Mitochondrial cytochrome b DNA sequence variation of Atlantic cod Gadus morhua, from Norway

Abstract

We studied sequence variation of a fragment of the mitochondrial cytochrome b gene using polymerase chain reaction (PCR) and direct sequencing among 85 Norwegian Atlantic cod Gadus morhua, from nine sampling localities representing three overall areas: arctic, coastal and middle. In the analysis we include an additional 15 cod studied by Carr & Marshall (1991a). Nine base changes were found among the 100 sequences defining 11 haplotypes which differ from each other by one to five mutations. Two sites have been hit twice. All but one mutation are at third position silent sites. The variation passes several neutral‐theory tests and is thus suitable as marker for studying population differentiation. Coefficients of coancestry or intraclass correlation coefficient are negative both at the level of individuals within localities and localities within areas. This implies greater differences among individuals within populations than between populations. Intralocality nucleotide diversity is high and masks interlocality nucleotide divergence such that the net interlocality nucleotide divergence is nil. Similarly the net interarea nucleotide divergence is nil.

Phylogeographic mitogenomics of Atlantic codGadus morhua: Variation in and among trans‐Atlantic, trans‐Laurentian, Northern cod, and landlocked fjord populations

“…(2007) claimed strong evidence of isolation by distance, but included only one Northwest Atlantic population (from the Scotian Shelf) whose closest geographic neighbor was from Greenland. Analyses with short mtDNA cytochrome b sequences (307–401 bp) alone consistently suggest an absence of genetic differentiation within regions and trans‐Atlantic differences in haplotype frequencies (Árnason, 2004; Árnason & Pálsson, 1996; Árnason et al., 1992, 1998, 2000; Carr & Crutcher, 1998; Carr & Marshall, 1991a,b; Carr et al., 1995; Hardie et al., 2006). …”

“…Trans‐Atlantic differences are evident in protein loci (Jamieson, 1967; Mork, Ryman, Ståhl, Utter, & Sundnes, 1985), mitochondrial cytochrome b (Carr & Marshall, 1991a; Sigurgíslason & Árnason, 2003), and nuclear DNA markers (Pogson, Mesa, & Boutilier, 1995), although results at local scales remain ambiguous. Extensive mtDNA analyses have found little or no structure in waters off the coasts of eastern North America (Carr, Snellen, Howse, & Wroblewski, 1995), Iceland (Árnason, Pálsson, & Arason, 1992; Árnason, Petersen, Kristinsson, Sigurgíslason, & Pálsson, 2000), the Faroe Islands (Sigurgíslason & Árnason, 2003), Norway (Árnason & Pálsson, 1996), and the Baltic Sea (Árnason, Petersen, & Pálsson, 1998). In contrast, microsatellite studies suggest range‐wide isolation by distance (O'Leary, Coughlan, Dillane, McCarthy, & Cross, 2007), and significant structure in waters off North America (e.g., Flemish cap, Bentzen, Taggart, Ruzzante, & Cook, 1996; inshore vs. offshore, Ruzzante, Taggart, Cook, & Goddard, 1996; Arctic populations, Hardie, Gillett, & Hutchings, 2006), Norway (Knutsen, Jorde, André, & Stenseth, 2003), and the North Sea (Hutchinson, Carvalho, & Rogers, 2001).…”

Extent of mitochondrial DNA sequence variation in Atlantic cod from the Faroe Islands: a resolution of gene genealogy

“…On a global scale trans-Atlantic clines are observed in frequencies of common haplotypes (Á rnason, 1998, 2003) and the polymorphism also shows no substructure or net divergence among populations within conventionally divided cod stocks within the various countries. There is, however, some evidence for temporal components to the variation (Á rnason and Pálsson, 1996;.…”

“…The methods used for statistical analysis are as described before (Á rnason and Pálsson, 1996;. The sequence data have been deposited in Genbank under accession numbers AY266685-AY266980.…”

“…A number of studies have been made on population structure and gene flow in Atlantic cod using methods based on variation of mitochondrial DNA (mtDNA, Carr and Marshall, 1991a, b;Á rnason et al, 1992;Pepin and Carr, 1993;Carr et al, 1995;Á rnason and Pálsson, 1996;. In particular, studies using sequence variation of a certain fragment of the mitochondrial cytochrome b (cyt b) gene have revealed a rich polymorphism.…”