From twitching lizards to noisy frogs, adaptation is often survival of the weird

By Matt Swayne
July 28, 2015

To paraphrase Hunter S. Thompson, when the going gets weird, the weird turn adaptive.

Forces like climate change and globalization are making the world smaller, hotter, noisier and weirder than ever and this is putting even more pressure on species to quickly adapt, according to Tracy Langkilde, associate professor of biology.

"I think the rate of environmental change is increasing," says Langkilde. "Even though the world has never been a stagnant place, these animals are facing more dramatic and faster changes than they ever had before."

Those adaptations are happening right now, she says, and, in some cases, right in our own backyards. Langkilde and the members of her lab are studying how invasive species, such as pugnacious fire ants and loudmouth Cuban tree frogs, are forcing native species in the southern U.S. to adapt -- or die trying.

Don't Just Do Something, Stand There

First I was afraid. I was petrified.
-- Gloria Gaynor

Eastern fence lizards, a medium-sized lizard that lives mainly in the southeastern U.S., had a fairly disco-era Gloria Gaynor approach to survival -- they did nothing. Relying on its camouflage and perfect stillness, a lizard would simply wait until the threat passed. That worked for thousands of years, until fire ants, which probably stowed away in cargo containers on ships from South America, began to move into their habitat. Fire ants are not fooled by the statue of lizard act and immediately begin to bite -- and eventually kill -- the lizards, Langkilde says.

But some lizards grabbed their boogie shoes and took an adaptive twist to survive these fire ant attacks. Actually, it's more of an adaptive twitch.

"The longer the lizards have been around fire ants, the more likely they are to do what we would expect them to do -- twitch around, flick the ants off and run away," says Langkilde. "That would be the natural response to fire ants, but because the lizards have never encountered fire ants before, they don't have this natural instinct, so it has taken awhile for that adaptation to happen."

Langkilde and her team of researchers noticed that in areas where the fire ants have moved in recently, only a small portion of the lizards twitched their way out of danger. In areas of Alabama, where fire ants have lived for decades, nearly 80 percent of the lizards showed the twitching behavior.

Besides learning a new step or two, some lizards are actually changing physically. The hind limbs of some lizards are longer in fire ant-prone areas, she said.

"As soon as they hatch out of the eggs they have longer legs," said Langkilde. "That allows them to reach farther to flick the ants off and have more exaggerated body twitches."

The researchers have also seen other adaptations. Baby lizards in fire ant territory often avoid eating the ants, while lizards that are unfamiliar with the bug eat them -- and can die if they eat too many.

Though these adaptations might be successful in the short term, Langkilde wonders whether these changes come at an evolutionary cost.

"We haven't looked into this yet, but while having longer legs is usually good for living on the ground, these lizards like to climb, so what happens if having longer legs throws their center of balance off?" she says.

As the globe warms, fire ants are traveling farther north, which may force lizards living in the north to also find out that life is a twitch, or you die.

Stayin' Alive

Whether you're a brother or whether you're a mother, You're stayin' alive, stayin' alive.
-- Bee Gees

The researchers are finding evidence to suggest that the stress of dealing with a changing environment is being passed on to new generations of lizards.

"We do have some evidence that stressed-out moms have different babies," says Langkilde. "If you have a mom that's stressed out while she's producing eggs, she may have babies that are born bigger and grow faster -- so she's souping her babies up to be able to deal with stressful situations."

What is difficult for the researchers to determine is whether the creation of these souped-up super babies is due to evolution, involving genetic change, or to how stress alters the mothers' behavior and physiology. Stress could cause the mothers to eat differently, or pass on nutrients to the eggs differently, or even bask differently. Higher stress hormones could also affect the development of the embryo.

Global Volume Change

Don't cry out loud. Just keep it inside and learn how to hide your feelings.
-- Melissa Manchester

It is not just the pollution released into the air and water that is wreaking havoc on the environment, the researchers say. Noise may also be causing harm.

The world is becoming an increasingly noisy place, says Langkilde—and not only because of planes, trains, automobiles, and industry. “We’re also looking at some of the noise associated with introduced species," she says.

Langkilde's lab is investigating how Cuban tree frogs, which range from 3. 5 to 5.5 inches long and can change color to suit the temperature and environment, are affecting native species in the U.S. Like bad neighbors who have invested way too much money in stereo equipment, the frogs are blasting out their neighbors with a chorus of loud, raspy calls that would make Studio 54 seem tame, at least sonically.

"For species that rely on sound -- either to hear predators coming or to be able to hear advertising mates -- having a noisy environment could be a problem," says Langkilde. Native frogs might be able to adapt by calling loudly enough for prospective mates to hear them above the booming voice of the loquacious Cuban tree frog—but at the same time they might also reveal themselves to more predators.

Back To Where Weird Started?

We gotta get right back to where we started from…
-- Maxine Gayle

Some environmentalists suggest that the easiest fix for twitching lizards, loud frogs, and other examples of the world's increasing weirdness is to just put the environment back the way it was. Unfortunately, in all deference to Maxine Gayle, getting back to where we started may not be that easy.

The environment, like an egg, is much easier to shatter than it is to put back together. Even if invasive species are eradicated from an area, things won't necessarily go back to normal. There are often unanticipated costs for successful adaption, says Langkilde. Native species that were able to adapt to changes brought by invaders may find some of those adaptations have negative consequences.

However, Langkilde hopes that her lab's work will lead to insights into how to manage wildlife in this age of increasing environmental change.

"If we can get a good understanding of the sorts of species that can adapt -- like these lizards do -- and the sorts of species that can't, then we can start figuring out how to prioritize things," she says. "We have limited time and effort and dollars to put into management."

Langkilde, who hails from Australia, says that the biodiversity in her home continent not only stoked her interest in biology, but served as an early laboratory for her study of how animals struggle to adapt in changing conditions. Australia is a mostly isolated area and native species aren't always equipped to deal with the arrival of new animals, she says.

Her doctoral and post-doctoral work focused on how introduced species can co-exist -- or not – with the native species in an area. She was particularly interested in how animals adapt to changing environmental conditions, and using that as a window on past adaptation and evolution.

“Watching how introduced species and native species interact and change when they come into contact with one another is a way to see evolution as it happens,” says Langkilde. “It’s like having a time machine.”


  • Tracy Langkilde portrait vertical

    Penn State biologist Tracy Langkilde studies how native species adapt (or fail to adapt) when faced with competition, predation, and other challenges from invasive species.

    Read more ›
    IMAGE: Patrick Mansell
  • Lizard

    The Eastern fence lizard, a native of the southeastern United States, is just one of many species facing threats from invasive species. Penn State biologist Tracy Langkilde is finding that even if a native species can adapt and co-exist with the newcomers, those adaptations often come at a cost.

    IMAGE: Provided by Tracy Langkilde
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Last Updated July 30, 2015