Unveiling the Secrets of Lizard Color Divergence

By: Priscilla Younes, Neyana Fortes, and Jordan Marot (Stonehill College, BIO323: Evolution, Spring 2023)

Overview

In the contrasting environments of the alpine meadows and sand dunes of the Qinghai-Tibet Plateau, two lizard populations have a secret weapon: the ability to use their body color for camouflage and thermoregulation, a local adaptation that helps them survive. Not only have these lizards adapted their colors to hide from predators, but they’ve also regulated their internal temperature using melanin-producing genes. In “Genetically Encoded Lizard Color Divergence for Camouflage and Thermoregulation,” Sun and his team show how the power of local adaptation allows separate populations of toadhead agamas (Phrynocephalus putjatai) to thrive in two distinct habitats. Their study highlights the importance of local adaptation, where species develop traits suited to their specific environments, and how it can lead to the divergence of species to create a new one. With combined data from field observations, genetic analyses, and other experiments, we aim to explain why the lizards developed different colors and how this enhances their survival. Tune into the Evolution Unraveled podcast for a deeper dive into this concept!

The Research and Study System

A 2024 study in the Molecular Biology and Evolution scientific journal examines how lizard coloration adapts differently based on the environment. Sun and his team focused on toadhead agamas because of their distinct light and dark in color variations depending on which environment they inhabit. The dark lizards live in high-altitude, cold meadows, while the light lizards live in warm, sandy areas by a lake.

The study tested if changes in the environment altered lizard dorsal coloration, or the color on the backs of lizards, by switching their habitats. Because no color transformation happened, we know that the color change is not directly caused by their environment, but by their genes. Modeling also showed that their colors helped them camouflage in their natural to avoid being eaten. Additionally, they found that both light and dark lizard skin reflected the natural colors found in their habitats. This means that the lizards’ colors really do help them camouflage themselves!

The scientists also noticed that light and dark colors helped maintain the optimal body temperatures of lizards in both cold meadows and sand dunes. The study linked a difference in a gene called Tyrp1 between light and dark lizards, important because it influences melanin production, a pigment affecting skin color. Using zebrafish, the researchers tested if this difference in Tyrp1 actually affects how much melanin is produced. They found that the dark lizard’s Tyrp1 gene make more melanin, explaining their darker color and thermoregulation advantage.

Implications and Future Studies

This research identifies a new mutation in the Tyrp1 gene that influences melanin production by giving the lizards in colder areas a darker color than those in the sand dunes. In return, their heightened melanin production and darker color help them absorb more heat and avoid predators through camouflage. The same, but opposite, advantages are observed for lizards in the sand dunes with a less active Tyrp1 gene. We come to find out that the light lizards diverged from the darker morphs, who have a fixed mutation in the Tyrp1 gene and a more active Tyrp1 enzyme.

The ability to camouflage from predators and regulate body temperature through coloration is a product of strong selective pressures, or the factors that cause a particular appearance to have better chances at survival and reproduction than another. Because one population lives in a cold meadow and the other lives in a warm sandy area, their contrasting environments act as strong selective pressures in their local adaptations. As a result, these lizards underwent adaptive genetic divergence, the process in which populations of the same species accumulate independent genetic changes, leading to their separation. Their split happened when  the toadhead agamas population divided into different geographic habitats, allowing them to manifest their according skin color over time.

However, we know that more work is necessary to understand the full picture. How does the mixing of genes interact with mutations in this widespread population? What effect does local adaptation have on these lizards’ evolutionary history? The importance of learning more about evolution isn’t a question of time—it’s a necessity for a brighter future. The more we know, the better we can come to appreciate the biodiversity of life and understand our place in the natural world in the face of adversity.

Article: Sun, B.-J., Li, W.-M., Lv, P., Wen, G.-N., Wu, D.-Y., Tao, S.-A., Liao, M.-L., Yu, C.-Q., Jiang, Z.-W., Wang, Y., Xie, H.-X., Wang, X.-F., Chen, Z.-Q., Liu, F., & Du, W.-G. (2024). Genetically Encoded Lizard Color Divergence for Camouflage and Thermoregulation. Molecular Biology and Evolution, 41(2), msae009. https://doi.org/10.1093/molbev/msae009