The Impact of Evolution on the Environment: A Two-Way Relationship

Researchers from the University of Rhode Island have conducted a study revealing how evolutionary changes within species can influence ecological modifications. By observing leg length variations in anole lizards in the Bahamas and their consequential effects on vegetation growth and spider populations, the study suggests that evolutionary traits can impact predator-prey relationships and other ecological interactions, establishing a feedback loop where evolution drives environmental change.

While it is widely accepted that environmental factors shape species evolution, recent research highlights a reciprocal relationship where evolutionary adaptations of species also impact their environment.

A well-known example illustrating this reciprocal relationship is the narrative of the peppered moths. During the Industrial Revolution in England, coal smoke pollution darkened the tree bark near urban areas, making white-bodied peppered moths more visible to predators. Consequently, their population rapidly declined while black-bodied moths, with their ability to blend into the newly darkened environment, flourished and became dominant.

This phenomenon is often cited as a classic demonstration of how environmental changes can drive species evolution. However, researchers have begun exploring the inverse scenario—whether the evolution of a species can influence and initiate changes in its ecosystem.

A recent study by University of Rhode Island researchers provides strong evidence for this phenomenon. Published in the Proceedings of the National Academy of Sciences, the study reveals that evolutionary changes in the leg length of lizards can significantly impact vegetation growth and spider populations on small Bahamian islands. This study represents one of the first instances where such profound evolution-to-environment effects have been observed in a natural setting.

Professor Jason Kolbe, one of the senior authors of the study, explains, “In addition to the environment shaping the traits of organisms through evolution, those trait changes should feed back and drive changes in predator-prey relationships and other ecological interactions between species. We need to understand these dynamics to predict population persistence and anticipate resulting ecological changes.”

For the past two decades, Kolbe and his colleagues have been observing the evolutionary dynamics of anole lizard populations on a chain of small islands in the Bahamas. With around 40 islands of varying sizes, they can closely monitor the resident lizard populations. The islands are sufficiently separated to prevent easy migration between them, allowing distinct populations to remain isolated.

Previous research had shown that brown anoles adapt rapidly to the characteristics of their surroundings. In habitats with smaller brush and tree limbs, natural selection favors lizards with shorter legs, enabling them to move quickly to evade predators or pursue prey. Conversely, lankier lizards thrive in areas with thicker vegetation. Scientists have demonstrated that limb length can evolve rapidly in brown anoles in just a few generations.

In this new study, Kolbe and his team aimed to investigate how this evolved limb-length trait could affect the ecosystems of the tiny Bahamian islands. They created separate populations of short- and long-legged lizards on different islands with no existing lizard populations. The researchers used specialized gear to capture and measure hundreds of brown anoles, selecting those with exceptionally long or short limbs while releasing the rest.

Since the experimental islands were predominantly covered by vegetation with smaller diameters, the researchers anticipated that short-legged lizards would be better adapted to this environment—more agile and adept at catching prey in trees and brush. The key question was whether the ecological effects of these highly effective hunters would be discernible.

After eight months, the researchers revisited the islands to examine ecological differences between those inhabited by short- and long-legged lizard populations. They found substantial variations. On islands with shorter-legged lizards, web spider populations—a significant prey for brown anoles—were reduced by 41% compared to islands with lankier lizards. There were also notable differences in plant growth. As short-legged lizards were better at preying on insect herbivores, plants thrived in their presence. The researchers discovered that buttonwood trees on islands with short-legged lizards exhibited twice as much shoot growth as those on islands with long-legged lizards.

These findings, according to Kolbe, help complete the circle of interaction between ecology and evolution. He states, “We knew from previous research that ecological factors shape limb length, and now we show the reciprocal relationship of that evolutionary change on the environment.”

Understanding the intricate interactions between evolution and ecology is crucial for predicting the outcomes of changing environments, particularly as human activities accelerate both evolutionary and ecological changes worldwide.

Reference: “Experimentally simulating the evolution-to-ecology connection: Divergent predator morphologies alter natural food webs” by Jason J. Kolbe, Sean T. Giery, Oriol Lapiedra, Kelsey P. Lyberger, Jessica N. Pita-Aquino, Haley A. Moniz, Manuel Leal, David A. Spiller, Jonathan B. Losos, Thomas W. Schoener, and Jonah Piovia-Scott, 5 June 2023, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2221691120

The study was funded by the National Science Foundation.

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• University of Rhode Island: Link to the University of Rhode Island website
• Proceedings of the National Academy of Sciences: Link to the study published in PNAS
• National Science Foundation: Link to the National Science Foundation website