Ecological relationships among sympatric lizards in a transitional forest in the northern Amazon of Brazil

Abstract

Sympatric lizards in a transitional forest of Roraima, Brazil, dividing Amazon rain forest from savanna, contained a lizard assemblage of 16 species representing six families. Lizards varied in size, activity (diurnal versus nocturnal), microhabitats used, exposure to various conditions of light availability, prey types, and prey sizes. Overlaps in microhabitat occurrence varied from 0 (no overlap) to 1.0 (total overlap) whereas overlaps in prey types varied from 0.005 to 0.607. Microhabitat overlaps were higher overall than dietary overlaps. Pseudocommunity analyses on microhabitat data indicate that the community is not randomly assembled and that two distinct guilds exist, a leaf-litter guild and an arboreal guild, each with four species. Similar analyses on diet data revealed no apparent guild structure ast the first rank (nearest neighbour). Lizard diets did not differ from a random assortment based on prey type. At lower levels, the assemblage was structured with respect to food. Variation in prey use among lizard species was tied more closely to the effect of lizard body size on prey size (lizards ate different-sized prey items). Although exploitative competition among species may maintain structure within this assemblage it does not necessarily cause the observed differences. Several species are nearly identical ecologically to sister taxa in other environments and within different lizard assemblages suggesting that composition of the local assemblage limits the species that can enter the assemblage. Finally, lack of structure at the lowest (most similar) neighbour ranks may reflect the impact of a transitional habitat on stability of species interactions at the local level.