Assessing the spatial variation of functional diversity estimates based on dendrograms in phytoplankton communities

Abstract

Variation in phytoplankton functional diversity is partioned and mapped using several indices and linkage methods based on dendrograms. Th e relationships between diversity metrics and major environmental predictors, including zooplankton density, were assessed in 29 phytoplankton communities of fl oodplain lakes distributed along the Middle Araguaia River in central Brazil. Th e dendrogram-based functional diversity indices were Functional Group Richness, Functional Diversity, Mean Pairwise Distance and Mean Nearest Taxon Distance, whereas seven diff erent hierarchical agglomerative linkage methods we used. Th e performance of indices were compared using ANOVA and their spatial variation in response to major environmental predictors evaluated. Th e results indicate that variation in functional diversity values is primarily a product of the type of index chosen. Th is variation was statistically signifi cant in 90 % of the fl oodplain 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. Th erefore, the mathematical characteristics of indices are of primary importance in explaining variation among functional diversity values.