Temporal dynamics of zooplankton richness.

<p>Shown are the time series for each zooplankton group and for the different sampling sites (Ribeirão das Lajes Reservoir; Brazil).</p

Predicting temporal variation in zooplankton beta diversity is challenging

<div><p>Beta diversity, the spatial variation in species composition, has been related to different explanatory variables, including environmental heterogeneity, productivity and connectivity. Using a long-term time series of zooplankton data collected over 62 months in a tropical reservoir (Ribeirão das Lajes Reservoir, Rio de Janeiro State, Brazil), we tested whether beta diversity (as measured across six sites distributed along the main axis of the reservoir) was correlated with environmental heterogeneity (spatial environmental variation in a given month), chlorophyll-<i>a</i> concentration (a surrogate for productivity) and water level. We did not found evidence for the role of these predictors, suggesting the need to reevaluate predictions or at least to search for better surrogates of the processes that hypothetically control beta diversity variation. However, beta diversity declined over time, which is consistent with the process of biotic homogenization, a worldwide cause of concern.</p></div

Pairwise Pearson’s correlation coefficients between beta diversity measures estimated for zooplankton communities in Ribeirão das Lajes Reservoir.

<p>βBC: average of the Bray-Curtis dissimilarity matrix; dBC: average distance to group the centroid group; βRC: modified Raup-Crick index; βSØR: Sørensen multiple site dissimilarity index; βSIM: Simpson multiple site dissimilarity index; βNES: Nestedness component; BD total: total beta diversity.</p

Study area (Ribeirão das Lajes Reservoir, municipality of Piraí, Rio de Janeiro State).

<p>The location of the sampling sites is also shown (L1: riverine region; L2, L3 and L4: transition region; L5: arm near the lacustrine region; L6: lacustrine region, near the dam).</p

Temporal variation of zooplankton beta diversity at Ribeirão das Lajes Reservoir, Brazil.

<p>dBC: average distance to group centroid; βRC: modified Raup-Crick index; βSØR: Sørensen multiple site dissimilarity index; βSIM: Simpson multiple site dissimilarity index; βNES: Nestedness component, βBC: average of the Bray-Curtis dissimilarity matrix; BD total: total beta diversity. The horizontal line indicates the results expected by chance (for βRC).</p

GLS models incorporating different autocorrelation structures (assuming no autocorrelation (OLS), ARMA(1,0) and (ARMA(2,0)) for zooplankton beta diversity (dBC and βNes) at Ribeirão das Lajes Reservoir, Brazil.

<p><i>SE</i> = Standard Error; dC Env = Environmental heterogeneity; dBC: average distance to the centroid group; βNES: Nestedness component.</p

Temporal dynamics of zooplankton abundance.

<p>Shown are the time series for each zooplankton group and for the different sampling sites (Ribeirão das Lajes Reservoir; Brazil).</p