Correction to: Morphological and taxonomic demarcation of Brachionus asplanchnoidis Charin within the Brachionus plicatilis cryptic species complex (Rotifera, Monogononta)

Correction to: Hydrobiologia (2017) 796:19–37 https://doi.org/10.1007/s10750-016-2924-2

The authors of the original publication recognized that, for three of the clones (MAN-L5, LFL2, KOR), the data of two of the raw morphometric measurements contained in Supplementary Material 2 of the article were flipped (the distance between the anterior tips of the 3rd dorsal spines ‘b’ and the width of the lorica ‘c’). The corrected Supplementary material 2 is provided here. As a consequence, the principal components analysis (PCA) and discriminant analysis (DA) were repeated, and the corrected version of Fig. 3, Tables 4, 5, 6 and 7 are also provided here.

Fig. 3

Analysis of the association between species delimitation and morphometry. A Representation of sample score averages of each of the studied clones along the first two axes of the principal components analysis (PC1 explained 71.14% and PC2 explained 8.89% of the recorded variation) performed on the morphometric data. Error bars represent variation between individuals of the same clone (twice the standard error of the mean). B Scatterplot showing the discrimination of species groups based on the canonical discriminant functions of the discriminant analysis performed on all measured individuals. Error bars represent variation between individuals of the same clone (twice the standard error of the mean). C Distribution of the number of individuals of Brachionus asplanchnoidis and the rest of the L group members along the discriminant axis obtained from morphometric data. The bars shown under the x axis do not represent negative values. D Box-and-whisker plot of r (width of the medial sinus of the anteroventral margin) for the four species ASP, Brachionus asplanchnoidis; PLI, B. plicatilis; MAN, B. manjavacas; NEV, B. ‘Nevada’

Table 4 Stepwise discriminant analysis of the Brachionus body measurements

Table 5 Classification functions of the stepwise discriminant analysis

Table 6 Measurements (in μm) (range, mean, St. Error) of the dimensions of the individuals that have been used for the morphometric analysis

Table 7 Results of ANOVA and post hoc Fisher LSD test for differences in lorica measurements identified as discriminating traits between the four species of Brachionus plicatilis cryptic species complex

PCA explains a similar amount of the observed variation (PC1 71.14%, PC2 8.89%) and still clearly separates the clones of B. asplanchnoidis from the rest of the members of the L clade, revealing however a great degree of morphometric variability within the B. asplanchnoidis members (Fig. 3A). DA performed on the phylogenetically identified species also clearly separates B. asplanchnoidis from the rest of the species (Fig. 3B). Table 4 shows the results of the discriminant analysis where the classification factor was the four species of the L clade. Classification Functions 1 and 2 accounted for a similar amount of the total variance, 78.3% and 16.2%, respectively, revealing mainly two groups (Wilks’ Lambda = 0.454, χ² = 158.61, df = 14, P < 0.001) (Fig. 3B). The variables weighting the most in the classification function 1 were the width of the medial sinus of the anteroventral margin (r) and the width of the lorica (c) (see correlation coefficient in Table 4). Cross-validation of the individuals’ classification based on the classification functions (Table 5) of the discriminant analysis correctly identified 96.6% B. asplanchnoidis individuals. Still, for the two groups, i.e., one group B. asplanchnoidis clones and the other group B. plicatilis, B. manjavacas, and B. ‘Nevada’ clones, identified in the discriminant analysis, some overlap was recorded of the scores of the discriminant functions (Fig. 3C). All measurements (Supplementary Material Table 2) covered a wide range of values within each species and exhibited great overlap (Table 6), while most of them differed significantly between species (Table 7). From the morphological analysis, the differences between B. asplanchnoidis and the rest of the representatives of the L clade concern the anteroventral margin which is more pronounced in the case of B. plicatilis (Fig. 3D). In B. asplanchnoidis, the medial sinus is much deeper and wider compared to B. plicatilis (r range 20–51 μm and 5–23 μm, respectively).

The main conclusions of this study remain the same. Brachionus asplanchnoidis differs compared to the rest of the representatives of the L clade of the B. plicatilis complex based on the medial sinus of the anteroventral margin, which is more pronounced in the case of, e.g., B. plicatilis (Fig. 3D). In B. asplanchnoidis, the medial sinus is much deeper and wider (r range 20–51 μm) compared to B. plicatilis (r range 5–23 μm). Furthermore, the structured orange peel-like surface is more closely spaced and less pronounced in B. asplanchnoidis compared to B. plicatilis (Fig. 5B, C). Nevertheless, as already pointed out by Fontaneto et al. (2007), the observed morphological differences are greater among the size clades of the B. plicatilis cryptic species complex than within each size group.