Biology
Ecomorphological Diversification in Anolis Lizards Across Microhabitats
Quick fact
Anolis lizards have evolved the same set of about six 'ecomorphs' independently on each major island of the Greater Antilles, meaning that a twig-dwelling anole on Cuba looks and behaves almost exactly like a twig-dwelling anole on Hispaniola, even though they are different species.
Why this is interesting
On different Caribbean islands, you can find almost identical-looking lizards—yet they are not closely related. How can evolution repeat the same shapes over and over?
Read the full explanation
Understanding Ecomorphological Diversification in Anolis Lizards Across Microhabitats
Imagine you are on a tropical island. You see small lizards darting on tree trunks, others leaping between twigs, and some clinging to tall grass. They are all Anolis lizards, but they look different: some have long legs, others have short legs; some have large toe pads, others have tiny ones. These differences are not random. Each lizard is specialized for a particular 'microhabitat'—the specific part of the environment it lives in, like the trunk of a tree versus the thin twigs at the top. The shape of its body matches the way it moves and perches in that microhabitat. For example, a lizard that lives on wide tree trunks has long legs to run fast and big toe pads to grip the bark, while a lizard that lives on thin twigs has short legs to avoid wobbling and small toe pads to cling to narrow surfaces. Because each microhabitat offers different challenges, natural selection favors different body shapes in different parts of the forest. This is called ecomorphological diversification: the divergence of body form in response to different ecological niches.
A deeper explanation
The mechanism behind Anolis diversification is a combination of natural selection and ecological opportunity. When a species colonizes a new island with few competitors, it can spread into many microhabitats. In each microhabitat, individuals with traits that improve their survival and reproduction are favored. For example, on a tree trunk, a lizard with longer legs can run faster to catch prey and escape predators, so long legs become more common in that population. On twigs, longer legs would make balance difficult, so shorter legs are favored. Over many generations, these selective pressures produce distinct body forms—the ecomorphs. What is most striking is that the same set of ecomorphs evolves independently on each island, a process called convergent evolution. The repeatability occurs because the same types of microhabitats exist on each island, applying similar selective pressures. This demonstrates that ecological niches can channel evolution down predictable paths. Understanding this mechanism helps explain how biodiversity arises: when environments offer a variety of niches, species can diversify into many forms, each filling a different role. It also shows how competition for limited resources is reduced when species use different parts of the habitat, allowing many species to coexist.