Lack of divergence in the mitochondrial cytochromebgene betweenMacruronusspecies (Pisces: Merlucciidae) in the Southern Hemisphere

Abstract

Two species of grenadier, the blue grenadier (or hoki) Macruronus novaezelandiae and the Patagonian grenadier M. magellanicus, have been recorded in the Southern Hemisphere with disjunct distributions along southern Australia-New Zealand and southern Chile-Argentina, respectively. The extent of genetic difference between these two putative species was examined using partial sequences (n = 44; 405 bp) of the mitochondrial DNA cytochrome b gene in a phylogenetic analysis and in an analysis of molecular variance (AMOVA). Our analysis showed a lack of genetic differentiation between species (F ST = -0.02275, Φ ST = -0.00250) and among stocks. This absence of genetic differences is consistent with recent larval and adult morphology data suggesting that the two species should be synonymised. A comparable lack of genetic isolation has been observed in other closely related taxa (genera Merluccius and Micromesistius) with similar disjunct distributions across the Southern Hemisphere.

Low genetic differentiation between two geographically separated populations of demersal gadiform fishes in the Southern Hemisphere

“…The previous results from sequence analyses of protein-coding genes for the two species of grenadier also showed a lack of genetic differentiation between species (Olavarría et al, 2006;Ward, 2009). These results challenge the idea that the two pairs of the closely related gadiform fishes represent two distinct species and subspecies, respectively.…”

The taxonomic status of the South African straptail, Macruronus capensis Davies, 1950 (Pisces, Gadiformes, Macruronidae)

“…However, they retained M. capensis because they were unable to examine material of this species. The molecular study of Olavarría et al (2006) confirmed the synonymy of M. magellanicus and M. novaezlandiae. These authors also excluded M. capensis from their analysis, accepting its validity with the caveat that the nature of the studies by Inada (1990) and Lloris et al (2003) precluded a reevaluation of their decisions.…”

“…Olavarría et al's (2006) molecular study, using cytochrome b data from the same fragment, argued for the status of M. magellanicus as a junior synonym of M. novaezelandiae, based on the lack of differentiation among the two populations; a shared haplotype was the most abundant in both species, and low levels of population differentiation were only due to rare haplotypes within each. In the present case, the M. capensis cytochrome b haplotype is identical to this shared, common haplotype in M. magellanicus (Olavarría et al 2006) and M. novaezelandiae (Baker et al 1995;Olavarría et al 2006). While the analysis of a single specimen precludes a more detailed consideration of population differentiation, the comparison of this sequence to other sequences from M. magellanicus reveals this divergence to be no more extensive than divergences among the M. magellanicus sequences themselves.…”

“…The PCR was set up in a 25 µL volume, following the protocol, concentrations and thermocycling regime of Ward et al (2005). A fragment of the cytochrome b gene was also amplified, using the primers tGludg (Gludg-L) and CB3-H (Palumbi et al 2007), and the PCR conditions of Olavarría et al (2006). Successful amplification was determined as in Uiblein & Gouws (2014).…”

“…The COI fragment was subjected to an identification query within BOLD (Barcode of Life Data Systems; Ratnasingham & Hebert 2007). The cytochrome b sequence was aligned [using ClustalX2 (Larkin et al 2007)] with and compared to the three unique haplotypes (downloaded from GenBank) present among 17 individuals of Macruronus magellanicus (the junior synonym of M. novaezelandiae) collected from southern Chile and published by Olavarría et al (2006). Of these three haplotypes, two were found in single individuals, but the most common haplotype (Mno-A) was also the most common haplotype found in M. novaezelandiae from three fishing grounds off New Zealand and a locality west of Tasmania in an earlier study (Baker et al 1995), occurring in 23 of 27 sampled individuals.…”