Citation:

Macedo, D., R. Hughes, R. Ligeiro, W. Ferreira, M. Castro, N. Junqueira, D. Oliveira, K. Firmiano, Phil Kaufmann, P. Pompeu, AND M. Callisto. The Relative Influence of Catchment and Site Variabbles on Fish and Macroinvertebrate Richness in Cerrado Biome Streams. LANDSCAPE ECOLOGY. Springer, New York, NY, 29(6):1001-1016, (2014).

Impact/Purpose:

Indices of biointegrity that employ fish and macroinvertebrate assemblage richness in their formulation are increasingly becoming the tools of choice for assessing the impacts of human activities on flowing waters worldwide. However, the relationship between richness and human disturbance is not a simple one. Even in the absence of human disturbances, the numbers of fish and macroinvertebrate taxa differ among geoclimatic provinces, ecoregions, basins, and with local habitat variation among streams. Macedo and co-authors, using USEPA NARS stream survey designs and field methods in two large basins within the Cerrado biome of Brazil, compared the strength of associations between biotic richness and three types of predictors: anthropogenic stresses, natural landscape attributes, and instream & riparian physical habitat. They found that macroinvertebrate richness was more predictable than fish assemblage richness. They demonstrated, for both types of assemblages, the general level of human disturbance in a basin influenced the degree to which natural habitat variability explained taxa richness, a finding that has important implications for biomonitoring studies. Furthermore, their results indicated that even in the same biome, fish and macroinvertebrate assemblages responded differently to the same sets of predictor variables, and that combinations of natural landscape, physical habitat, and human disturbance pressure metrics yielded the most precise predictions. These results indicate that the sufficiently comprehensive landscape, disturbance and physico-chemical data should be collected in association with biotic data in order to effectively assess human impact on biodiversity and biointegrity.

Description:

Landscape and site-scale data aid the interpretation of biological data and management alternatives. We evaluated how three classes of environmental variables (natural landscape, anthropogenic pressures, and local physical habitat), influence fish and macroinvertebrate assemblage richness in two basins in the Brazilian Cerrado biome. We analyzed our data through use of multiple linear regression models (MLR) using the three classes of predictor variables alone and in combinations. The three MLRs built for the Araguari Basin explained similar amounts of benthic macroinvertebrate richness (natural landscape R2=54%, anthropogenic pressures R2=58%, physical habitat R2=60%) and the combined model 73%. In the São Francisco Basin, the three MLRs explained less of the macroinvertebrate richness (natural landscape R2=25%, anthropogenic pressures R2=32%, physical habitat R2=46%) and the combined model 50%. The MLRs built to explain fish species richness were weaker and less similar than those for macroinvertebrates. In the Araguari Basin, natural landscape, anthropogenic pressures, and physical habitat variables respectively explained 32%, 20%, and 45% of fish species richness and the combined model 64%. In the São Francisco Basin, natural landscape, anthropogenic pressures, and physical habitat variables explained 25%, 10%, and 36% of the variability in fish species richness, respectively, and the combined model 47%. We conclude that different basins in the same biome differ in the degree to which different sets of landscape and site variables explain assemblage richness, that landscape and site variables explain more variability in macroinvertebrate richness than in fish richness, and that both landscape- and site-scale variables are useful for explaining assemblage richness in Cerrado headwater streams.

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