Many southerners will recognize the green anole, aka Carolina anole, aka American chameleon. The scientific name is Anolis carolinensis.
Though sold in pet shops as “chameleons” because of their color-changing ability, they’re not the same as the true chameleons of Africa and Asia.
Green anoles are small, slender lizards that live mostly in trees, but can also be found clinging to window and porch screens. Usually bright green, they can change their color to brown or tan. They have a pink throat fan, or dewlap, which they expand to communicate with other anoles. They are territorial, so what they’re communicating is probably “MY tree! Go away!”
Green anoles live throughout the southeastern coastal plain, where they are a common sight even in urban areas. But their population may be going down. They have a new competitor in the brown anole, an invasive species from the Caribbean.
This is bad news for the green anole, but it does offer humans a chance to see natural selection in action. The brown and green anoles’ ecological niches1 overlap, but are not exactly the same. The brown anole is a better competitor on the ground, but the green anole is a better climber. As the brown anole, which lives mostly on the ground and lower parts of trees, spreads into the mainland US, the green anole plays to its strengths and spends more of its time high in the trees.
This change in behavior would be interesting enough, but there’s also evidence of physical changes. One experiment found that on islands where brown anoles were introduced, the green anoles had evolved larger toe pads, which helps them climb, after only 15 years. On similar islands with no brown anoles, the green anoles were not restricted to the tops of trees, and had smaller toe pads.
A noticeable physical adaptation in 15 years? I believe the scientific term for this is so damn cool.
- An ecological niche is the role an organism plays in its environment, including its habitat, its place in the food web, its behavior, etc. ↩