Anolis cristatellus, a medium-large brown anole native to Puerto Rico, its satellite islands and the Virgin Islands group, has been introduced at La Romana on the south coast of the Dominican Republic. The time and circumstances of introduction are unknown, but it is thought to have occurred before 1920 in the port area southeast of the town. The species has become well established and phenomenally abundant, occupying an area of about 12 km2 and 13 km long. However, it is closely confined to the town of La Romana and adjacent altered areas with parks, gardens and evergreen trees, more mesic in aspect than adjacent relatively natural areas that are characterized by exposed limestone surfaces and chaparral-like formation of thorny shrubs and low, gnarled trees. The introduced A. cristatellus is closely associated with at least three species of native anoles. Anolis distichus is abundant both in the area invaded by A. cristatellus and in the relatively undisturbed habitat where cristatellus is absent. The two species often occur together on the same tree, and their height preferences coincide. Their food habits are similar, but with difference in average size of prey. Ants are a major food source for both. The smaller A. distichus may avoid predation by A. cristatellus through its greater agility. Anolis chlorocyanus is similar in size to A. cristatellus, but where the two co-occur, it is almost confined to trees with smooth and slippery trunks that are avoided by cristatellus; A. cybotes, a large, aggressive, predatory species, similar in habitat preference to A. cristatellus was found only outside the cristatellus area or on its edges. It seems that A. cristatellus is limiting to cybotes perhaps by preying on its hatchlings and outproducing it with shorter generation time and more frequent egg production.