Effects of freshwater shrimp assemblages on benthic communities along an altitudinal gradient of a tropical island stream

摘要: 1. In tropical island stream ecosystems freshwater shrimps are often the dominant macroconsumers and can play an important role in determining benthic community composition. However, most studies of ecological limited to high-altitude shrimp-dominated sites where other biota (fishes snails) absent or significantly less abundant than at lower altitudes. 2. We examined how effects different shrimp assemblages on communities changed along altitudinal gradient a Puerto Rico. We used electroshocking observations quantify abundance taxonomic composition three (300, 90 10 m a. s. l) Rio Espiritu Santo. also experimentally manipulated access environment simultaneously each site using electric fences over 35-day period. 3. At site, exclusion (predominantly Atya spp. Xiphocariselongata) resulted greater accrual organic inorganic material, chlorophyll algal biovolume. In absence shrimps, was dominated by filamentous green algae (Chlorophyta: Oedogonium Rhizoclonium). Excluding did not affect total insect biomass but increased sessile chironomids (Diptera: Chironomidae). observed similar treatment mid-altitude (primarily Macrobrachium X. elongata) occurred densities. contrast, low-altitude there were no differences a, biovolume, assemblage insects. 4. The lack probably because very high densities grazing snails (Thiaragranifera Neritina spp.) which reduced resources obscured potential effects. 5. This study demonstrates that composition; however, their vary appear depend presence biota. This suggests loss as result anthropogenic disturbances will have depending upon location altitude gradient.