The additive partitioning of macroinvertebrate diversity in tropical reservoirs

Abstract. Understanding the ways in which diversity changes across spatial scales is important for the conservation of biodiversity. The objectives of the present study were (1) to characterise the diversity of aquatic macroinvertebrates in three Brazilian tropical reservoirs and (2) to determine how the organisms were distributed at different spatial scales, by using a diversity partitioning approach. We compared the diversity-partition results with the null hypothesis that the macroinvertebrate community was uniform across all spatial scales in the study. We expected that differences in environmental variability (sediment characteristics) among the reservoirs and limitations on the dispersal of organisms among reservoirs result in higher biological variability (b diversity). The results of the spatial partitioning analysis of species richness in the reservoirs showed that each Ekman–Birge dredge-sampling unit (a) represented 43.7 % of the total variation. b1 diversity (diversity among Ekman–Birge dredge-sampling units) represented 47.2 % of the total variation. A partial Mantel test indicated a correlation between the particle-size matrix and the biological matrix. However, the biological matrix was not correlated with the geographical matrix. The partitioning of overall spatial diversity indicated that the distribution of species in the reservoirs was driven by local factors and that diversitywasmore pronounced at lowe