Protein polymorphism in Atlantic salmon within a Scottish river: evidence for selection and estimates of gene flow between tributaries

Verspoor, Eric; Fraser, Neil H. C.; Youngson, A. F.

doi:10.1016/0044-8486(91)90385-k

Cited by 62 publications

(67 citation statements)

References 16 publications

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“…We found an overall deficiency of heterozygotes, which probably can be ascribed to population substructure within river systems, as previously reported for the same species (Verspoor et al 1991;Tessier et al 1997). Alternatively, it could be explained by the presence of null alleles.…”

Section: Discussionsupporting

confidence: 58%

“…The genetic differentiation found among populations from different geographical regions (Denmark, Sweden, and Scotland), was in the range of what has been reported from other studies of Atlantic salmon (Stahl 1981;Elo 1993;Nielsen et al 1996) among populations on the Danish west coast, however, was generally smaller, and in one instance (between the Skjern and Storaaen Rivers) in the range of what has been reported among tributaries within the same river system (Verspoor et al 1991). The high level of gene flow between these rivers could be explained by a reduced precision in homing among salmon from the Danish west coast, but could also be a consequence of the apparently similar environmental conditions among these rivers (such as depth, water velocity, temperature, etc.).…”

Section: Discussionmentioning

confidence: 48%

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Genetic Variation in Time and Space: Microsatellite Analysis of Extinct and Extant Populations of Atlantic Salmon

Hansen²,

1999

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Abstract.-Information on genetic composition of past and present populations may be obtained by analyzing DNA from archival samples. A study is presented on the genetic population structure of extant and extinct local populations of Atlantic salmon from 1913 to 1989 using dried scales as a source of DNA. Variation at six micro satellite loci was studied. Tests for differentiation among populations and among time series within populations showed that population structure was stable over time. This was also confirmed by a neighbor-joining dendrogram, which showed a clear clustering of samples from individual rivers that covered a time span of up to 76 years. These results suggest that salmon populations evolve as semi-independent units connected by modest amounts of gene flow. Additionally, a clear association between geographic and genetic distance was found. This relationship has otherwise been difficult to establish in several recent studies. The discrepancy may be due to impact of human activities on the genetic structure of present populations, whereas old samples represent populations in a more unaffected state. However, other explanations related to differences in the sampling of past and present populations may be equally valid.

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Section: Discussionsupporting

confidence: 58%

Section: Discussionmentioning

confidence: 48%

Genetic Variation in Time and Space: Microsatellite Analysis of Extinct and Extant Populations of Atlantic Salmon

Hansen²,

1999

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“…However, this did not appear to be the case within the River Tweed system. The low level of genetic differentiation found in the River Tweed system appears to be exceptional, as significant genetic heterogeneity has been found within a number of other large river systems in Scotland and elsewhere (Stihl 1987;Verspoor et al 1991).…”

Section: Discussionmentioning

confidence: 96%

Genetic Protein Variation in Natural Populations of Atlantic Salmon (Salmo salar) in Scotland: Temporal and Spatial Variation

Jordan¹,

Youngson²,

Hay³

et al. 1992

Can. J. Fish. Aquat. Sci.

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1992. Genetic protein variation in natural populations of Atlantic salmon (Salmo salar) in Scotland: temporal and spatial variation. Can. J. Fish. Aquat. Sci. 49: 1863-1 872.Levels of temporal and spatial genetic heterogeneity within and among Atlantic salmon (Salmo salar) populations in Scotland were assessed through starch-gel electrophoretic analysis of variation at 30 protein-coding loci. Over three year-classes the level of temporal variation within populations was generally nonsignificant, although significant heterogeneity among year-classes was found at some loci at some locations. Hierarchical analysis of gene diversity showed that 97.6% of the genetic diversity was found within single sites, with the remaining diversity distributed among sites. While there was no evidence of subpopulation differentiation among a number of samples of Atlantic salmon from the River Tweed system, significant genetic heterogeneity was observed among samples from different river systems within Scotland. Comparison of the levels of among-population heterogeneity in the Atlantic salmon with those found in the closely related brown trout (Salmo trutta) over a similar geographical area shows the Atlantic salmon to be relatively genetically homogeneous.Nous avons mesure I'het6rogkn6it6 gknetique temporelle et spatiale entre populations et a I'interieur de populations de saumons de I'Atlantique (Salmo salar) d'Ecosse grace a une analyse par 6lectrophorese sur gel d'amidon de la variation a 30 loci qui codent les proteines. Sur trois classes annuelles, la variation temporelle a I'interieur des populations n'etait generalement pas significative, mais on a trouv6 une hi.ti.rogi.neit6 significative entre les classes annuelles pour certains loci sur des sites donnes. L'analyse hierarchique de la diversite genktique a montr6 que 97,6 % de cette diversit6 se retrouvait sur des sites pris individuellement, le reste etant distribuk entre les sites. S'il n'y avait aucune indication de differenciation entre des sous-populations parmi un certain nombre d'6chantillons de saumons de I'Atlantique du reseau de la Tweed, on a observe un? hGtkrogenkit6 genetique significative entre des echantillons provenant de differents bassins hydrographiques d'Ecosse. La comparaison de I'het6rogeneit6 parmi les populations de saumons de I'Atlantique avec les resultats obtenus chez I'espece proche que constitue la truite brune (Salmo trutta) dans une zone gkographique similaire montre que le saumon de I'Atlantique presente une relative hetkrogkneite gknktique.T he susceptibility of a fish species to loss of genetic diversity through exploitation or abuse by man depends on the manner in which genetic variation is distributed within and among populations of the species concerned (Ryman 1983). Depletion of genetic variability can have effects at many levels: it may affect the fitness of individuals, reduce the potential of populations for adaptation to changing environments, and ultimately alter the pace of longer term evolutionary processes such 'Author to whom co...

