Paul Bentzen
Dalhousie University, Biology, Faculty Member
We report the development of a semiautomated multilocus genotyping system for Pacific salmon using four-color fluorescent detection of microsatellites. An initial screening of microsatellites was conducted on five species of Pacific... more
We report the development of a semiautomated multilocus genotyping system for Pacific salmon using four-color fluorescent detection of microsatellites. An initial screening of microsatellites was conducted on five species of Pacific salmon (Oncorhynchus spp.) and Atlantic salmon (Salmo salar) using 35 primer pairs developed from six species of salmonid. The number of loci that amplified varied by species from 11 (chum salmon) to 22 (chinook salmon). We then tested co-amplification of microsatellites in chinook, coho, and sockeye salmon and developed six-locus multiplex systems. The species-specific multiplex systems were applied to two populations using a sequencer/gene scanner (Perkin-Elmer Applied Biosystems, Inc. [ABI] 373A). The genetic variability at each locus was calculated to evaluate the utility of this system for genetic studies. Significant differences in allele frequencies were observed between populations in 14 of 18 pair-wise comparisons. Average heterozygosity ranged ...
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Clinal variation across replicated environmental gradients can reveal evidence of local adaptation, providing insight into the demographic and evolutionary processes that shape intraspecific diversity. Using 1773 genome-wide single... more
Clinal variation across replicated environmental gradients can reveal evidence of local adaptation, providing insight into the demographic and evolutionary processes that shape intraspecific diversity. Using 1773 genome-wide single nucleotide polymorphisms we evaluated latitudinal variation in allele frequency for 134 populations of North American and European Atlantic salmon (). We detected 84 (4.74%) and 195 (11%) loci showing clinal patterns in North America and Europe, respectively, with 12 clinal loci in common between continents. Clinal single nucleotide polymorphisms were evenly distributed across the salmon genome and logistic regression revealed significant associations with latitude and seasonal temperatures, particularly average spring temperature in both continents. Loci displaying parallel clines were associated with several metabolic and immune functions, suggesting a potential basis for climate-associated adaptive differentiation. These climate-based clines collective...
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Individual assignment and genetic mixture analysis are commonly utilized in contemporary wildlife and fisheries management. Although microsatellite loci provide unparalleled numbers of alleles per locus, their use in assignment... more
Individual assignment and genetic mixture analysis are commonly utilized in contemporary wildlife and fisheries management. Although microsatellite loci provide unparalleled numbers of alleles per locus, their use in assignment applications is increasingly limited. However, next-generation sequencing, in conjunction with novel bioinformatic tools, allows large numbers of microsatellite loci to be simultaneously genotyped, presenting new opportunities for individual assignment and genetic mixture analysis. Here, we scanned the published Atlantic salmon genome to identify 706 microsatellite loci, from which we developed a final panel of 101 microsatellites distributed across the genome (average 3.4 loci per chromosome). Using samples from 35 Atlantic salmon populations ( = 1,485 individuals) from coastal Labrador, Canada, a region characterized by low levels of differentiation in this species, this panel identified 844 alleles (average of 8.4 alleles per locus). Simulation-based evalu...
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Adaptive radiation involving a colonizing phenotype that rapidly evolves into at least one other ecological variant, or ecotype, has been observed in a variety of freshwater fishes in post-glacial environments. However, few studies... more
Adaptive radiation involving a colonizing phenotype that rapidly evolves into at least one other ecological variant, or ecotype, has been observed in a variety of freshwater fishes in post-glacial environments. However, few studies consider how phenotypic traits vary with regard to neutral genetic partitioning along ecological gradients. Here, we present the first detailed investigation of lake trout Salvelinus namaycush that considers variation as a cline rather than discriminatory among ecotypes. Genetic and phenotypic traits organized along common ecological gradients of water depth and geographic distance provide important insights into diversification processes in a lake with high levels of human disturbance from over-fishing. Four putative lake trout ecotypes could not be distinguished using population genetic methods, despite morphological differences. Neutral genetic partitioning in lake trout was stronger along a gradient of water depth, than by locality or ecotype. Contemp...
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Research Interests: Genetics, Genetic Drift, Biotechnology, Biology, Genetic Diversity, and 15 morePopulation, Microsatellites, Genetic Population Structure, Microsatellite, DNA markers, Fisheries Sciences, Pacific Salmon, Genetic Differentiation, Local adaptation, Genetic Markers, Allele Frequency, Cumulant, log likelihood ratio, alleles, and progeny
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Research Interests: Genetics, Geography, Gene Flow, Mass Spectrometry, Biology, and 15 moreMedicine, Biological Sciences, Discriminant Analysis, Animals, Fishes, Animal migration, Cluster Analysis, Laser Ablation, Discriminant function analysis, Genetic Differentiation, Genotype, Marine Environment, First Year, Early Life History, and Elemental composition
Research Interests: Paleontology, Population Genetics, Biology, Population Dynamics, Medicine, and 15 moreGenetic Diversity, Molecular Ecology, Biological Sciences, Molecular, Commerce, Mitochondrial DNA, Hair, Microsatellites, Animals, Ancient DNA, Inbreeding Depression, Captive Wild Animals, Otters, Genetic variation, and Bone and Bones
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Diversification of freshwater fishes on islands is considered unlikely because the traits that enable successful colonization-specifically, broad salinity tolerances and the potential for oceanic dispersal-may also constrain... more
Diversification of freshwater fishes on islands is considered unlikely because the traits that enable successful colonization-specifically, broad salinity tolerances and the potential for oceanic dispersal-may also constrain post-colonization genetic differentiation. Some secondary freshwater fish, however, exhibit pronounced genetic differentiation and geographic structure on islands, whereas others do not. It is unclear what conditions give rise to contrasting patterns of differentiation because few comparative reconstructions of population history have been carried out for insular freshwater fishes. In this study, we examined the phylogeography of Hart's killifish (Rivulus hartii) across Trinidad, with reference to neighboring islands and northern South America, to test hypotheses of colonization and differentiation derived from comparable work on co-occurring guppies (Poecilia reticulata). Geographic patterns of mitochondrial DNA haplotype variation and microsatellite genot...
