Population experiments with the Anolis lizards of St. Maarten and St. Eustatius.

Experiments were performed with 2 two-species guilds of Anolis: A. gingivinus and A. wattsi pogus on St. Maarten and A. bimaculatus and A. wattsi schwartzi on St. Eustatius (both islands in the Netherlands Antilles). On each island 2 enclosures contained only the larger native species (A. gingivinus or A. bimaculatus), and 2 contained both native species. There was more interspecific partitioning of space and prey (arthropods) on St. Eustatius than on St. Maarten. A comparison of the 1- and 2-species enclosures on St. Maarten revealed 5 competitive effects of A. wattsi pogus on A. gingivinus. In the presence of A. wattsi pogus, A. gingivinus individuals had lower growth rates and increased perch heights. Also, dissected A. gingivinus from the 2-species enclosures contained smaller volumes of developing eggs per female, smaller volumes of insect prey per lizard, and smaller mean prey sizes than A. gingivinus from the single-species enclosures. In contrast, no consistent and significant competitive effects of A. wattsi schwartzi on A. bimaculatus were observed on St. Eustatius. Results support a central assumption of competition theory: the strength of interspecific competition increases as the amount of interspecific resource partitioning decreases.-from Authors