AUC values and 95% bootstrap confidence intervals (in brackets) obtained in the discriminatory analysis of methods for sampling completeness quantification.

NPE is the proportion of species richness out of the total predicted by a non-parametric estimator (Jacknife) [57]; STE is Mao Tau estimator [41], [61]; FIDEGAM is the first derivate of a GAM with Poisson response fitted to species accumulation curves. The analyses were repeated in two scenarios of high and low levels of sampling exhaustiveness (from the ORDESA and SIMULAUsub databases, respectively), and in an ideal situation where the true species richness was known (SRtrue). Grading guidelines for AUC values indicate fail (0.50–0.60), poor (0.60–0.70), fair (0.70–0.80), good (0.80–0.90) and excellent (0.90–1.00) discrimination.