Phylogeography and population history of Atlantic mackerel (Scomber scombrusL.): a genealogical approach reveals genetic structuring among the eastern Atlantic stocks

Abstract

Despite the resolving power of DNA markers, pelagic and migratory marine fish species generally show very little geographical population structuring. In mackerel (Scomber scombrus L.) population differentiation has been detected only at a transatlantic scale. By applying two regions in mitochondrial DNA (mtDNA) (D-loop and cytochrome b (cytb)) in combination with genealogical and frequency-based statistical approaches, our data suggest population differentiation among eastern Atlantic spawning stocks. In contrast, and indicative of homing behaviour, no genetic structuring was observed among shoals of individuals outside the spawning season. Among spawning stocks, mtDNA D-loop sequences detected differentiation within the eastern Atlantic, while the cytb gene detected transatlantic differentiation. The impact of recurrent events (e.g. gene flow restricted by isolation by distance) and historic events (e.g. population range expansions) among spawning stocks was investigated applying a nested cladistic analysis of geographical distribution of cytb haplotype lineages. In the eastern Atlantic, historical population range expansion, presumably in connection with recolonization of northern areas after the last glaciation, is suggested to be the main factor determining mtDNA lineage distribution. This was supported by estimates of mtDNA nucleotide diversity, where the highest diversity was observed for the stock spawning in the Bay of Biscay, for which the size estimate is only 15% of the largest stock (Celtic Sea). In addition to revealing population differentiation, our data demonstrate the importance of sampling strategy and the power of applying statistical methods addressing both ongoing and historical population processes.

Mito-nuclear discordance in the degree of population differentiation in a marine goby

“…Microsatellites have proven for many species to be more powerful for resolving population structure than mitochondrial DNA (mtDNA) and allozyme markers (De Innocentiis et al, 2004;Nesb et al, 2000). However, this is not applicable to all marine organisms (Lukoschek et al, 2008).…”

Marked genetic structuring in localised spawning populations of cod Gadus morhua in the North Sea and adjoining waters, as revealed by microsatellites

“…Microsatellites are rapidly mutating, nuclear DNA regions, composed of tandem repeats of short nucleotide motifs of up to 6 nucleotides (Wright 1993). Recent applications of microsatellites have highlighted significant divergence between populations previously thought to be genetically homogenous (Bentzen et al 1996, Ruzzante et al 1996, O'Connell et al 1998, Nesbø et al 2000.…”

“…For example, few previous studies of marine fishes have specifically targeted spawning stocks (Nesbø et al 2000), and yet there is increasing evidence of genetically distinct populations mixing on feeding grounds and subsequently recruiting back to their natal spawning areas (Shaklee et al 1990, Wirgin et al 1997, Ruzzante et al 2000a). Furthermore, sample sizes have often been too small, and the choice of molecular and statistical methods inappropriate (O'Connell & Wright 1997, Ruzzante 1998, Waples 1998.…”

Genetic variation and genetic structure of Caranx hippos (Teleostei: Carangidae) in the Colombian Caribbean

“…Marine fishing resources are often managed under the assumption of panmixia, taking into account that their populations are genetically homogenous due to: i) the absence of geographical barriers, ii) the capacity for dispersion, iii) the tendency to have large population numbers, iv) and the migrations which influence the low level of genetic drift, delaying differentiation amongst populations (Ward, Woodwark, & Skibinski, 1994;Nesbø, Rueness, Iversen, Skagen, & Jakobsen, 2000). Despite all this, evidence of intraspecific differentiation has been found, in which environmental limits and historical phenomena have impeded genetic flow, giving rise to population structuring (Bohonak, 1999;Jolly, Jollivet, Gentil, Thiebaut, & Viard, 2005).…”

“…However, the efficient design of these guidelines depends greatly on the available information regarding the basic levels (that comprise) of biodiversity within a species, such as the genetic diversity, population structure, and interaction with other populations (Gray, 1997;Palumbi, 2003;Kenchington, Heino, & Nielsen, 2003). Therefore, its inclusion in management plans is essential for the identification of conservation entities (Roberts, 1997).Marine fishing resources are often managed under the assumption of panmixia, taking into account that their populations are genetically homogenous due to: i) the absence of geographical barriers, ii) the capacity for dispersion, iii) the tendency to have large population numbers, iv) and the migrations which influence the low level of genetic drift, delaying differentiation amongst populations (Ward, Woodwark, & Skibinski, 1994;Nesbø, Rueness, Iversen, Skagen, & Jakobsen, 2000). Despite all this, evidence of intraspecific differentiation has been found, in which environmental limits and historical phenomena have impeded genetic flow, giving rise to population structuring (Bohonak, 1999;Jolly, Jollivet, Gentil, Thiebaut, & Viard, 2005).…”