Green anole lizard adapting to a snowy winter landscape.

Lizard Resilience: How Winter Storms are Reshaping Green Anole Populations

Rhea Morgan in Science & Nature December 2025 • 4 min read.

"Discover how extreme weather events are driving rapid evolution in green anole lizards, revealing nature's surprising adaptability."

Nature often presents us with unexpected events that can dramatically alter the course of life. One such event occurred during the winter of 2013-2014 when the southeastern United States experienced unusually harsh weather conditions. This extreme cold served as a real-world experiment, allowing scientists to observe the direct impacts of natural selection on wildlife populations.

A team of researchers focused on the green anole lizard (Anolis carolinensis) to investigate how these extreme weather events influence survival and adaptation. They examined various aspects, including the lizards' physical traits, gene activity, and overall genetic structure, across different locations.

The study revealed that the cold weather led to significant increases in cold tolerance among lizard populations, especially in the southernmost areas. This remarkable shift suggests that extreme weather events can act as potent drivers of evolution, leading to rapid changes in the genetic and biological characteristics of a species.

Unveiling the Secrets of Cold Tolerance

Green anole lizard adapting to a snowy winter landscape.

The scientists began their investigation by measuring a critical trait: cold tolerance. This is the minimum temperature at which lizards lose their coordination. They assessed lizard populations at five different locations along a north-south line in August 2013, before the severe winter struck.

The winter of 2013-2014 brought significantly colder temperatures than the previous 15 years. This allowed researchers to estimate the intensity of cold stress at each location by calculating how many days each population experienced temperatures below their average cold tolerance threshold.

The southernmost population experienced the most significant increase in days below their cold tolerance limit.
Populations farther north also faced increased cold stress, though to a lesser extent.

To test the hypothesis that the cold weather acted as a selective force, the scientists returned to the southernmost and a central population in April 2014. They measured the cold tolerance of the surviving lizards. The southernmost population showed a significant increase in cold tolerance, whereas the central population showed no change. This increase in cold tolerance persisted even into the summer, suggesting a lasting change rather than a temporary seasonal adjustment.

Adapting to a Changing World

This research underscores how quickly natural selection can act, especially when triggered by extreme environmental events. The green anole lizard's rapid adaptation to colder temperatures provides a compelling example of nature's resilience.

Understanding the mechanisms behind these adaptations is crucial, especially as extreme weather events are predicted to become more frequent due to climate change. By studying how species like the green anole respond, we can gain insights into the broader impacts of climate change on biodiversity and ecosystem stability.

Further research is needed to explore the long-term consequences of these rapid evolutionary shifts. However, this study highlights the remarkable capacity of species to adapt and survive in the face of environmental challenges, offering a glimmer of hope in a rapidly changing world.

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This article is based on research published under:

DOI-LINK: 10.1126/science.aam5512, Alternate LINK

Title: Winter Storms Drive Rapid Phenotypic, Regulatory, And Genomic Shifts In The Green Anole Lizard

Subject: Multidisciplinary

Journal: Science

Publisher: American Association for the Advancement of Science (AAAS)

Authors: Shane C. Campbell-Staton, Zachary A. Cheviron, Nicholas Rochette, Julian Catchen, Jonathan B. Losos, Scott V. Edwards

Published: 2017-08-04

Everything You Need To Know

What triggered the changes observed in the green anole lizard populations?

The winter of 2013-2014 brought unusually harsh weather to the southeastern United States, creating a 'real-world experiment'. The extreme cold acted as a catalyst for natural selection, directly impacting wildlife populations and providing a unique opportunity for scientists to observe evolutionary changes in real-time. This event allowed researchers to study how specific traits and genetic make-up of the green anole lizard changed in response to environmental pressures.

How did scientists measure the impact of the cold weather on the green anole lizards?

Researchers measured cold tolerance, defined as the minimum temperature at which lizards lose coordination, to understand how the extreme cold affected the green anole lizard populations. This involved assessing the cold tolerance of the green anole lizards before the winter storms, and then again after, to determine how their ability to withstand cold temperatures changed. This allowed the scientists to observe the direct effects of natural selection and adaptation to environmental changes. The southernmost population experienced the most significant increase in days below their cold tolerance limit.

What specific adaptations did the green anole lizards exhibit in response to the extreme cold?

The green anole lizards displayed rapid adaptation, particularly in the southernmost populations, where they showed a significant increase in cold tolerance after the winter of 2013-2014. This demonstrated the power of natural selection in driving rapid evolutionary changes. The central population showed no change. The extreme cold acted as a selective force, favoring individuals with a higher cold tolerance, which allowed them to survive and pass on their genes. This change persisted even into the summer, suggesting a lasting adaptation.

What is natural selection, and how did it influence the green anole lizard populations?

Natural selection, in the context of the green anole lizard, is the process where environmental pressures, like the extreme cold of the winter of 2013-2014, favor certain traits within a population. Lizards with a higher cold tolerance were more likely to survive, reproduce, and pass on their genes. Over time, this leads to a shift in the genetic and biological characteristics of the population, making them better suited to their environment. The green anole lizards' rapid adaptation to colder temperatures highlights the speed at which natural selection can operate.

Why is this research on the green anole lizard important, and what are the broader implications?

The implications of this research are significant as they highlight the adaptability of species in the face of environmental change. The study on the green anole lizard demonstrates how quickly natural selection can act, especially when triggered by extreme weather events. This knowledge is crucial for understanding how wildlife populations might respond to climate change and other environmental stressors. It provides a compelling example of nature's resilience and the potential for rapid evolution, emphasizing the need for continued research into these processes.