Effect of size-sorting and tissue preparation on individual read abundance. A, C, E show read abundances (logarithmic scale) per operational taxonomic unit (OTU) resulting from two different metabarcoding approaches (orange – purified DNA extracts, blue – direct PCR) with varying (2A) or equal (2C, E) mass per specimen from two different mock communities (Mock A, n = 5; Mock B, n = 3). Dots represent read abundances; means and ranges are indicated by vertical lines. B, D, F show boxplots illustrating variation in read abundance within mocks and within OTUs. Variation in read abundance is calculated as standard deviation of the compared values. The lower and upper hinges of boxplots correspond to the first and third quartiles. The upper whisker extends from the hinge to the largest value no further than 1.5 times the inter-quartile range from the hinge. The lower whisker extends from the hinge to the smallest value at most 1.5 times the inter-quartile range from the hinge. Data beyond the end of the whiskers, i.e., outliers, are plotted individually.