INTRABIOME DISTRIBUTIONAL PATTERNS OF LOTIC MACROINVERTEBRATE ASSEMBLAGES

Macroinvertebrates were collected at five sites along each of 3 rivers within the eastern deciduous forest biome. Macroinvertebrate density at sites in mixed land use areas was intermediate between high levels at sites in farmlands and low levels in forests. Cluster analysis using mean density of the 24 dominant taxa revealed 3 groupings of river sites each of which was consistently associated with a land use type. Hydropsychidae and Leptophlebiidae characterized forested sites. The assemblage associated with mixed land use areas included Psephenidae, Baetidae, Tricorythidae, and Heptageniidae. Farmland river sites were characterized by Ceratopogonidae, Corixidae, Oligochaeta, and Tricladida. The mixed land use group of river sites was faunistically more similar to sites in forested than in farmland areas. Forested sites were fast-flowing and had little benthic detritus; farmland sites were slow-flowing and had high levels of detritus. The biome dependency hypothesis, which predicts that similar assemblages of macroinvertebrates are likely to occur at river sites both within and among drainages if the basins occupy the same biome, was not largely supported because characteristic vegetation had been disturbed. -from Author