Mitochondrial DNA variation in Pleistocene and modern Atlantic salmon from the Iberian glacial refugium

Abstract

Current understanding of the postglacial colonization of Nearctic and Palearctic species relies heavily on inferences drawn from the phylogeographic analysis of contemporary generic variants. Modern postglacial populations are supposed to be representative of their Pleistocene ancestors, and their current distribution is assumed to reflect the different colonization success and dispersal patterns of refugial lineages. Yet, testing of phylogeographic models against ancestral genomes from glacial refugia has rarely been possible. Here we compare ND1 mitochondrial DNA variation in late Pleistocene (16,000-40,000 years before present), historical and contemporary Atlantic salmon (Salmo salar) populations from northern Spain and other regions of western Europe. Our study demonstrates the presence of Atlantic salmon in the Iberian glacial refugium during the last 40,000 years and points to the Iberian Peninsula as the likely source of the most common haplotype within the Atlantic lineage in Europe. However, our findings also suggest that there may have been significant changes in the genetic structure of the Iberian refugial stock since the last ice age, and question whether modern populations in refugial areas are representative of ice age populations. A common haplotype that persisted in the Iberian Peninsula during the Pleistocene last glacial maximum is now extremely rare or absent from European rivers, highlighting the need for caution when making phylogeographic inferences about the origin and distribution of modern genetic types.

Phylogeography and demographic history of Atherina presbyter (Pisces: Atherinidae) in the North-eastern Atlantic based on mitochondrial DNA

“…In agreement with this climatic history, the majority of the studies found evidence of Pleistocene bottlenecks that were likely caused by periods of strong ocean cooling (e.g. Consuegra et al 2002;Domingues et al 2006Domingues et al , 2007bDomingues et al , 2008Mäkinen and Merilä 2008). However, populations of diVerent species vary in their phylogeographic patterns and we are still far from a comprehensive picture of the evolution of the western European marine icthyofauna during the Pleistocene.…”

“…For the other locations, the spatial expansion model also Wtted the data although the sudden expansion model could not be rejected. The Iberian Peninsula constituted an important glacial refugium for the Atlantic salmon Salmo salar (Consuegra et al 2002). These authors, using ancient salmon DNA, provided evidence suggesting that the present-day genetic make-up of the salmon populations of northern Spain diVers from their constitution during the last glaciation.…”

“…Besides the dispersal capability, the diVerences observed can also be ascribed to factors such as the environmental preferences of a species (which determine what areas can have acted as glacial refugia) (e.g. Consuegra et al 2002;Domingues et al 2008) and the numbers of individuals involved in the process of recolonization of formerly glaciated areas (resulting in the diVerent levels of diversity observed) (e.g. Gysels et al 2004).…”

Refugia of marine fish in the northeast Atlantic during the last glacial maximum: concordant assessment from archaeozoology and palaeotemperature reconstructions

“…The unusual genetic structure in the Baltic Sea may have resulted from population isolation during the complex marine transgression history resulting from the interplay of sea level changes and the isostatic rebound in the early Quaternary (Lepiksaar, 2001, p. 40). However, it has also been used to infer recolonization from possible glacial refugia in the southern North Sea or beyond the eastern edge of the Fennoscandian ice sheet (e.g., Consuegra et al, 2002;Langefors, 2005;King et al, 2007; but see also Makhrov et al, 2005). A westward recolonization pathway into the Baltic Sea from the White Sea after the LGM was previously perceived as unlikely.…”

Contrasting responses to selection in class I and class IIα major histocompatibility-linked markers in salmon

“…Fifth, the Atlantic salmon is one of the few species where MH polymorphism has been experimentally shown to be associated with resistance/susceptibility to specific pathogens (Grimholt et al, 2003). Furthermore, historical samples are widely available from Atlantic salmon populations, often as dried scales that are suitable for extraction of DNA, allowing analysis of temporal variation within populations (Nielsen et al, 1999;Consuegra et al, 2002;Ciborowski et al, 2007).…”