Matrilinear phylogeography of Atlantic salmon (Salmo salar L.) in Europe and postglacial colonization of the Baltic Sea area

Abstract

Sixty-four samples from 46 salmon populations totalling 2369 specimens were used for polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the mitochondrial ND1 region. The final analyses included 3095 specimens from 60 populations in Northern Europe. A subsample was analysed by RFLP of ND3/4/5/6. Representative RFLP haplotypes from different parts of the distribution area were sequenced and the phylogeny of European haplotypes and their relations to the North American lineage was described. The four common European haplotypes derive from the ancestral ND1-BBBA (rooting the European clade to the North American) by one-step substitutions: AAAA < AABA < BBBA > BBBB. The Swedish west-coast populations differ from the geographically close southern Baltic, indicating absence of inward and limited outward gene flow through the Danish straits during the last 8000 years. Within the Baltic Sea, only three ND1 haplotypes were detected and there was no variation for ND3/4/5/6. In the whole southern Baltic and in lakes Vänern, Ladoga and Onega the haplotype AABA dominated. Proposed postglacial colonization routes to the Baltic Sea are discussed in relation to the haplotype distribution pattern.

Restricted matrilineal gene flow and regional differentiation among Atlantic salmon (Salmo salar L.) populations within the Bay of Fundy, eastern Canada

“…The network is most parsimoniously linked to the European haplotype group through haplotype i; there are only two main salmon lineages -North American and European (King et al, 2000;Nilsson et al, 2001). Five mutations (0.7% divergence) in the sequenced regions separate the two haplotypes based on the data of Hurst et al (1999;GenBank U12143); six or more mutations separate this European variant from the other haplotypes detected in the present study.…”

“…Only two variable sites were reported for the same part of the gene in 32 salmon derived from a much larger geographical area spanning both Baltic and nonBaltic phylogenetic groups in Europe (Nilsson et al, 2001). Haplotype (h) and nucleotide diversity ( ) observed for Baltic and non-Baltic salmon for the gene region studied were 0.3282 (±0.0768) and 0.000475, and 0.5362 (±0.0904) and 0.000975, respectively (based on data in Nilsson et al, 2001). Average Bay of Fundy values for h and (Table 1) are similar to the more diverse non-Baltic European salmon.…”

“…However, the observation that variation among regions is greater than within regions is surprising as significant regional differentiation has only previously been reported on larger geographical scales. The division of European stocks into Baltic and non-Baltic groups (Koljonen et al, 1999;Nilsson et al, 2001) involves a spatial scale where the Baltic Sea alone, at 422 000 km 2 , is over 20-fold larger than the Bay of Fundy. The regional differentiation observed is predominantly attributed to the difference between populations from the geographically distinct Minas Basin rivers and those elsewhere in the Bay of Fundy.…”

“…The absence of a phylogenetic distinction between the two life-history forms is supported by allozyme studies in both Europe and North America (Ståhl 1987;Verspoor, 1994) though anadromous and non-anadromous populations have diverged sufficiently in some cases to exist sympatrically (Verspoor and Cole, 1989). However, molecular studies do show a deep phylogenetic division between North American and European salmon stocks (Ståhl 1987;Verspoor, 1997;King et al, 2000), and a shallower division of European stocks into Baltic and Atlantic (ie, non-Baltic) groups (Ståhl, 1987;Koljonen et al, 1999;Verspoor et al, 1999;Nilsson et al, 2001). In North America, regional differences have been detected in relation to transferrin variation (Verspoor, 1986) but the evolutionary basis of these regional differences is unclear and detailed phylogeographic studies of North American populations are lacking.…”

The Future of Baltic Sea Populations: Local Extinction or Evolutionary Rescue?

“…In seagrass meadows, it has been shown that stands with less genetic variation are less productive, have lower diversity of associated flora and fauna, and are more susceptible toward extreme climate conditions (Reusch et al 2005). Direct effects on ecosystem services (fisheries harvest) were strongly related to the existence of genetically distinct populations of Sockeye salmon in the Pacific (Schindler et al 2010), and it seems possible that Baltic Sea salmon fishery and possibly other fisheries like the cod fishery may be benefitting in a similar way owing to genetically distinct local stocks (Nilsson et al 2001;Sterner 2007).…”