Community assembly and structure of tropical leaf-litter anurans

We tested two traditional views of community organization relating to the individualistic continuum versus the interactive concept using anuran leaf-litter assemblages in primary and secondary forest habitats in Tai National Park (TNP), Ivory Coast as a model system. Based on biotic data and species occurrence patterns, the relative importance of each of these concepts was assessed. Null model tests of niche and size overlap revealed that the observed multivariate structure was only weakly influenced by biotic interactions, and therefore is most likely not the sole result of present species interactions. Non-metric multidimensional scaling and quadratic regression analyses showed that particular species responded to certain habitat characteristics, in particular the presence or absence of specific breeding sites and tree size classes, the latter being an index of forest degradation in this case. This corresponded to a discrimination of four major functional response groups within the leaf-litter community. However, the strength of these species-specific responses, and therefore the allocation to one or other of these response groups, varied throughout the year. Thus our results indicate that differing individual life histories, rather chair interspecific interactions, were likely explanations of the observed pattern. The leaf-litter anuran assemblages of TNP can be best described as a collection of loosely interacting individuals responding to particular sets of physiological constraints imposed by a particular location, rather than as a tightly integrated and highly interacting set of species.