What influences the structure of frog assemblages at forest streams?

We investigated habitat variables influencing the species richness and composition of frog assemblages at forest streams in southeast Queensland, Australia, to (i) determine whether these assemblage attributes can be predicted from the nature of the local habitat, and (ii) assess the value of species richness as a measure of the structure of frog assemblages. Stream size (as measured by the annual volume of precipitation in the upstream catchment) was found to be a significant predictor of the species richness of an assemblage, while stream size, understorey floristics in the riparian zone, the presence of palms and elevation were significantly correlated with the composition of assemblages. No relationship was found between broad forest type and the species richness or composition of frog assemblages. Species richness was not an informative description of the composition of frog assemblages, as assemblages with identical species richness had a low average compositional similarity. Results of this study indicate that frogs are responding to local, ground-level stream and vegetation variables, a finding of both ecological interest and practical significance for the conservation management of forest-dwelling frogs.