The Anolis Lizards of Bimini: Resource Partitioning in a Complex Fauna

Abstract

The tiny island of South Bimini contains 4 species of lizards of he genus Anolis, a number surpassed only on the 4 largest islands of the Greater Antilles and on 2 very large and nearby satellite islands. These species are syntopic with respect to a two—dimensional area of the ground but divide the habitat according to perch height and perch diameter: sagrei is partly terrestrial but occurs more often on small and large low perches; distichus prefers the trunks and large branches of medium to large trees; angusticipes inhabits small twigs, especially at great heights; and carolinensis is found mostly on leaves or on the adjacent twigs and brances. The size classes of the species are staggered in such a way that the interspecific classes which overlap most in habitat overlap least in prey size. Similarities in prey size and prey taxa for classes of the same species are somewhat greater than those expected on the basis of habitat and morphology alone. The distribution of the species among the vegetation communities of Bimini can be explained on the basis of perch height and diameter preference. Within the same species, the larger lizards usually eat larger food, fewer items, and in sagrei more fruit; and they have a greater average range of food size per digestive tract. One species (distichus) is extremely myrmecophagous: about 75—90% of its food items are ants. In 3 of the 4 species, subadult males take more food and average smaller prey then females of the same head length. That species (distichus) which takes the smallest food items and whose classes overlap the most in habitat preference with those of other species is least dimorphic is size between the sexes. It is suggested that such small, nondimorphic species are best suited for insinuation into complex faunas, whereas larger, dimorphic forms are best for the colonization of empty areas. The usefulness of various measures of o verlap and s pecialization is evaluated for this lizard association.