Darwin's lizards: like Galapagos' finches, anoles of the Greater Antilles have proved to be eminently adaptable

Natural History, Dec-Jan, 1997 by Jonathan B. Losos, Kevin de Queiroz

Given their diversity, one might predict that these island anoles have been in the Caribbean for quite some time, and indeed they have. Few anole fossils exist, but a dozen amber-entombed specimens, all but one from deposits in the Dominican Republic, are from fifteen to twenty million years old. When we compared two of these specimens with living Dominican species, we found that the fossil lizards were virtually identical to the shorter-limbed, color-changing tree lizards on the island today. Our studies could not reveal whether the fossil anoles and extant Dominican lizards are close relatives or distant relatives that have converged to look alike. But they do indicate that the evolutionary convergence observed today in lizards throughout the Greater Antilles is an ancient phenomenon.

Even without fossils, much can be inferred from comparisons of living species. For example, all Jamaican anoles, with the exception of the brown anole (a natural colonist that arrived from Cuba relatively recently, perhaps a few thousand years ago), have a unique combination of skeletal features, suggesting that they descended from a single ancestral species that originally colonized the island. DNA studies support this conclusion, showing that anole evolution proceeded essentially independently on each island. Furthermore, with one possible exception, the anoles that became specialized to use a particular habitat on one island are not closely related to their ecological counterparts on the other islands.

Despite decades of work by many researchers in the Caribbean, new species of anoles are still encountered every year. The mountains of eastern Cuba, a particularly rich source of new discoveries, are being investigated by teams of biologists from the United States and Cuba. At the same time, however, the destruction of natural habitats is threatening the survival of some species. The large Roosevelt's anole, from the islands east of Puerto Rico, is already feared extinct, and several other forest-dwelling species from Central America are known to have inhabited areas that are now completely deforested. One can only guess bow many species have perished along with the forests of Haiti, which now occupy only 2 percent of their original area. While some of the more common anoles thrive in human-altered habitats, others are sensitive. Only by conserving island forests can the natural laboratories of lizard evolution be preserved for the enjoyment and the enlightenment of future generations.

Welcome to the Sunshine State

Florida is one of the most biologically rich areas in North America, but not all of its fauna is native. Today, the most abundant anole in Florida is an emigre from Cuba. Common and widely distributed in the Caribbean, the six-inch-long brown anole can be found perched on almost any tree trunk, brush pile, or fence post in its range. In the 1960s, the brown anole was generally restricted to Florida seaports, but it has since flourished and spread northward. Its ascendancy, however, has come at a cost to the native green anole. (This lizard, sometimes misleadingly called the American chameleon, is often sold in pet stores.) Although little data about the interactions of the native and introduced species have been published, any Florida old-timer will tell you the same thing: before the brown anole arrived, green anoles were a lot more common. In all, seven anole species have been introduced into Florida. They include representatives of all four Greater Antillean radiations the largest of all 400 living anole species, the eighteen-inch-long Cuban knight anole.