Comparison of three hierarchical display strategies. The acid mine drainage metagenome  was classified using MG-RAST and displayed using MG-RAST, MEGAN, and Krona. MG-RAST and MEGAN augment hierarchical node-link diagrams with log-scaled, quantitative charts. Krona displays abundance and hierarchy simultaneously using a radial space-filling display. The Krona chart features a red-green color gradient signifying average e-values of BLAST hits within each taxon, with red being the highest observed e-value (least significant) and green being the lowest (most significant). An interactive version of this chart and a second chart displaying the functional classifications of the same dataset are available on the Krona website.