Similar diets in two syntopic lizard species (Squamata: Teiidae) from an island in northeastern Argentina

How coexisting species partition resources is a central focus of ecology, and diet is an important potential axis of competition. Here, we study the diet of syntopic populations of the lizards Ameivula apipensis and Teius oculatus from an island in northeastern Argentina. Based on stomach contents extracted from specimens collected in September and December 2012 and February 2013, we analyzed prey richness and abundance and calculated both trophic niche breadth and the degree of dietary overlap for the two species. Both species were almost completely insectivorous, and their dietary composition showed a similar prey richness. Numerically, Isoptera dominated the diet of both species, followed by Hymenoptera, insect larvae, and Coleoptera. We report a low niche breadth for each species and substantial overlap between them. This high overlap in their diets could reflect the overall abundance of prey resources in the environment. Other factors, such as the foraging microenvironment and activity period, might be dimensions on which the niches of these species are differentiated.