Background
    Gadids comprise more than 50 species in 21 genera,
        arranged as three subfamilies
         Gadinae (cods & pollocks)
         Lotinae (burbot)
         Phycinae (hakes)

    Gadines are an important commercial groups
            cod, pollock, whiting, haddock

    The Grand Banks cod fishery

    Predominantly North Atlantic: whence four endemic Pacific species?
            Pacific cod (Gadus macrocephalus)
            Alaska pollock (Theragra chalcogramma)
            Pacific tomcod (Microgadus proximus)
            Saffron cod (Eleginus gracilis)

Methods
    Dorothy Crutcher, BSc hons; Dave Kivlichan, BSc hons; Pierre Pepin [PhD], Heather Warren, BSc hons
    Collecting localities
    mitochondrial DNA (mtDNA): cytochrome b & cytochrome oxidase I = 896bp
       "... a small, circular molecule"
    Phylogeny reconstruction:
       cladistic: least # changes
       distance: shortest tree
       likelihood: least improbable

Results
    (1) Eastern Atlantic pouts & poutings (Trisopterus spp.)
             Sister group to the remaining taxa
    (2) Tomcod (Microgadus spp.) + arctic Navaga & Pacific Saffon cod (Eleginus spp.)
            But, Eleginus more close related to Pacific than either is to Atlantic tomcod
    (3) Haddock + Whiting (Melanogrammus & Merlangius)
    (4) Codfish (Gadus spp.) + Arctic cod (Boreogadus) + Alaskan pollack (Theragra)

Discussion: Nomenclatorial & Biogeographic implications

    Greenland Cod
       sympatric with Atlantic cod (G. morhua)
       But: mtDNA identical to Pacific cod: synonymize with G. macrocephalus (Gadus ogac)
                northward & eastward range extension

    Gadus, Boreogadus, & Theragra unresolved
          Alaska Pollock (Theragra) an independent Pacific invasion?

    Microgadus paraphyletic: includes Eleginus
        Pacific tomcod (Microgadus proximus) is endemic to Pacific: third invasion
        Saffron Cod (Microgadus [Eleginus] gracilis) a fourth Pacific invasion

    Morphological perspectives
       Svetovidov (1948) key to gadid genera
       Dunn (1989) cladistic analysis of morphology & osteology
       morphology versus molecules

Conclusions

     Three (or more) parallel Pacific radiations
        simultaneous, 3.0 ~ 3.5 MYBP:  Bering Strait re-opens
    Greenland cod = Pacific Cod (G. macrocephalus): north- & eastward range extension
    Microgadus includes Eleginus

At Memorial University, we are working to expand this study to include other genera of gadiform fishes.