Biodiversity of arctic marine fishes: taxonomy and zoogeography
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Taxonomic and distributional information on each fish species found in arctic marine waters is reviewed, and a list of families and species with commentary on distributional records is presented. The list incorporates results from examination of museum collections of arctic marine fishes dating back to the 1830s. It also incorporates results from DNA barcoding, used to complement morphological characters in evaluating problematic taxa and to assist in identification of specimens collected in recent expeditions. Barcoding results are depicted in a neighbor-joining tree of 880 CO1 (cytochrome c oxidase 1 gene) sequences distributed among 165 species from the arctic region and adjacent waters, and discussed in the family reviews. Using our definition of the arctic region, we count 242 species with documented presence, if 12 species that likely are synonyms are excluded. The 242 species are distributed among 45 families. Six families in Cottoidei with 72 species and five in Zoarcoidei with 55 species account for more than half (52.5%) the species. This study produced CO1 sequences for 106 of the 242 species. Sequence variability in the barcode region permits discrimination of all species. The average sequence variation within species was 0.3% (range 0–3.5%), while the average genetic distance between congeners was 4.7% (range 3.7–13.3%). The CO1 sequences support taxonomic separation of some species, such as Osmerus dentex and O. mordax and Liparis bathyarcticus and L. gibbus; and synonymy of others, like Myoxocephalus verrucosus in M. scorpius and Gymnelus knipowitschi in G. hemifasciatus. They sometimes revealed the presence of additional species that were not entirely expected, such as an unidentified species of Ammodytes in the western Gulf of Alaska, most likely A. personatus; and an unidentified Icelus species of the I. spatula complex with populations in the western Gulf of Alaska and the northern Bering and Chukchi Seas which could be a new species or a species in synonymy. Reviewing distribution, we found that for 24 species the patterns assigned by authors understated historical presence in the arctic region, and for 12 species they overstated presence. For instance, Hippoglossoides robustus is counted as an arctic–boreal species rather than predominantly boreal, and Artediellus uncinatus as predominantly arctic rather than predominantly boreal. Species with arctic, predominantly arctic, or arctic–boreal distributions composed 41% of the 242 species in the region, and predominantly boreal, boreal, and widely distributed species composed 59%. For some continental shelf species, such as the primarily amphiboreal Eumesogrammus praecisus and Leptoclinus maculatus, distributions appear to reflect changes, including reentry into Arctic seas and reestablishment of continuous ranges, that zoogeographers believe have been going on since the end of land bridge and glacial times.