Mitochondrial DNA Polymorphism, Population Structure, and Life History Variation in American Shad (Alosa sapidissima)

1989 ◽  
Vol 46 (8) ◽  
pp. 1446-1454 ◽  
Author(s):  
Paul Bentzen ◽  
Gregory C. Brown ◽  
William C. Leggett
Keyword(s):  
Mitochondrial Dna ◽  
Population Structure ◽  
Reproductive Traits ◽  
Restriction Endonuclease Analysis ◽  
American Shad ◽  
Life History Variation ◽  
Alosa Sapidissima ◽  
Mitochondrial Dna Polymorphism ◽  
Mtdna Variation ◽  
Mtdna Sequence

Restriction endonuclease analysis of mitochondrial DNA (mtDNA) variation was used to assess genetic differentiation and population structure in American shad (Alosa sapidissima) sampled from 14 rivers spanning the native range of the species (Florida to Quebec). Estimated mtDNA sequence divergences among 52 shad surveyed with 16 endonucleases were relatively low (mean 0.2%). The low level of mtDNA variation in shad may be a consequence of population bottlenecks that occurred during Pleistocene glacial maxima. A survey of 243 shad with four enzymes revealed several genotypes that were distributed across the range of the species. Three genotypes, a length variant and two single-enzyme genotypes, exhibited nonrandom, geographically clumped distributions. The distributions of shad mtDNA genotypes may have been influenced primarily by founder effects in the northern (glaciated) part of the range, and gene flow in the southern part of the range. The mtDNA data suggest that differences in the reproductive traits of northern and southern populations of shad, if genetically mediated, are likely to have evolved since the Pleistocene. The results of this study support theoretical predictions that mtDNA analysis is a highly sensitive means of examining population structures.

Discrimination among Atlantic Coast Populations of American Shad (Alosa sapidissima) Using Mitochondrial DNA

1991 ◽  
Vol 48 (9) ◽  
pp. 1724-1734 ◽  
Author(s):  
Kathleen Nolan ◽  
Joseph Grossfield ◽  
Isaac Wirgin
Keyword(s):  
Mitochondrial Dna ◽  
Atlantic Coast ◽  
Restriction Enzymes ◽  
Hudson River ◽  
Restriction Endonuclease Analysis ◽  
The United States ◽  
American Shad ◽  
Alosa Sapidissima ◽  
Coastal Fisheries ◽  
Latitudinal Clines

We used restriction endonuclease analysis of mitochondrial DNA (mtDNA) to differentiate among spawning stocks of American shad (Alosa sapidissima). Highly purified mtDNA was isolated from shad from four major spawning rivers: the St. John's (Florida), the Delaware, and the Hudson in the United States and the Miramichi in New Brunswick, Canada. Primarily four-and-five-base-cutting restriction enzymes were used to prepare both individual enzyme profiles and composite genotypes. Three separate spawning stocks, St. John's, Delaware–Hudson, and Miramichi, could be distinguished based on frequency differences in mtDNA genotypes generated by single restriction enzyme digests. We could not distinguish Delaware from Hudson River shad. Only a single definitive restriction site polymorphism was observed among all samples, but polyacrylamide gel electrophoretic mobility variants were common. Eco RI, Dde I, and Rsa I revealed stock-specific mtDNA genotypes. The frequencies of some genotypes occurred in latitudinal clines. Fifty-seven of 81 fish showed individual-specific composite genotypes. Geographic partitioning of genotypes suggests that mtDNA analysis may be useful for the identification of some American shad stocks and their relative contributions to mixed coastal fisheries.

scholarly journals Length and restriction site heteroplasmy in the mitochondrial DNA of american shad (alosa sapidissima).

Genetics ◽  
1988 ◽  
Vol 118 (3) ◽  
pp. 509-518
Author(s):  
P Bentzen ◽  
W C Leggett ◽  
G G Brown
Keyword(s):  
Mitochondrial Dna ◽  
South Carolina ◽  
Nova Scotia ◽  
Length Polymorphism ◽  
Restriction Site ◽  
Restriction Endonuclease Analysis ◽  
American Shad ◽  
Length Variation ◽  
Alosa Sapidissima ◽  
Size Classes

Abstract Restriction endonuclease analysis was used to assess mitochondrial DNA (mtDNA) variation in American shad (Alosa sapidissima) collected from 14 rivers ranging from Florida to Quebec. Two types of heteroplasmy were observed, one involving a major length polymorphism and the other a single restriction site. Shad mtDNA occurred in two principal size classes, 18.3 and 19.8 kb. Of 244 shad examined, 30 were heteroplasmic and carried both size classes of mtDNA in varying proportions; the remainder were homoplasmic for the smaller size class of mtDNA. The large mtDNA variant occurred most frequently at the southern end of the range, and except for two individuals from Nova Scotia, was not detected among shad from rivers north of the Delaware. In contrast, ten shad heteroplasmic for a SalI restriction site originated from rivers ranging from South Carolina to Nova Scotia. DNA mapping and hybridization experiments indicated that the length polymorphism is in the D-loop-containing region and consists of a tandemly repeated 1.5-kb DNA sequence occurring in two and three copies, respectively, in the two major size classes of shad mtDNA. Continuous length variation up to approximately 40 bp occurs among copies of the repeat both within and among individuals. Restriction site data support the conclusion that both forms of heteroplasmy in shad mtDNA have originated more than once.

Taking stock: defining populations of American shad (Alosa sapidissima) in Canada using neutral genetic markers

2010 ◽  
Vol 67 (6) ◽  
pp. 1021-1039 ◽  
Author(s):  
Daniel J. Hasselman ◽  
Rod G. Bradford ◽  
Paul Bentzen
Keyword(s):  
Population Structure ◽  
Genetic Variation ◽  
Isolation By Distance ◽  
Analysis Of Covariance ◽  
American Shad ◽  
Migration Route ◽  
Conservation Units ◽  
Geographic Scale ◽  
Alosa Sapidissima ◽  
Conservation Concern

Knowledge of the scale of population structure is a prerequisite for designating conservation units. American shad ( Alosa sapidissima ) are of increasing conservation concern, but the scale of population structure within the Canadian portion of the species range is unknown. Using 13 microsatellite loci, we examined the partitioning of genetic variation within four and among 12 Canadian drainages. We detected significant (p < 0.05) and temporally stable genetic differentiation among all drainages, supporting the hypothesis that rivers support genetically distinct populations. However, Bayesian methods identified seven clusters and provided evidence for shad metapopulation structure. We observed a significant (p < 0.01) pattern of isolation by distance (IBD) among all drainages. A strong linear IBD (r = 0.98) was observed among rivers that were outside the Bay of Fundy (BoF). A hypothesized counterclockwise migration route explained a greater proportion of genetic variation (r = 0.87) among BoF rivers than direct route based distances (r = 0.14). Although IBD patterns did not differ regionally (analysis of covariance; p > 0.05), the degree of differentiation among BoF rivers was greater than that among non-BoF rivers, regardless of the geographic scale of comparison. Our results suggest that fisheries managers need to be concerned with the loss of shad genetic diversity on both river and regional scales.

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