COS 92-6 - Predaceous insects do not influence space use by anuran larvae in ponds: The role of environment and scale

Thursday, August 11, 2011: 9:50 AM
8, Austin Convention Center
Diogo B. Provete, Ecologia, Universidade Federal de Goiás, Goiânia, Brazil, Thiago Gonçalves-Souza, Department of Animal Biology, State University of Campinas, Campinas, Brazil, Denise C. Rossa-Feres, Department of Zoology and Botany, State University of São Paulo, São José do Rio Preto, Brazil and Itamar A. Martins, Departamento de Biologia, Universidade de Taubaté, Taubaté-SP, Brazil

Predation is regarded as one of the major processes shaping natural communities. Predators influence space use, behavior, abundance and richness of prey species. Previous studies demonstrated that adult anurans could access the predation risk of a breeding site and avoid laying eggs on it. Additionally, they seem to be even able to distinguish among predators according to the risk they provide. Space use by tadpoles and predaceous insects was extensively evaluated in microcosm experiments, being the results extrapolated to whole communities. Standard foraging theory predicts that predators and prey mutually avoid each other, but preys are restricted by the distribution of resources. Lima (2002) claimed that there is a necessity to evaluate the distribution of predators and preys at large spatial scales. Alternatively, the environment may influence habitat selection, since both predators and prey could be influenced by similar environmental gradients when selecting habitats and not the presence of food or predators. We accessed habitat selection by both predatory insects and tadpoles at the metacommunity level in 13 ponds in Southeastern Brazil. Specifically, we asked the following questions: (1) Are tadpoles and insects distributed non-randomly in ponds? (2) Are predators and prey selecting habitats irrespective of each other, but according to similar environmental features? We used a null model to analyze the pair-wise co-occurrence between insects and tadpoles. We used a PROTEST to test for community concordance between the tadpole-environment data, insect-environment and between the two communities. Posteriorly, we used a CCA to find main environmental gradients influencing the distribution of tadpoles and predaceous insets. 


The majority of pair-wise associations (96.3%) between tadpoles and predaceous insects was random (mean simulated C-Score + SD = 4.02+38.6), 1.1% was positive, and 2.6% of the associations were negative. The communities of tadpoles and predatory insects are concordant (r= .585; p= .015). Additionally, the two communities were influenced by similar environmental factors. Thus, environmental features are playing a major role on the spatial distribution of insects and tadpoles at the metacommunity scale. We found no predatory fish species, therefore it seems that invertebrate predators do not offer a great predation risk, sufficient to prevent oviposition by females of anurans. Indeed, studies in tropical and temperate habitats showed that tadpoles commonly co-occur with predatory insects. Habitat selection may happen in a hierarchical fashion, i.e., first females select fishless ponds to avoid egg predation and then tadpoles select safe microhabitats within the pond.

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