Two tropical biodiversity hotspots, two different pathways for energy

Abstract

Abstract Local factors, such as riparian vegetation and stream type, affect the structure and composition of benthic macroinvertebrate assemblages in streams. To better understand the effects of biomes on lotic ecosystems, we evaluated whether Atlantic Forest (AF) and Neotropical Savanna (NS) biomes showed distinct patterns in (i) benthic macroinvertebrate assemblage structure and (ii) the shredder functional feeding group. We predicted that (i) richness, density, biomass, instant secondary production, eco-exergy, and specific eco-exergy would be higher for benthic macroinvertebrate assemblages in AF stream sites than in NS sites. We also predicted that (ii) length, density, biomass, instant secondary production, eco-exergy, and specific eco-exergy would be higher for shredders in AF stream sites. We found that benthic macroinvertebrate assemblage composition and taxa richness were significantly different between stream sites in the two biomes, with the AF biome being the richest. But we found no differences in density, biomass, instant secondary production, eco-exergy, or specific eco-exergy between AF and NS stream sites. For AF shredders, the mean length, density, biomass, secondary production and eco-exergy were significantly higher than for NS stream sites. These differences were attributed to the quality of leaf litter, which was generally higher in AF than in NS stream sites. This indicates that the intrinsic characteristics of the AF and NS biomes act as structuring factors for benthic macroinvertebrate assemblages, influencing the structure and functioning of tropical lotic ecosystems.