What Ants Can Teach Us About the Effects of Climate Change

May 15, 2017

Scientists are devising new ways to predict the effects that climate change will have on the earth. Rising sea levels and unpredictable weather patterns are some of the large- scale outcomes, but in this week’s Exploradio, WKSU’s Jeff St.Clair looks at how climate change is playing out on a much smaller scale.

Acorn ants are tiny.   

Sarah Diamond opens a plastic container, one of dozens sitting in a refrigerator-sized incubator, to reveal the honey-gold specks racing back and forth from under a small clump of leaves.

Researcher Sarah Diamond studies the effects of climate change on natural systems. She's raising acorn ants in her lab to study how city ants have evolved to the pressures of urban life.
Credit JEFF ST.CLAIR / WKSU

A whole colony of acorn ants, about 250 individuals, can live inside the empty husk of an acorn shell, "although this is a hickory nut that these ants are living in right now,” says Diamond.

She’s breeding the ants for an experiment in her lab at Case Western Reserve University.

“It’s like the classic 5-year-old kid with a magnifying glass experiment,” she laughs, "but on a higher level."

In the experiment, she places an acorn ant inside a tiny tube, places it into an aluminum block heater, and then she cooks it until it stops moving.

The goal is to measure the ants' heat tolerance, the temperature at which these ants can no longer function.

She also cools them down to measure the ants’ lower temperature range.

The acorn ant Temnothorax curvispinosus is a tiny ant found across the eastern U.S. It typically nests in empty acorn shells. Researchers in Cleveland have found that over the past 100 years, urban acorn ants have evolved a higher heat tolerance than their rural cousins.
Credit ANTWIKI

She’s finding that some ants have a much higher heat tolerance than others. 

The reason?  They’re city ants. 

Turns out not all the ants in the incubator are identical. Some came from Cleveland, others from the woods surrounding the Holden Arboretum 20 miles away.

And which ants are better at taking the heat?

Cleveland, she says, is around 3 degrees warmer, on average, than the surrounding countryside, and the city ants have evolved over the past 100 years or so to have a higher heat tolerance than their rural cousins. 

She's also looking into the genetic and other behavioral changes city ants have undergone in their urban evolution.   

Small Scale Climate Change
Adapting to city life is a good model for climate change, but Diamond and other scientists are also studying what a warming earth will mean to ants and other animals in the wild.

That’s why she and her colleagues designed a massive, five-year experiment to see how increasing heat affects forest ecosystems.

“It was one of the largest manipulations in the world,” says Diamond.

In the experiment, researchers built 15 climate-controlled plots in North Carolina and Massachusetts. Hot air was blown into the enclosure, simulating a warming environment.
Credit SCIENCE ADVANCES

In the experiment, a system of heating ducts blew hot air onto fenced off plots of forest maintaining temperatures up to 5 degrees warmer than the surrounding area.

Fifteen of these plots were maintained for five years in two states, North Carolina and Massachusetts.

Nick Gotelli teaches biology at the University of Vermont and was one of the architects of the study.

He predicted that warmer temperatures would speed up the life cycles of the different ant species.

“But that’s not actually what happened,” says Gotelli.

Regime Change in the Ant World
Instead, the patches of forest looked more like episodes of “Game of Thrones” with sudden and dramatic regime shifts in the ruling ants.

“We identified what we called winner species and another group called loser species based on how they interact with each other and how they interact with the climate.”

Why does it matter?

Ants, as you know, are everywhere. They’re nature’s clean-up crew.  They’re crucial in seed dispersal for plants.

Credit FLICKR CC

They play a huge role in decomposition; ants excavate far more dirt than earthworms, says Gotelli. "So any change in the composition of ants could cascade into big changes in the appearance and structure of our forests.”

Another surprise for Gotelli and Diamond was that ants in the south were much harder hit by climate change than similar communities in the north. 

“So that’s important because climate change is not going to operate the same way across the whole globe,” says Gotelli.

Some northern latitudes like Ohio, he says, could be buffered somewhat from the changes wrought by rising temperatures.

They've Got High Hopes
Sarah Diamond at Case Western says it’s important to study subtle changes of a warming planet along with looking at the long-term trends.

Sarah Diamond studies evolutionary ecology and global change biology at Case Western Reserve University.
Credit JEFF ST.CLAIR / WKSU

“We might have some hidden consequences of climate change that we’re not really seeing with these other ways that measure responses,” says Diamond.

Ants have always been seen as steadfast survivors known for overcoming obstacles, and that’s still true.

They will survive.  

But this study shows even in the ant world, there will be winners and losers on a warming planet