Organization of macroinvertebrate communities at a hierarchy of spatial scales in a tropical stream

The variability of benthic macroinvertebrate (bmi) communities at three spatial scales was examined in the Juncal Stream, Coiba Island, Panama. Standard Surber samples were taken at riffle habitats of first, second and third order streams of the Juncal Stream watershed. In a nested design, we had three riffles within each stream order, and three sampling points within each riffle. Bmi total density and richness showed greater variation among stream orders and within riffles, while individual taxa varied mostly among and within riffles, and community evenness varied within riffles. Current velocity was strongly related to the variability of bmi community descriptors. Multidimensional scaling showed that first and third stream orders were more similar in bmi composition than second order. Riffles were more heterogeneous in composition within first order than within second or third orders, probably related to the greater substrate heterogeneity in first order riffles.