Figure 3. Observed versus expected background abundances (0.1–5%) for all symbiont types using ITS-2 454 NGS.

Observed values were calculated by dividing the number of mapped reads retrieved per sample by the total number of reads retrieved for that symbiont type in that sample and multiplying by 100 (grey points). The mean value for each expected abundance and its 95% bootstrap confidence interval are shown in black. Background abundance estimates for symbiont types C1, A13, and D1 were strongly correlated to expected abundances (gamma = 0.76–0.90). However, the gamma correlation coefficient for C3 was 0.44, with a corresponding non-significant p-value.