Mitochondrial DNA diversity in North American and European Atlantic salmon with emphasis on the Downeast rivers of Maine

Abstract

The displacement loop and NADH-1 dehydrogenase regions of mitochondrial DNA (mtDNA) were amplified by the polymerase chain reaction in 954 Atlantic salmon and digested with 40 restriction endonucleases. Variation was detected with 10 enzymes, resulting in 21 composite haplotypes which were strongly patterned geographically with a major discontinuity observed between most North American (NA) and European salmon. Significant heterogeneity of haplotype frequencies was found within and among all classification levels (continent, country, and river). Haplotype frequencies were significantly different across continents, within European samples, within NA samples, within Canadian samples, within wild Maine samples, within captive Maine strains, and between captive and wild Maine strains. Nine haplotypes occurred only in NA, seven in Maine, three only in Maine, and 11 occurred only in Europe. Some Maine rivers had only a single haplotype, suggesting that effective population sizes may be low. The second most frequent European haplotype occurred in tributaries to one Newfoundland river. Gene trees based on parsimony and genetic distance suggest that the haplotypes are monophyletic within each continent, and that the haplotype found on both continents is intermediate between those of Europe and NA, suggesting common ancestry of all haplotypes.

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.…”

“…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 regional differentiation is due largely to >35% of Basin fish being of haplotype ix, a variant not detected elsewhere in the study area (Table 1). Interestingly, clade 1-3 individuals, which include haplotypes ix and x and are detectable by RFLP analysis of the ND1 gene using Alu I, have not been observed elsewhere in North America (Tessier et al, 1997;King et al, 2000;Verspoor, unpublished). Collectively, this strongly supports stocks in the Minas Basin having a unique evolutionary history, at least on the maternal side.…”

Marine Growth and Morphometrics for Three Populations of Atlantic Salmon from Eastern Maine, USA

“…Studies of the genetic structure of these populations relative to neighboring Canadian populations indicate that Maine's Atlantic salmon populations are genetically distinct from the Canadian populations and display statistical differentiation among populations; moreover, these Maine populations exhibit the genetic structure expected in wild populations with similar geographical ranges (King et al 2000;National Research Council 2002). It is unlikely that the remnant populations exist in their pure native form, but their persistence over time in their indigenous habitat suggests that important heritable adaptations probably still exist (Colligan et al 1999).…”

Genetic discrimination for three gynogenetic clones of silver carpHypophthalmichthys molitrix, based on restriction endonuclease analysis of Nd5-Nd6 region of mitochondrial DNA

“…Certain regions of the mtDNA were amplified by polymerase chain reaction (PCR), and their variability and population genetic structure were then analyzed with restriction enzymes (Waldman et al, 1996;King et al, 2000). Isozyme genetic markers as interclonal markers in artificial gynogenetic clones of silver carp were studied (Yang and Gui, 1999).…”