Aggressive “hulk” lizards are wiping out millions of years of evolution

Science News from research organizations Aggressive “hulk” lizards are wiping out millions of years of evolution Date: April 25, 2026 Source: Lund University Summary: For ages, wall lizards coexisted in three distinct color types, each with its own strategy for survival. Now, a powerful green variant is taking over. These dominant “Hulk” lizards are outcompeting the others, causing yellow and orange morphs to vanish. It’s a dramatic reminder that evolution can flip the script much faster than expected. Share: Facebook Twitter Pinterest LinkedIN Email FULL STORY

For millions of years, a vibrant mix of colors persisted within a single lizard species. Now, much of that diversity has vanished in a remarkably short time. Researchers point to an unexpected cause: a bold green, highly aggressive, and dominant wall lizard that has rapidly eliminated several color forms within its own species.

In many animal species, distinct color types, known as color morphs, are more than just visual differences. These variations often reflect different approaches to survival, such as how individuals compete for territory or attract mates. Each color can represent a unique strategy that helps maintain balance within a population.

A Longstanding Balance in Wall Lizards

The common wall lizard (Podarcis muralis), found widely across the Mediterranean, has long been a classic example of this balance. Individuals typically display one of three throat colors: white, yellow, or orange. For millions of years, these color morphs coexisted within the same populations, maintaining a stable evolutionary system.

That stability is now breaking down. A new study published in Science, led by researchers at Lund University, reveals that this once reliable balance has been disrupted.

"We are seeing how the coexistence of several different color morphs, something that has been stable for millions of years, is being lost over a very short evolutionary time scale," says Tobias Uller, professor of evolutionary biology at Lund University.

Data From Over 10,000 Lizards

To understand what is happening, researchers examined color patterns across about 240 populations, analyzing more than 10,000 individual lizards. The findings were clear. A group informally known as "Hulk" lizards has altered the dynamics within the species.

These larger, more aggressive lizards, recognized by their striking appearance, have spread rapidly. As they expand into new areas, the yellow and orange throat variants are disappearing. In many places, only the white morph remains.

"The aggressive behavior disrupts the finely tuned social systems that previously enabled several color strategies to coexist," says Tobias Uller.

Evolution Can Shift Rapidly

This research highlights how even long standing evolutionary systems can be fragile. While evolution is often thought of as a slow, gradual process, this case shows it can also change quickly when conditions shift.

A single dominant trait can reshape competition and alter the balance within a species in a short time.

"By showing how color variants that have coexisted for millions of years are wiped out, we now better understand how the emergence of new traits changes competition in nature," concludes Tobias Uller.

• RELATED TOPICS
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Story Source:

Materials provided by Lund University. Note: Content may be edited for style and length.

Journal Reference:

1. Tobias Uller, Nathalie Feiner, Roberto Sacchi, Marco Zuffi, Stefano Scali, Panayiotis Pafilis, Konstantinos Plavos, Javier Abalos, Pedro Andrade, Prem Aguilar, Daniele Salvi, Geoffrey M. While. Adaptive spread of a sexually selected syndrome eliminates an ancient color polymorphism in wall lizards. Science, 2026; 391 (6780): 64 DOI: 10.1126/science.adx3708

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Lund University. "Aggressive “hulk” lizards are wiping out millions of years of evolution." ScienceDaily. ScienceDaily, 25 April 2026. <www.sciencedaily.com/releases/2026/04/260424233212.htm>. Lund University. (2026, April 25). Aggressive “hulk” lizards are wiping out millions of years of evolution. ScienceDaily. Retrieved April 25, 2026 from www.sciencedaily.com/releases/2026/04/260424233212.htm Lund University. "Aggressive “hulk” lizards are wiping out millions of years of evolution." ScienceDaily. www.sciencedaily.com/releases/2026/04/260424233212.htm (accessed April 25, 2026).

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