Video Showing Lizards Holding on for Life Shows Natural Selection in Real Time
All the lizards were safely caught in a net.
Over the past decade, climate change has fueled more frequent and more unyielding tropical cyclones. In an effort to prepare for a world fraught with these storms, scientists have set their sights on preparing human populations for the worst. But humans aren’t the only ones massively affected by hurricanes, points out a new study; animals are too, and the disturbances fashioned by these storms may be powerful enough to change some species forever.
Specifically, hurricanes may possibly alter the evolutionary path of a small brown lizard called the Turks and Caicos anole. In a study published last week in the journal Nature, scientists write that they have good reason to think that hurricanes could drive natural selection — a theory that’s been floated before but has never been actually documented.
That’s because they were able to stumble into the silver lining of major misfortune: Four days before Hurricane Irma ripped through the Turks and Caicos Islands in 2017, this team of scientists was in the area studying the morphology of these lizards, technically known as Anolis scriptus. Irma blasted through the islands with 164 mile-per-hour winds, and two weeks later, Hurricane Maria followed the same destructive path, its own winds clocking in at 124 miles per hour. The scientists knew that their little lizards were likely battered — and three weeks after the first storm hit, they returned to see if any of them had survived.
The anole lizard.
There, in the wreckage of the storm, remained some of the anoles. But upon examining of the populations of the surviving lizards, the scientists realized that these lizards differed in body size, relative limb length, and toepad size from those present before the hurricanes hit. This was a big deal because it hinted that the hurricanes had become a force of natural selection, and only the lizards with specific body attributes were equipped to hang on for dear life as their crew was blasted with wind.
“Our serendipitous study, which to our knowledge is the first to use an immediately before and after comparison to investigate selection caused by hurricanes, demonstrates that hurricanes can induce phenotypic change in a population and strongly implicates natural selection as the cause,” the researchers write.
The lizards that survived had longer arms and larger toepads.
But, because they’re scientists, the team decided to double-check if the morphological traits of the surviving lizards — longer arms, shorter legs, and large toepads — really helped them out when the time came to cling on to tree branches. To test this, they set up a makeshift laboratory close to where the lizards lived, set them up on a fake tree, and blasted them with a leaf blower. Overall, they videotaped and evaluated 40 lizards in the simulated hurricane until each of them was eventually and safely blown into a net.
As shown in the videos above and below, certain traits are advantageous when you’re stuck in the middle of a fake hurricane. The little lizard above has a pretty good go at it: Long arms help it cling to the pole, and short legs reduce its drag. The bigger lizard in the video below has legs that catch out like a sail when it’s hit by the wind — not something you want when a storm hits. These experiments allowed the scientist to feel confident about what they saw in the field. Certain traits help you hold on, whether you’re in a storm or in a lab.
“Our study is the first to indicate that hurricanes may indeed be agents of natural selection,” study co-author and Harvard researcher Colin Donihue, Ph.D. writes in The Conversation. “We’re still waiting to see whether future generations of these island lizards — descendants of hurricane survivors — will carry forward the advantageous physical features that were helpful when the 2017 storms hit.”
