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Research Reveals Rapid Evolution

UI professor uses DNA–sequencing tools to understand how Florida anoles adapted quickly to invading species

Off the coast of Florida, dredging material has created a string of tiny islands.

On most of the islands, native green anole lizards have made their home. On some of these, invasive brown anoles have moved in as well. Together, the intermingled populations create a natural experiment.

Researchers including Paul Hohenlohe of the University of Idaho have discovered the green anoles sharing their islands with invaders evolve to be better suited to life higher in the islands’ trees – and fast.

“Sometimes we think of evolution as this long–term thing that happens on long time scales, but really it’s an observable thing that happens on human time scales,” says Hohenlohe, an assistant professor of biological sciences at the University of Idaho.

Hohenlohe and colleagues from the University of Texas at Austin, Harvard University, the University of Massachusetts and Tampa University published a study of the anole populations in a recent edition of the top journal Science.

Anole toes!
Anole toes!

Their research shows that over the course of 15 years and 20 generations, the green anoles on multiple invaded islands first changed their behavior to live higher in the trees, then developed adaptations suited to life on small branches: bigger toe pads and more of the small flaps on the bottoms of their toes that allow them to stick to surfaces.

“It’s another in a string of demonstrations of how rapidly evolution by natural selection can take place, and how we can actually observe it,” Hohenlohe says.

Hohenlohe became involved in the project after Harvard’s Jonathan Losos, who has studied the anoles for decades, spoke at UI through the Department of Biological Sciences weekly seminar series.

The researchers needed to find out whether the green anoles living on different islands were closely related. If they were, the changes could have been the results of shared ancestry, rather than natural selection.

Hohenlohe was the perfect person to help solve the mystery.

As a postdoctoral researcher at the University of Oregon, Hohenlohe helped develop analysis tools for a DNA-sequencing technique known as RAD sequencing.

RAD sequencing allows scientists to sample snippets of an organism’s genome, providing them with enough information to draw conclusions about its genetics without sequencing the entire genome. For the anoles, that meant gathering genetic information at 120,000 locations, rather than 1.8 billion.

“I was part of the first population genomics paper using that technique,” Hohenlohe says. “Since then, this technique has taken off. It’s incredible. It’s been applied to all kinds of plants and animals.”

Using high-tech tools in his lab and in UI’s Institute for Bioinformatics and Evolutionary Studies core research facilities, Hohenlohe analyzed samples from 384 lizards from nine different islands.

The results showed that independent evolution on each island was, in fact, the main contributor to the anoles’ changes.

The researchers then confirmed the changes were genetic by raising island-born lizards in the lab and confirming that the toe-page changes persisted.

“There are all these different components that come together to be able to say definitively that these lizards did in fact evolve in response to the invaders,” Hohenlohe says.

Hohenlohe and his collaborators plan to continue studying the anole populations to see what else they can learn, including using the RAD technique to compare the lizards’ physical traits to their genetic information to find out which genes specifically have changed.

This research will help give scientists better tools for studying evolution in the wild.

“It illustrates the potential of the field of ecological genomics, which is applying genomic tools in natural populations of organisms,” Hohenlohe says.

“We can make the causal connections all the way from specific genes to ecological changes and evolution in nature.”

Read about the Research

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