How a population of lizards was forever changed by 2017's extreme hurricane season

The extreme winds from last year's destructive hurricane season seems to have come with some unexpected consequences.  

Hurricanes Irma and Maria — some of the most destructive in Caribbean history — may have forced rapid evolutionary change in a native population of small-bodied anole lizards (Anolis scriptus), researchers in the West Indies say.

SEE ALSO: Hurricanes are slowing down. Here's why that's very bad news for everyone.

 

According to a new study about the lizards released in Nature this week, much of the surviving population of lizards after the hurricanes have larger toe pads, longer forelimbs, and shorter hind limbs than the average anole.

Still of lizard clinging to an experimental perch in hurricane-force winds. Wind speed meter is displaying in miles per hour. (Credit: Colin Donihue)

Those long forelimbs and toe pads would have allowed these anoles to cling to surfaces during gale-force winds brought by the hurricanes. 

Effectively, this means that the hurricanes forced natural selection in real-time, the scientists suggest.

“Day in and day out, natural selection favors those lizards who can run around branches, find food, and find mates,” lead author of the study Colin Donihue said in an interview. 

“It’s only in these atypical instances like hurricanes that we would be able to see a shift away from historical selection.”

With the frequency and intensity of hurricanes ramping up, species within affected ecosystems are being forced to adapt to extreme conditions.  

It's even possible that certain adaptations might aid survival chances in one instance, and hurt them in another, Martha Muñoz, an evolutionary biologist not affiliated with the study, said.

"One trait can enable survivorship in a storm, like shorter hind limbs, but on a daily basis longer hind limbs will help these animals escape predation because it helps them run faster," Muñoz said. 

But it would take an entirely different study to determine how this selection affects the future of the species, and findings like this are rare.

In fact, the data from Donihue and colleagues was due to a coincidence. They had just completed a survey of the lizard population immediately before the hurricanes swept through the island. After the hurricanes, they recognized that they had a unique opportunity, and decided to return. 

The hurricanes key to their research, Irma and Maria, have gone down as two of the worst natural disasters to affect the Caribbean — where it's possible that almost 5,000 people have lost their lives. And a year later, some places affected, like Puerto Rico and Dominica, still don't have power. 

See photos of Irma's aftermath: 

16 PHOTOS
Aftermath of Hurricane Irma in Florida
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Aftermath of Hurricane Irma in Florida
A destroyed trailer park is seen after Hurricane Irma strikes Florida, in Plantation Key in the Florida Keys, U.S., September 12, 2017. REUTERS/Carlos Barria
A destroyed trailer park is seen after Hurricane Irma strikes Florida, in Plantation Key in the Florida Keys, U.S., September 12, 2017. REUTERS/Carlos Barria
Local residents walk along a destroyed trailer park after Hurricane Irma strikes Florida, in Plantation Key in the Florida Keys, U.S., September 12, 2017. REUTERS/Carlos Barria
A boat is seen on a highway as local residents return to a destroyed area after Hurricane Irma strikes Florida, in Plantation Key in the Florida Keys, U.S., September 12, 2017. REUTERS/Carlos Barria
MIAMI BEACH, FL - SEPTEMBER 12: Maria Soto and Michael Perez return home for the first time after seeking shelter in a friend's home when Hurricane Irma passed through the area on September 12, 2017 in Miami Beach, Florida. Florida took a direct hit from the Hurricane. (Photo by Joe Raedle/Getty Images)
The damaged house of Stasia Walsh is seen at the Enchanted Shores manufactured home park in Naples, Florida, on September 11, 2017 after Hurricane Irma hit Florida. / AFP PHOTO / NICHOLAS KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)
BONITA SPRINGS, FL - SEPTEMBER 10: Don Cole removes belongings from his home that was flooded by Hurricane Irma on September 12, 2017 in Bonita Springs, Florida. On Sunday Hurricane Irma hit Florida's west coast leaving widespread power outages and flooding. (Photo by Mark Wilson/Getty Images)
FLORIDA KEYS, FL - SEPTEMBER 11: Overturned trailer homes are seen in the aftermath of Hurricane Irma on September 11, 2017 over the Florida Keys, Florida (Photo by Matt McClain -Pool/Getty Images)
FLORIDA KEYS, FL - SEPTEMBER 11: Damage to a roof is seen in the aftermath of Hurricane Irma on September 11, 2017 over the Florida Keys, Florida (Photo by Matt McClain-Pool/Getty Images)
NAPLES, FL - SEPTEMBER 11: A destroyed gas station is seen after Hurricane Irma passes in Naples, Fla. on Monday, Sept 11, 2017. (Photo by Jabin Botsford/The Washington Post via Getty Images)
IMMOKALEE, FL -SEP 11: Adela Silverio tries to put back a window that was blown out from its frame on her trailer during Hurricane Irma. -The town of Immokalee, Florida was hit hard by Hurricane Irma. The community has many farm workers that live in poor living conditions and their homes seemed to be hit the hardest by the storm. (Photo by Michael S. Williamson/The Washington Post via Getty Images)
A car drives past fallen palm fronds in Naples, Florida, on September 11, 2017 after Hurricane Irma hit Florida. Millions of Florida residents were without power and extensive damage was reported in the Florida Keys but most of the Sunshine State appeared to have dodged forecasts of catastrophic damage from Hurricane Irma. / AFP PHOTO / NICHOLAS KAMM (Photo credit should read NICHOLAS KAMM/AFP/Getty Images)
KEY WEST, FL - SEPTEMBER 11: A sunken boat is shown in the aftermath of Hurricane Irma on September 11, 2017 in Key West, Florida. (Photo by Matt McClain-Pool/Getty Images)
JACKSONVILLE, FL - SEPTEMBER 11: Justin Hand navigates storm surge flood waters from Hurricane Irma along the St. Johns River on Sept. 11, 2017 in Jacksonville, Florida. Flooding in downtown Jacksonville along the river topped a record set during Hurricane Dora in 1965. (Photo by Sean Rayford/Getty Images)
JACKSONVILLE, FL - SEPTEMBER 11: The St. Johns River rises from storm surge flood waters from Hurricane Irma on Sept. 11, 2017 in Jacksonville, Florida. Flooding in downtown Jacksonville along the river topped a record set during Hurricane Dora in 1965. (Photo by Sean Rayford/Getty Images)
JACKSONVILLE, FL - SEPTEMBER 11: The St. Johns River rises from storm surge flood waters from Hurricane Irma on Sept. 11, 2017 in Jacksonville, Florida. Flooding in downtown Jacksonville along the river topped a record set during Hurricane Dora in 1965. (Photo by Sean Rayford/Getty Images)
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The literature on the impact of extreme weather events on localized animal populations is a relatively scarce, but burgeoning field due to increased extreme weather. 

A study published in 2017 found that a polar vortex that hit the Southeast in 2014 drove selection in a population of green anole lizard. 

The researchers behind that study were able to survey the population of lizards before and after the weather event, and found that the surviving population of lizards had many of the genetic qualities in northern populations of the same species. For example, the surviving lizards had an abnormally high tolerance for cold weather in that region.

Aside from these two studies, there isn’t much known about how fast-acting extreme weather events change animal populations on a large scale. 

But with extreme weather events becoming more and more common as human-caused climate change continues, it’s likely that the common agents of natural selection will shift toward those which influence survival during these catastrophes. 

“The key to this study is understanding that natural selection is on-going and is constantly in the background,” Donihue said

The next step? Muñoz suggests going back to the island a year later and measuring the new generation of lizards to see if this natural selection has truly translated into evolution. 

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