Population genetic structure and postglacial colonization of Atlantic salmon (Salmo salar) in the Baltic Sea area based on microsatellite DNA variation

Abstract

The genetic structure and phylogeography of Atlantic salmon (Salmo salar) across the Baltic Sea basin and neighbouring areas (eastern Atlantic Ocean, North Sea, Barents Sea, White Sea, and two Russian lakes, Onega and Ladoga) were studied to resolve the partly contradictory hypotheses of the species' postglacial colonization history. Thirty-eight populations (total of 2180 individuals) were studied for nine DNA microsatellite loci. Within the Baltic Sea, the anadromous populations formed three clear groups, corresponding to the northern (Gulf of Bothnia), eastern (Gulf of Finland and eastern Baltic Main Basin), and southern regions (western Baltic Main Basin). The genetic differences among these three groups were clearly greater (G GB 5.6%; G GB being the proportion of diversity components between regions within basins) than were those among population groups in the eastern Atlantic Ocean (G GB 2.2%) from Ireland to the White Sea. The isolation-by-distance model explained part of the differentiation within, but not between, the regions. The results strongly indicate colonization of the Baltic Sea by at least three glacial lineages. Potential refugium areas for each lineage are proposed.Résumé : Nous avons étudié la structure génétique et la phylogéographie du saumon atlantique (Salmo salar) de part en part du bassin de la Baltique et dans les régions avoisinantes (est de l'Atlantique, mer de Barents, mer Blanche et deux lacs russes, les lacs Onega et Ladoga) pour résoudre les hypothèses en partie contradictoires sur l'histoire de la colonisation postglaciaire de l'espèce. Nous avons analysé neuf locus ADN microsatellites chez 2180 individus appartenant à 38 populations. Au sein de la Baltique, les populations anadromes forment trois groupes distincts qui correspondent aux régions du nord (golfe de Bothnie), de l'est (golfe de Finlande et bassin principal de l'est de la Baltique) et du sud (bassin principal de l'ouest de la Baltique). Les différences génétiques entre ces trois groupes sont nettement plus importantes (G GB 5,6 %; G GB représente la proportion d'éléments de diversité entre les régions à l'intérieur des bassins) que celles qui existent entre les groupes de populations de l'est de l'Atlantique (G GB 2,2 %), de l'Irlande à la mer Blanche. Le modèle de l'isolement en fonction de la distance explique une partie de la différentiation au sein des régions, mais non entre elles. Nos résultats indiquent fortement une colonisation de la Baltique par au moins trois lignées glaciaires. Nous proposons des zones possibles de refuge pour chaque lignée.[Traduit par la Rédaction] Säisä et al. 1904

Spawning-Age Differences and their Temporal Trends in Wild and Sea-Ranched Atlantic Salmon Stocks, from Stock Mixture Data

“…The polymerase chain reaction (PCR) and DNA labeling were performed as described in Säisä et al [54]. Microsatellite genotypes were detected with an Applied Biosystems ABI 3130 automated DNA sequencer and analyzed with GENEMAPPER Analysis Software version 4.0, with the size standard of Applied Biosystems GeneScan 500LIZ.…”

Use of multiple markers demonstrates a cryptic western refugium and postglacial colonisation routes of Atlantic salmon (Salmo salar L.) in northwest Europe

“…As proposed for other freshwater fish (Hanfling et al, 2002), it is possible that Atlantic salmon existed north of this refuge, in northwest France or southern England (UKSouth) (Verspoor, 1986), in line with Payne et al's (1971) 'Celtic' hypothesis. In addition, a glacial lake present in the southern North Sea has been proposed as a potential refuge for Atlantic salmon colonising west into the Atlantic and North Sea drainages, east into the Baltic (Verspoor et al, 1999;Säisä et al, 2005) and north into the White and Barents Seas (Verspoor et al, 1999;Asplund et al, 2004;Tonteri et al, 2005), in line with Payne et al's (1971) 'Boreal' hypothesis. However, the allozyme studies of Verspoor (1986), Ståhl (1987) and Bourke et al (1997) have been brought into question by the revelation that a commonly used isoenzyme (ME-2, mMEP-2*) is likely to be acting under selection pressures (Verspoor and Jordan, 1989;Bourke et al, 1997) and as such is not a suitable marker for phylogeographic studies.…”

“…Extensive phylogeographic exploration in the Baltic region and around Russia to the White and Barents Seas has proved successful in elucidating likely glacial refugia for Atlantic salmon in freshwater lakes present in the Baltic region and their subsequent colonisation routes across the region (Nilsson et al, 2001;Asplund et al, 2004;Säisä et al, 2005;Tonteri et al, 2005). In contrast, the phylogeographic history of Atlantic salmon in northwest Europe (northern Spain, France, Britain and Ireland) remains speculative (Verspoor et al, 1999;Nilsson et al, 2001).…”

“…Specifically for Atlantic salmon, the differing yet complementary properties of microsatellite and mitochondrial DNA (mtDNA) have led to robust inferences of phylogeographic histories in the Baltic Seas and northern Europe (Säisä et al, 2005;Tonteri et al, 2005). Our aim, therefore, was to utilise these markers to resolve the phylogeographic history of Atlantic salmon in northwest Europe, by identifying refugial locations and determining colonisation pathways.…”

Climate change and primary industries

“…by groups that may have been isolated for thousands of years in ice-free regions known as glacial refugia. Today, phylogeographic patterns of different salmonids have been linked to colonisation from different glacial refugium (Brunner et al 2001, Säisä et al 2005, McKeown et al 2010, Finnegan et al 2013. Although the phylogeography of salmonids has become clearer in recent years (Crête-Lafrenière et al 2012), further studies are needed to resolve the full history (including mapping the geographical distribution of different lineages) and to characterise biological differences among intraspecific lineages.…”