Results

Agreement in classification between gaugers –

The classification of the 18 pairs of independent observations made by eleven gaugers was successful for the two taxa according to the cumulative PCA analysis that involved all gaugers’ observations in the same analysis. Each gauger arrived at the two-species hypothesis with only two misidentified observations (less than 1%) out of the total 198 (Fig. 3a); a single misclassification appeared in two different gaugers respectively. The results of the PCA revealed that the species identity was responsible for the differences based on the morphological traits, and was not ascribed to gauger effect (Fig. 3b). The PCA results were based on the inertia 5489, and the variance explained by the 1st axis was 62.59%, while the variance for the 2nd axis was 10.32%; thus, the overall explained variance was 72.91%. These patterns were also revealed by the PERMANOVA performed using the Morosita index of dissimilarity with 9999 iteration, where the gaugers were shown to have no significant effect on the species identity based on the measured morphological traits (R2=0.69, p=0.58).