| Summary: | ABSTRACT Variation in phytoplankton functional diversity is partioned and mapped using several indices and linkage methods based on dendrograms. The relationships between diversity metrics and major environmental predictors, including zooplankton density, were assessed in 29 phytoplankton communities of floodplain lakes distributed along the Middle Araguaia River in central Brazil. The dendrogram-based functional diversity indices were Functional Group Richness, Functional Diversity, Mean Pairwise Distance and Mean Nearest Taxon Distance, whereas seven different hierarchical agglomerative linkage methods we used. The performance of indices were compared using ANOVA and their spatial variation in response to major environmental predictors evaluated. The results indicate that variation in functional diversity values is primarily a product of the type of index chosen. This variation was statistically significant in 90 % of the floodplain lakes studied; however, a spatial pattern of variation in index values along the river was not detected. Furthermore, environmental constraints, including zooplankton density, were weak predictors of functional diversity indices. Therefore, the mathematical characteristics of indices are of primary importance in explaining variation among functional diversity values.
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