Island lizards get evolutionary upgrade in whirlwind fashion

NATURAL selection usually takes generations to alter a species.

But in a whirlwind example of evolution, lizards living in the British Overseas Territory of Turks and Caicos have been fundamentally altered by a pair of devastating hurricanes last year.

Many of the Anolis scriptus lizards were blown away to their deaths in the violent winds, but after the gales died down, scientists found that the remaining creatures all had abnormally long front limbs and large toepads.

Researchers believe the survivors prevailed because they had – literally – been able to cling on for dear life.

And it means their offspring will also now carry the same elongated adaptation, making it more likely they will survive similar storms in the future.

“Something like this has never been documented before because it’s so difficult, the timing has to be just right,” said Jonathan Losos, a biology professor from Washington University.

“Perhaps the hurricane blew in lizards with bigger toepads and shorter hindlegs from another island. 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 but hurricane-induced natural selection seems like the best explanation for these findings.” The 2017 storm season was one of the worst ever to hit islands in the Atlantic Ocean, with Turks and Caicos battered by hurricanes Irma and Maria in September with wind speeds of up to 170mph.

A team of researchers had been working on the island, monitoring a programme to eradicate rats. They were quickly evacuated, but Colin Donihue, a postdoctoral fellow at Harvard University, realised the storms may have proved a “selective event” with the power to alter the lizards and future generations, based on which had survived.

“Heading back to Pine Cay, we weren’t sure what we’d find, but when we got to the field and saw a few lizards running around, we were eager to get catching and start measuring,” he said. “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. For example, the sticky pads on their fingers and toes, maybe they would be larger.”

The team spent two days collecting and measuring around 100 lizards on the islands and found the survivors had proportionately longer forelegs and smaller bodies. None had long hindlegs, which would have acted like a sail to lift them from the ground.

To test how lizards cling on, they subjected the survivors to hurricaneforce winds in a lab experiment. They found that as the wind speed increased, the lizards first lost hold with their hindlimbs, suggesting larger back legs would have proved deadly in a storm.

The research was published in the journal Nature.