Climate Change Generated Mixed Responses in Ice Age Vertebrates

by AMNH on

Research posts

A new study led by Museum researchers and published in the journal Ecology Letters reveals that, contrary to expectations, vertebrate species in the eastern United States responded to climate change differently over the last 500,000 years. The analysis provides a window into how animals might react to any kind of climate change, whether glacial cycles or global warming. 


American toad surrounded by blades of grass.
Tetrapods in Eastern North America, like the American toad, were not all affected equally by climate change.
© E. Myers

“A big glacier should have affected everybody. It doesn’t matter if you’re a snake or a bird, it probably makes it hard to live there,” said Frank Burbrink, an associate curator in the Museum’s Department of Herpetology and lead author of the study.

“So did these communities all change together as if they were one unit? There’s never been a study that has comprehensively analyzed whether vertebrate communities responded to the glacial cycles in a uniform way.”

To analyze the impact of climate change following the Quarternary period, about 2.5 million years ago, researchers from the Museum, the ‘Iolani School in Honolulu, the City University of New York’s College of Staten Island, and Louisiana State University focused on the historical population sizes of tetrapods—snakes, lizards, mammals, birds, turtles, salamanders, and frogs—in the Eastern Nearctic over the last 500,000 years. They did this by looking at the animals’ genomes and modeling the likelihood of their populations growing or shrinking.

“If you look at any individual species, you can see what its population has been doing over time based on how many changes they have in their genome. When populations expand, they have more genetic differences. And when populations are small, they have fewer,” Burbrink said.


Eastern racer snake curled up on dried leaves.
The Ecology Letters study examined the genomes of north American tetrapods including birds, mammals, and reptiles like this Eastern racer.
© F. Brubrink

Researchers did not find the uniform response to climate change within the tetrapod community that they expected. About 75 percent of the animals went through a population expansion, with only about half of those lineages expanding together.

What's more, 25 percent of the populations contracted. The results imply that there are additional layers of complexity involved in this problem.

What do the results mean for the global warming the Earth is currently facing?

“We need to move beyond viewing communities as single units,” said co-author Brian T. Smith, an assistant curator in the Museum’s Department of Ornithology.

“Some species will respond in one way and others will respond in other ways. And there are many external historical, biological, and stochastic factors that will influence how populations respond to global warming.”