Summary boxplots of the 22 single-species libraries used to search the best combination of parameters γ and δ; in all cases, a detection limit of ε = 0.001 was used and contaminant species were discarded. (A) Number of identified species in the library. (B) Proportion of the assigned reads allocated to the right species. (C) Proportion of the total reads (after trimming and mapping) that were informative (i.e. assigned to any species). A different letter at the top of the figures indicates significant differences amongst γ–δ combinations.