actually be predictable based on habitat encountered, and experimental introductions onto formerly lizard-free islands have proven Anolis evolution can be predicted. After appearing on each of the four Greater Antillean Islands about 50 million years ago, Anolis lizards spread on each island to occupy niches in the island's trees. Some living in the tree canopy area, others low on the tree trunk near the ground; others in the mid-trunk area, others on twigs. Each new species developed its own distinct body type, called an ecomorph, adapted to the tree niche where it lived. Together, the different species occupied their various niches in the trees as a "community". A study of lizard fossils trapped in amber shows that the lizard communities have existed for about 20 million years or more. Four modern ecomorph body types, trunk-crown, trunk-ground, trunk, and twig, are represented in the amber fossils study. Close comparison of the lizard fossils with their descendants alive today in the Caribbean shows the lizards have changed little in the millions of years. Behavior As ectotherms, Anolis lizards must regulate their body temperature partly through behavioral changes and bask in the sunlight to gain enough heat to become fully active, but lizards cannot behaviorally warm themselves at night when temperatures drop. Because of this, cold tolerance evolves faster than heat tolerance in these lizards. On the island of Hispanola, both high-altitude and low-altitude lizard populations exist, and the thermal conditions at high and low elevations differ significantly. High-altitude lizards have shifted their ecological niche to boulder environments, where warming themselves is easier, and they show changes in the shape of limbs and skull that make them better adapted to these environments. Species The Anolis lizards that are less susceptible to predation are those with a dewlap in which both the scales and the exposed skin areas between them match the usual pale gray or whitish of the rest of the ventral surface. References Further reading External links Anole Annals, a blog written and edited by scientists who study Anolis lizards Anolis, The Reptile Database Adapting Anolis, short film on adaptations of Cuba's Anolis lizards A Lizard genera Taxa named by François Marie Daudin Fauna of the Dominican Republic