Classifications using relative abundance data. (a) Optimal number of clusters for five strategies in R package clValid; see http://cran.r-project.org/web/packages/clValid/vignettes/clValid.pdf for details. Silhouette width (Kaufman and Rousseeuw [24] measures the difference between the distance of the site to the nearest-neighbor group and its distance from others in the same group. The higher the index is on the −1 to +1 scale the better is the site classified. (b) Silhouette plot of fuzzy classification using function fanny(); four groups specified, euclidean metric. Agglomerative classification with function agnes(). Euclidean metric, Ward cluster strategy. Agglomerative coefficient = 0.92. (d) Consensus hierarchical classification that synthesizes dendrograms produced by Ward, single, complete, average, mcquitty, median, and centroid cluster methods; see http://cran.r-project.org/web/packages/clue/vignettes/clue.pdf for detail.