Original paper

High species diversity and low density typify drift and benthos composition in Neotropical streams

Lobón-Cerviá, Javier; Rezende, Carla Ferreira; Castellanos, Claudia


We hypothesized that Neotropical streams might exhibit higher drift and benthos densities than their Palearctic counterparts in order to sustain the high diversity of drift-and benthos-feeding fish species that typify this vast region. We assessed drift and benthos composition in two pristine streams deemed to represent the two less documented Neotropical regions: Rio Amazonas (i.e., Yahuarcaca) and Coastal Serra do Mar (i.e., Mato Grosso). Four monthly benthos and drift samples were collected over diel cycles in the rainy and dry seasons. Although the two streams showed remarkably low drift and benthos densities, in Mato Grosso benthos density was markedly higher. The same aquatic families predominate in the drift and benthos of the two streams. High taxonomic richness, low drift density, consistent diel cycles with a peak just after dusk, higher density during the night and temporal changes unrelated to seasonality typify drift composition of the two streams. Although drift densities were lower in Yahuarcaca, the dominant families did exhibit drift behavior, with two drift peaks at night. In Mato Grosso only Baetidae showed such behavioral drift with density peaks at night; other families demonstrated passive drift. Overall, these results refute our hypothesis that Neotropical streams should exhibit higher drift and benthos densities. Actually these pristine streams show among the lowest drift and benthos density values worldwide.


invertebratesterrestrial componentsstreamsneotropicsserra do maramazonas