Using environmental and spatial filters to explain stonefly occurrences in southeastern Brazilian streams : implications for biomonitoring

Abstract

Many biomonitoring programs of aquatic systems are based on knowledge of species geographic distributions and on how different groups respond facing different sources of impact. In this study, we asked if plecopteran occurrences at genus level can be explained using environmental conditions of low-order Southeastern Brazilian streams. Additionally, we asked if plecopteran nymphs discriminate reference streams from streams under diffuse anthropic impacts. We sampled plecopteran nymphs in 44 first- and second-order reference streams and in 14 test streams representing three of the most common land uses in the State of São Paulo (Eucalyptus, sugar-cane plantation and pasture). Our data set included incidence of Plecoptera genera, and genus richness as response variables, and environmental and spatial variables as predictors. We adopted a variation partitioning technique and estimated the unique and common effects of the two sets of explanatory variables on the response variables using multiple regression and RDA analyses. We found no relation between our response variables and environmental factors. Our results also revealed that only spatial variables significantly explained the variation on distributional patterns of Plecoptera in reference streams. This result seems to characterize differences between mountain areas and the sedimentary basin. Defining regions and reference streams for biomonitoring is an essential step to establish effective biomonitoring in the State of São Paulo, because it may contribute to separate natural variability from anthropogenic influences.

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