows that adaptive change can improve survival rates after fewer than ten years in a new environment," Gordon said. "It shows, too, that evolution might sometimes influence population dynamics in the face of environmental change."
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