Limnetica 38

Our aim was to determine the spatial (edge and center) and taxonomic influences of macrophyte beds of two species, Diamantina lombardii and Eriocaulon aquatile, on attributes, structure and functional feeding groups (FFG) of macroinvertebrate in a Brazilian savanna stream. A total of 29 invertebrate taxa were sampled, with the families Simuliidae and Chironomidae being most abundant. Diamantina lombardii exhibited greater density and richness of macroinvertebrates (2191 ind/g and 13 taxa, respectively) than E. aquatile (1217 ind/g and 8 taxa, respectively), which can be attributed to differences in leaf morphology (different resource and habitat availability). The habitat provided by D. lombardii favors better protection from the force of water current, which increases habitat dependence and facilitates macroinvertebrate colonization, whereas E. aquatile exhibited a greater number of exclusive taxa. Higher macroinvertebrate density also increased prey density, thereby explaining the greater abundance of predators found, mainly in the edge (by predation facilitation). Furthermore, spatial site in macrophyte beds can drive the composition of FFG by determining the availability and type of food resources. Filtering-collectors (25 %) remove fine particles of organic matter from the water column, which explains their greater abundance at the edge of the beds. Gathering-collectors (45 %) consume organic matter obtained from the substrate and thus do not require water flow, which explains their greater density in the center of the beds. Therefore, macrophyte beds are important habitats that need to be conserved for the maintenance of macroinvertebrate biodiversity in Savannah streams.