Tree Buttress Microhabitat Use by a Neotropical Leaf-Litter Herpetofauna STEVEN M. WHITFIELD 1 AND MAYA S. F. PIERCE The Evergreen State College, Olympia, Washington 98505, USA ABSTRACT .—We assessed the importance of tree buttresses as a microhabitat for leaf-litter amphibians and reptiles in a tropical wet forest in Costa Rica by making comparisons of species richness and abundance between pairs of 4 3 4 m leaf-litter quadrats. One quadrat in each pair contained a central buttressed tree, and the other did not. Both abundance and species richness of the herpetofauna were much greater in plots containing buttressed trees; higher species richness in buttress plots was attributed solely to greater abundance in these plots. Buttress and nonbuttress plots contained a similar species composition, and we found particularly strong use of this microhabitat by the scincid lizard Sphenomorphus cherriei. Our results indicate that the microhabitat provided by tree buttresses forms a site of generalized high abundance for the leaf-litter herpetofauna and may contribute to localized high abundance of at least one species. Ecological and evolutionary factors contribut- ing to the maintenance of high biodiversity in tropical ecosystems are a source of great interest to ecologists and a topic of much debate (Pianka, 1966; Stevens, 1989; Colwell and Hurtt, 1994; Rosenweig, 1995; Huston, 1999; Gaston, 2000). Although numerous potential explana- tions have been implicated in trends in latitudi- nal species gradients, one suggestion holds that greater spatial heterogeneity on the scale of microhabitats may lead to greater niche di- versification in tropical regions (Pianka, 1986; Tokeshi, 1999). Microhabitats often play an important role as resources that are partitioned between phyloge- netically or ecologically similar species (Scho- ener, 1974; Toft, 1985; Vitt and Zani, 1996). Buttressed roots that flare from the base of large trees form a distinctive characteristic of tropical forests, and it has been repeatedly suggested that buttresses serve as an important microhabitat for many species of leaf-litter amphibians and reptiles (Heyer and Berven, 1973; Voris, 1977; Lieberman, 1986). Heyer and Berven (1973) compared species diversity of amphibians and reptiles found in tree buttresses in rain forests from Ecuador and Thailand but did not compare species composi- tion surrounding buttresses to that of the community as a whole. Voris (1977) attempted a comparison of diversity in buttress micro- habitats to diversity in the community as a whole and suggested that several species were ‘‘buttress specialists’’ because they were only found in the immediate vicinity of buttressed trees. These studies suggest the possibility that tree buttresses serve as an important microhabitat for niche differentiation and may play a role in the maintenance of high diversity in tropical forests. Although Voris’ sampling of the fauna around buttresses was systematic and quantitative, his whole community sampling was casual and did not include systematic searches of leaf-litter microhabitats. It has been suggested that, as opposed to microhabitat specialization on tree buttresses, accumulations of leaf-litter surrounding but- tresses may account for greater abundance of amphibians and reptiles around buttressed trees (Heyer and Berven, 1973; Voris, 1977). Numer- ous studies have detected a relationship be- tween leaf-litter depth and abundance of leaf- litter amphibians and reptiles (Heyer and Berven, 1973; Scott, 1976; Lieberman, 1986; Fauth et al., 1989; Allmon, 1991; Heinen, 1992), yet quantitative comparisons of litter depth between buttresses and the forest floor in general are lacking. If tree buttresses serve as an important microhabitat in shaping leaf-litter amphibian and reptile communities by microspatial niche differentiation, then we expect to find species that occur nearly exclusively within this micro- habitat and not within the leaf-litter matrix as a whole. If amphibians and reptiles are merely responding to increased litter depth between buttresses, then we expect to find greater abundance of amphibians and reptiles surround- ing tree buttresses and similar species composi- tion representative of the entire leaf-litter herpetofauna. In this study, we attempt to clarify the role of buttresses in structuring amphibian 1 Corresponding Author. Present address: Florida International University, Department of Biological Sciences, UP Campus, OE 167, Miami, Florida 33199, USA; E-mail: steven.whitfield@fiu.edu Journal of Herpetology, Vol. 39, No. 2, pp. 192–198, 2005 Copyright 2005 Society for the Study of Amphibians and Reptiles