Antipredator defenses influence the distribution of amphibian prey speciesin the central Amazon Rain Forest

The high diversity of amphibians in the central Amazon Rain Forest allowed us to examine the influence of tadpole antipredator defenses on assemblage structure and composition within bodies of water (alpha diversity) and amon g aquatic sites (beta diversity) at a local scale. During a three-year stud y of tadpole assemblage composition, we found that the anuran community use d a variety of bodies of water for reproduction; these ranged from streams and streamside ponds to isolated forest ponds. The distribution of several tadpole species was negatively related to fish density, while other species coexisted with high densities of fish. Tadpole size did not ensure surviva l against fish, and few tadpoles avoided fish by hiding in the leaf litter. Controlled predation experiments using a single tadpole species in a no-ch oice situation were conducted over 24- to 48-hour periods. Nearly al specie s of tadpoles that occurred in habitats with high fish densities were unpal atable to fish (except Centrolenella oyampiensis), indicating that unpalata bility is a major adaptation allowing tadpoles and fish to coexist in this system. Unpalatability (to fish), however, was nor an effective antipredato r defense against odonate larvae, the other major tadpole predator in this system. The combination of predation pressure and the antipredator traits e xhibited by individual species largely determined the composition of tadpol e assemblages in individual bodies of water (alpha diversity). The heteroge neous distribution of predators among bodies water and the diversity of ant ipredator defenses exhibited by larva amphibians facilitated high diversity in this community (beta diversity).