GECKOS EVOLVE RAPIDLY IN BRAZIL AFTER NEW DAM CONSTRUCTED

- story published by Science

The construction of a dam in central Brazil has spurred remarkably fast evolution of geckos in the region. In just 15 years, the lizards’ heads have grown larger—an adaptation that allows them to eat a wider assortment of insects made available by the dam’s creation. The find may portend other rapid evolutionary changes across the globe as humans continue to dramatically alter the natural landscape.  

Starting in 1996, the dam flooded a series of valleys in Brazil’s savannalike Cerrado region, creating nearly 300 islands out of what was once high ground. Many of the area’s largest lizard species disappeared from the new islands, likely because there wasn’t enough food to support their energy needs. But a small, dragonfly-sized gecko called Gymnodactylus amarali—a termite eater once common across the flooded area—persisted on at least some of them. This created an opportunity: Larger termites, which had previously been eaten by the larger lizards, were now readily available to the geckos.

But there was a hitch. The geckos had small heads—only 1 centimeter wide—and some of the termites were nearly the same size. Eating them presented a challenge, kind of like a house cat trying to put a squirrel in its mouth.

To figure out whether the geckos were able to adapt, Mariana Eloy de Amorim, an evolutionary ecologist at the University of Brasília, and colleagues collected some animals on five of the islands in 2011 and compared them with geckos collected at five locations along the edge of the dam’s reservoir, habitat that was not isolated by flooding. They measured the size of the geckos and, after euthanizing them, cut open their stomachs to figure out what they had been eating. 

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