Contributions to Zoology, 86 (4) – 2017Kennet Lundin; Tatyana Korshunova; Klas Malmberg; Alexander Martynov: Intersection of historical museum collections and modern systematics: a relict population of the Arctic nudibranch Dendronotus velifer G.O. Sars, 1878 in a Swedish fjord

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Results

Molecular analysis of Arctic material of Dendronotus robustus and Dendronotus velifer

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The present molecular analysis shows that there are two distinct species under the name Dendronotus robustus, corresponding to D. robustus Verrill, 1870 and D. velifer G.O. Sars, 1878. Of the sampled specimens, 11 belonged to the former species and five to the latter. Minimal uncorrected p-distances for the COI gene are significantly different between both species, with a range of 8.74% ±1.24%. Distances within D. robustus group are within 0.71%. Distances within D. velifer group are up to 0.54%, but dis­tances between D. robustus and D. velifer groups reach 9.34%. Results obtained by PopART both for the COI and for 16S genes showed a network of haplotypes that clearly clustered into two groups coincident with the species D. robustus and D. velifer (Figure 4a, b).

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Figure 4. The haplotype networks (a–b) based on COI (a) and 16S (b) molecular data showing genetic mutations occurring within Dendronotus species. (c) Statistical test of the reliability of the bathymetic distribution patterns of D. robustus (blue bar) and D. velifer (red and lilac bars): comparision of the specimens involved in a molecular study (blue and red bars) with historical specimens (lilac bar) of D. velifer from Swedish and Norwegian museums. ** p<0.01, *** p<0.001. See text for details.

Statistical analysis of the bathymetric distribution

The comparison of the bathymetric distribution of specimens of Dendronotus robustus and D. velifer which were involved in the molecular taxonomic analysis (see above) reveal significant statistical differences (p=0.002, Figure 4c). The bathymetric data for historical specimens of D. velifer and for recently collected D. robustus demonstrate statistically significant differences (p <0.001, Figure 4c; right lilac and left blue bars). At the same time, the bathymetric data between historical specimens of D. velifer and the recently collected specimens of D. velifer do not show any significant differences (Figure 4c).