Hurricanes Are Reshaping Evolution Across the Caribbean
Two years ago, Colin Donihue, a biologist, released a sober scientific paper along with a series of endlessly GIF-able videos. They showed Caribbean anole lizards flailing in the wind from a leaf blower, holding on to a stick for dear life, not unlike the kitten in the classic “Hang In There, Baby” poster.
No lizards were harmed in Dr. Donihue’s experiment. Video by Colin DonihueCredit
No anoles were harmed. But by proving how a lizard would try to grit its way through hurricane-force winds with sheer grip strength, those whimsical experiments led Dr. Donihue, now at Washington University in St. Louis, and a team of other researchers to a profound suggestion: Extreme weather events may bend the evolutionary course of hundreds of species. A paper published Monday in Proceedings of the National Academy of Sciences offers deeper evidence of their earlier finding.
Across Central and South America and the Caribbean islands, scientists found that lizards with larger toe pads seem to be more common in areas that have been hit by storm after storm in the last 70 years. That suggests that severe but fleeting cataclysms don’t just leave lasting scars on people and places. They also reshape entire species.
“We racked our brains for alternate explanations for this pattern,” said Dr. Donihue. Could it be temperature? Precipitation? Taller or shorter trees in different locations? “Nothing we tried explains that variation as strongly as hurricane history.”
Not long after Dr. Donihue had been lassoing Anolis scriptus lizards with a loop of string at the end of a fishing rod on a pair of small islands in Turks and Caicos for what was supposed to be just a local conservation project, the same islands were blasted by a one-two punch of extreme weather.
First came Hurricane Irma, a screaming maelstrom of 160-mile-per-hour winds. Two weeks later came Hurricane Maria. When Dr. Donihue returned, trees were down and lizards were scarce. On average, he found the surviving anoles seemed to have much bigger, grippier toe pads than the population had averaged before, as if those with less sticky feet had been carried away by the storms.
That initial finding came out with the leaf blower videos. But the team kept digging. Eighteen months after the storm, Dr. Donihue went back to Turks and Caicos a third time to find a new generation of lizards scampering across new plant growth. Those carefree children of the survivors had kept their parents’ generation’s bigger toe pads.
Dr. Donihue and his colleagues then zoomed out, using high-resolution photos from natural history collections to perform the digital equivalent of a sneaker-fitting for 188 different anole species.
Then they compared those measurements to seven decades of historical hurricane data. The same pattern holds: On average, lizards on Caribbean islands slammed by two, three or even four recent direct hits have bigger toe pads than those dwelling on the mainland and other locations that have dodged storms.
Before this, the strongest evidence for how evolution can be shaped by the gauntlet of extreme climate events came from watching Darwin’s finches bounce back after droughts. But that work focused on a single island in the Galápagos.
“Studies like this are still rare,” wrote Peter and Rosemary Grant, the pioneering husband-and-wife research team from Princeton behind that Galápagos research in an email, praising it as “well done.”
Craig Benkman, an ecologist at the University of Wyoming who was involved in peer review of the paper for the journal, said he was confident in the conclusions. And given that climate change is fueling ever stronger storms, he said, more evidence might not be too hard to find. “We need more such studies,” he said. “And unfortunately, we are likely to be overwhelmed with opportunities in the coming decades.”
Now that his team has unveiled the fuller pattern in anoles, Dr. Donihue said he’s hoping other biologists will chase down leads in organisms they study.
“It could also be in plants, trees, snails, who knows?” he said. “I think we’ll see more and more that there are other species whose evolutionary histories, and evolutionary futures, are impacted by survival of hurricanes.”