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“…We found a longitudinal east-west cline of MEP-2*100 frequencies which could be associated with a cline of summer freshwater temperatures (higher water temperature, higher frequency of the *100 allele). Although the range of our river temperatures was much less than the cline of temperatures considered by Verspoor and Jordan (1989) and Verspoor et al (1991) who included rivers from Iceland to Spain, there may be differences in genotype because of temperature. Nicieza et al (1994) found that individuals belonging to a stock with a frequency of MEP-2*100 of 0.311 had higher digestive performance than individuals from another stock with a frequency of 0.852.…”

Section: Discussionmentioning

confidence: 99%

“…The electrophoretic variants of the locus MEP-2* (100, 125), that determine the malic enzyme expressed in the mitochondrial fraction of heart and skeletal muscle, have been related to the age of returning adults, the frequency of heterozygotes being generally higher in grilse than in salmon (Jordan et al, 1990). MEP-2* allele frequencies in both American and European populations have also been correlated with freshwater summer temperatures, suggesting that the polymorphism at that locus may be maintained by selective pressures (Verspoor and Jordan, 1989;Verspoor et al, 1991). High frequencies of the *100 allele in juveniles are associated with high summer temperatures in the river, producing a latitudinal cline in European and American river systems, in which MEP-2*100 frequency increases north-south.…”

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confidence: 98%

The malic enzyme MEP-2* locus in Spanish populations of Atlantic salmon: Sea age and foreign stocking

1998

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Wild Spanish populations of Salmo salar were analyzed for their variability at the MEP-2* locus that determines the malic enzyme expressed in muscle mitochondria. The allele frequencies of these populations have been found to be associated with sea-age of returning adults and freshwater temperature; in a minor extent with foreign stocking of Irish and Scottish alevins; and finally, no association was found with precocious parr maturation.Natural populations are often assumed to be in equilibrium; nevertheless, HardyWeinberg conditions are rarely reached in any population. Genetic equilibrium is maintained by a delicate balance between several forces such as selection, genetic drift and gene flow that can promote major changes of the genetic composition (gene and genotype frequencies) of populations. These factors are critical in small or declining populations, in which a little change could result in extinction.A case of a species with populations bordering extinction is the Atlantic salmon (Salmo salar L.) in many Spanish rivers, such as the Asturian ones, located in the central area of Northern Spain (Figure 1). The headwaters of these rivers are placed in a cline of heights following the Cantabric mountain chain, decreasing from East to West, a fact that displays a longitudinal cline of water temperatures (mean summer temperature ranging from 12.6 ºC in the Cares to 16.4 ºC in the Esva in 1990; data from official routine records of the Confederacion Hidrografica del Norte). The stocks of these rivers typically consist of a majority of two-sea-winter salmon with variable proportions of one-sea-winter grilse (Nicieza and Braña, 1993). Placed on the southern limit of the European distribution of this species, the sizes of Spanish populations have decreased dramatically during this century, having been reduced to a few adults in many cases. The reduction of population sizes is

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Protein polymorphism in Atlantic salmon within a Scottish river: evidence for selection and estimates of gene flow between tributaries

Cited by 62 publications

References 16 publications

Genetic Variation in Time and Space: Microsatellite Analysis of Extinct and Extant Populations of Atlantic Salmon

Genetic Variation in Time and Space: Microsatellite Analysis of Extinct and Extant Populations of Atlantic Salmon

Genetic Protein Variation in Natural Populations of Atlantic Salmon (Salmo salar) in Scotland: Temporal and Spatial Variation

The malic enzyme MEP-2* locus in Spanish populations of Atlantic salmon: Sea age and foreign stocking

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