255 Effects of environmental and spatial factors on the distribution of anuran species with aquatic reproduction in central Amazonia M. Menin 1,3 , F. Waldez 2 & A.P. Lima 2,3 1 Departamento de Biologia, Instituto de Ciências Biológicas, Universidade Federal do Amazonas, Manaus, Brazil 2 Coordenação de Pesquisas em Ecologia, Instituto Nacional de Pesquisas da Amazônia, Manaus, Brazil 3 Instituto Nacional de Ciência e Tecnologia de Estudos Integrados da Biodiversidade Amazônica, Ministério da Ciência e Tecnologia, Conselho Nacional de Desenvolvimento Científico e Tecnológico – INCT-CENBAM/MCT/CNPq, Brazil We evaluated the effect of environmental and spatial variables on the distribution of 11 species of anurans in 10,000 ha of non- flooded forest in central Amazonia. Diurnal and nocturnal frog assemblages were sampled in 72 plots using visual and auditory surveys. Distance from stream was the best predictor for species richness and abundance, with an increase in distance resulting in a decrease in number of species and individuals. Three species (Osteocephalus oophagus, Trachycephalus resinifictrix and Vitreorana oyampiensis) were not influenced by environmental predictors and occurred along all environmental gradients. The watersheds did not influence the abundance of the majority of species except Allobates sp., Atelopus spumarius and Leptodactylus rhodomystax. Our results indicate that most species studied occur along the margins of streams, which they also use as dispersal corridors. The removal of forests near streams could lead to local extinctions. Key words: Anura, abundance, Brazil, community structure, distribution pattern, environmental factors HERPETOLOGICAL JOURNAL 21: 255–261, 2011 Correspondence: Marcelo Menin, Departamento de Biologia, Instituto de Ciências Biológicas, Universidade Federal do Amazonas, Av. General Rodrigo Otávio Jordão Ramos 3000, 69077-000, Manaus, Amazonas, Brazil. E-mail: menin@ufam.edu.br INTRODUCTION S tudies relating the distribution and diversity of an- urans with environmental variables in tropical forests have often been based on litter communities on the for- est floor (Fauth et al., 1989; Allmon, 1991; Giaretta et al., 1999). Topographic factors such as altitudinal vari- ation (Giaretta et al., 1999) and edaphic factors such as pH (Wyman, 1988), humidity (Vonesh, 2001), type of soil (Hadden & Westbrooke, 1996), clay content (Menin et al., 2007) and leaf litter (Fauth et al., 1989) are the major factors influencing the distribution of many terrestrially breeding anurans. The composition of the assemblage of adults and tadpoles associated with riparian zones, on the other hand, is largely influenced by characteristics such as understory vegetation, stream size, slope and predation (Parris & McCarthy, 1999; Eterovick & Barata, 2006; Keller et al., 2009). The composition of such assemblages differs between areas, contributing to high overall anuran species richness and high species turnover between sites (Keller et al., 2009). Studies conducted in central Amazonian forests that focused on riparian areas concluded that the distribu- tion of anuran species is mainly affected by the presence of suitable breeding sites (Zimmerman & Bierregaard, 1986; Zimmerman & Simberloff, 1996). Terrestrially re- producing anurans are widely distributed along a range of environmental gradients, showing small beta diversity probably because of few constraints on dispersal (Menin et al., 2007). In a study in Atlantic forest in Brazil, species were dependent on the connectivity between forests and the presence of aquatic sites for reproduction, suggesting a differential distribution of adults during non-reproduc- tive periods (Becker et al., 2007). In the Amazon forest, the development of eggs and tadpoles of aquatically breeding species takes place mainly in temporary ponds near streams, isolated ponds on plateaux far from streams, in accumulated water in tree holes, bromeliads, palm leafs or bamboo internodes, or directly in streams (Hödl, 1990; Summers & McKeon, 2004; Lima et al., 2006). Aquatic-reproducing anurans use rather specific breeding sites, because the presence of their larvae depends on predator densities, hydroperiod of the water body, reproductive modes and the susceptibility of eggs to desiccation (Duellman & Trueb, 1994; Pear- man, 1997; Hero et al., 1998; Both et al., 2010; Rodrigues et al., 2010). Riparian zones are defined as the area around the mar- gins of water bodies susceptible to flooding (Gregory et al., 1991), and can show differential composition in taxo- nomic groups such as terrestrial herbs. Plant composition along the margins of large rivers contributes to variation in beta-diversity between habitats (Ferreira, 2000; Sabo et al., 2005). Riparian environments are complex, because flooding patterns, water and litter accumulation and light availability in the understory can change rapidly in space and time (Drucker et al., 2008). In a terra firme forest in central Amazonia, 42 species of anurans have been re- ported, of which 28 deposit their eggs in aquatic sites in riparian zones or have an aquatic larval stage (Zimmer- man & Simberloff, 1996; Lima et al., 2006). We studied the distribution of aquatic-reproducing anurans in 72 plots systematically distributed in an area of 64 km 2 , involving locations near and distant from water bodies. We consid- ered the species using three breeding sites: 1) streams, 2) ponds and 3) phytotelmata. We determined first, the role of biotic and abiotic factors in the abundance and occurrence of anuran species, and second, the pattern of