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Hidden diversity in two species complexes of munnopsid isopods (Crustacea) at the transition between the northernmost North Atlantic and the Nordic Seas


Eurycope producta Sars, 1868 and Eurycope inermis Hansen, 1916 are two widely distributed and highly abundant isopod species complexes within Icelandic waters, a region known for its highly variable environment. The two species complexes have bathymetric depth ranges from 103 to 2029 m (E. producta) and from 302 to 2113 m (E. inermis). Molecular evidence was used for species delimitation within these species complexes by analyzing nuclear (18S rDNA, H3) and mitochondrial (16S rDNA, COI) sequence data. Tree-based methods (BI and ML) and four species delimitation methods (ABGD, GMYC, NDT, PTP) were applied, in order to disentangle the two species complexes. A total of eight and four species clades could be identified within samples of the E. producta and E. inermis complexes and respectively included the closely related species E. dahli Svavarsson, 1987; E. hanseni Ohlin, 1901; and E. cornuta Sars, 1864. The morphological findings coincide with the observed molecular species clades. The elucidated species clades were geographically and bathymetrically much more restricted than previously assumed. Eight species clades featured depth spans of less than 400 m and only four species clades featured depth spans of 1000 to 1500 m. Only two species clades (E. producta sensu stricto and E. inermis sensu stricto) were found on both sides of the Greenland-Scotland Ridge. Further, species distribution maps were generated using random forest, to predict potential distributional patterns for the resolved species clades of the two species complexes. We present the first attempt of combining morphological, molecular, and species distribution models in marine isopods thus far.

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Automated Barcoding Gap Discovery


Are We There Yet


Bayesian inference


German Centre for Marine Biodiversity Research


Generalized mixed Yule coalescent


Greenland-Scotland Ridge


Iceland-Faroe Ridge


Maximum likelihood


Nucleotide divergence threshold


Out-of-the-box error


Polymerase chain reactions


Poisson tree process


Random forest


Species distribution modeling




Zoological Museum of Hamburg


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We would like to thank the crew and participants of the IceAGE expeditions, as well as all pickers and sorters at the DZMB in Hamburg, Germany, and the Nature Centre in Sandgerði, Iceland. Special thanks go to Dr. Herman Wirshing for his help during S. Schnurr’s stays at the facilities of the Laboratories of Analytical Biology (LAB) at the Smithonian National Museum of Natural History, Washington, DC. We thank Karen Jeskulke for introducing lab workflow, Lukas Rischke for solving hardware problems, and Falk Huettmann for his introduction to random forest models.


S. Schnurr was partly funded by the German Science Foundation (DFG) under contract 2843/4-1 and BR3843/6-1, as well as by the Census of the Diversity of Abyssal Marine Life (CeDAMar), the Smithsonian’s Rathbun Fund for Crustacean Research, and the Annette Barthelt Stiftung. The IceAGE cruises were funded by the DFG contract BR3843/3-1 (IceAGE1) and 4-1 (IceAGE2).

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Correspondence to Sarah Schnurr.

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All applicable international, national, and/or institutional guidelines for the care and use of animals were followed by the authors.

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All necessary permits for sampling and observational field studies have been obtained by the authors from the competent authorities and are mentioned in the acknowledgements, if applicable.

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Communicated by K. Halanych

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Uncorrected pairwise p-distances for the 16S gene of all evaluated E. producta complex specimens. (XLSX 26.8 kb)

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Uncorrected pairwise p-distances for the 16S gene of all evaluated E. inermis complex specimens. (XLSX 33.7 kb)

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Schnurr, S., Osborn, K.J., Malyutina, M. et al. Hidden diversity in two species complexes of munnopsid isopods (Crustacea) at the transition between the northernmost North Atlantic and the Nordic Seas. Mar Biodiv 48, 813–843 (2018). https://doi.org/10.1007/s12526-018-0877-6

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  • Crustacea
  • Eurycope
  • Species complex
  • Molecular taxonomy
  • Species delimitation
  • Species distribution modeling
  • Random forest