Lizards may be evolving to survive hurricanes in Caribbean

Reptiles that survived hurricanes had adaptations that allowed them to hold on tighter to trees

Lizards on Caribbean islands appear to be evolving the ability to withstand the forces of massive tropical storms that batter their homes every year.

Scientists studying tropical anole lizards on the remote islands of Turks and Caicos, near the Bahamas, were forced to beat a hasty retreat in late 2017 when Hurricane Irma battered the region.

After the storms had died down, lead researcher Dr Colin Donihue realised it presented them with a unique opportunity to investigate the effects of hurricane-induced natural selection.

So together with a research team, he travelled back to their recently abandoned research site on the devastated archipelago and set about repeating the measurements of various body parts on the lizards that had not been blown away by the violent gales.

“Something like this has never been documented before because it’s so difficult. The timing had to be just right,” explained Professor Jonathan Losos, a Washington University biologist who worked on the study. “The prediction was that if we saw any changes, they would be changes in the features that help lizards hold on – they would be related to clinging ability.”

They found that the few lizards that remained on the islands had larger sticky toe pads on their feet, as well as longer forelimbs and shorter hind limbs.

These results, published in the journal Nature, suggest that the surviving lizards were those with attributes that allowed them to cling on to branches better.

To test how lizards respond to violent winds, the scientists exposed lizards from the surviving population to simulated hurricanes and watched how they responded.

Their tests confirmed that lizards try to hold on tight to branches, but that their hind limbs were vulnerable to being blown off first. This explained why the survivors had shorter hind limbs.

While the scientists are far from certain that they are observing evolution in action, they are keen to conduct further research to work it out.

“Perhaps the hurricane blew in lizards with bigger toe pads and shorter hind legs from another island,” Prof Losos said. ”Or perhaps the act of clinging to the branches in high winds actually caused their forelegs to get longer.”

“We can’t rule these possibilities out because this study was the result of serendipity, rather than specifically being designed to test the effect of hurricanes. Still, hurricane-induced natural selection seems like the best explanation for these findings.”

As hurricanes become more frequent due to climate change, the scientists now intend investigate how their impact on these tiny islands is driving the evolution of their inhabitants.