Research Interests: Phylogeography, Biology, Population Dynamics, Biogeography, Island Biogeography, and 15 moreMedicine, Molecular Ecology, Biological Sciences, Colonization, Molecular, Mitochondrial DNA, Haplotypes, Animals, Trinidad and Tobago, Cyprinodontiformes, Poecilia, Rivulus, Fresh water, Genetic variation, and West Indies
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Samples of walleye pollock (Theragra chalcogramma) from the North Pacific Ocean and Bering Sea were screened for variation at the pantophysin (PanI) locus. Global genetic differentiation across samples (FST = 0.038) was considerably... more
Samples of walleye pollock (Theragra chalcogramma) from the North Pacific Ocean and Bering Sea were screened for variation at the pantophysin (PanI) locus. Global genetic differentiation across samples (FST = 0.038) was considerably greater than reported in previous population studies using allozymes, mtDNA, or microsatellite loci and significantly greater than FSTdistributions of neutral loci simulated over a large range of locus heterozygosity. PanI allele frequencies varied over a broad latitudinal gradient and were correlated with estimated mean surface temperatures, resulting in the greatest levels of genetic divergence between the northern Bering Sea and the southernmost locations in the temperate Pacific Ocean (Puget Sound, Japan). The discordance between estimates of population differentiation estimated from PanI and other neutral marker classes, both in magnitude and in geographic patterns, could arise from temperature-mediated effects of natural selection over broad geogra...
Research Interests: Zoology, Biology, Ecology, Natural Selection, Canadian, and 14 morePuget Sound, Land Surface Temperature, Fisheries Sciences, Marine Fish, Latitudinal Gradient, Genetic Differentiation, Genetic Divergence, Pacific ocean, Population Study, North Pacific Ocean, Walleye pollock, Stock Identification, surface temperature, and microsatellite loci
We used multilocus microsatellite analysis to compare the reproductive success of naturally spawning wild steelhead trout (Oncorhynchus mykiss) with a newly established sympatric hatchery population in Forks Creek, Washington, U.S.A.... more
We used multilocus microsatellite analysis to compare the reproductive success of naturally spawning wild steelhead trout (Oncorhynchus mykiss) with a newly established sympatric hatchery population in Forks Creek, Washington, U.S.A. Hatchery steelhead spawning in the wild had markedly lower reproductive success than native wild steelhead. Wild females that spawned in 1996 produced 9 times as many adult offspring per capita as did hatchery females that spawned in the wild. Wild females that spawned in 1997 produced 42 times as many adult offspring as hatchery females. The wild steelhead population more than met replacement requirements (approximately 3.76.7 adult offspring were produced per female), but the hatchery steelhead were far below replacement requirements (<0.5 adults per female). The survival differential was greatest in the freshwater environment (i.e., production of seaward-migrating juveniles), but survival at sea favored the hatchery population in 1 year and the w...
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We evaluated the spatial scale of metapopulation structure and genetic connectivity in rainbow smelt, Osmerus mordax, using eight microsatellite loci at 22 spawning locations throughout Newfoundland and Labrador. Consistent with low gene... more
We evaluated the spatial scale of metapopulation structure and genetic connectivity in rainbow smelt, Osmerus mordax, using eight microsatellite loci at 22 spawning locations throughout Newfoundland and Labrador. Consistent with low gene flow and limited dispersal, significant genetic structuring (FST ≈ 0.11) was present at small spatial scales (<200 km). Moreover, strong isolation by distance (IBD, P < 0.001, r2 = 0.47) was observed, which was linear at small scales and nonlinear at large distances (>200 km). We hypothesized that despite high dispersal potential associated with a pelagic larval stage, behaviours restricting gene flow may result in structuring at the estuary scale. Multidimensional scaling and neighbour-joining of multilocus genotypes indicate some bay-scale associations. However, a comparison of FST values and IBD residuals at both estuary and bay scales indicated low structure within and elevated structure among estuaries. Estuarine structuring was furthe...
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Species long-term persistence is contingent on the ability of populations to mount variable responses to perturbations; the breadths of which are largely dependent on amounts of heritable variation present at the population level.... more
Species long-term persistence is contingent on the ability of populations to mount variable responses to perturbations; the breadths of which are largely dependent on amounts of heritable variation present at the population level. However, populations are not necessarily equivalent in their amounts of genetic variation, or in responses to future environmental conditions, and information about the magnitude and spatial distribution of intraspecific genetic variation is integral to conservation planning, and preserving species evolutionary potential. Using neutral molecular markers, I examined the magnitude and spatial distribution of microsatellite based variation for 33 populations of American shad (Alosa sapidissima) from across the species’ range. Sequential reductions of genetic variation with latitude were observed among populations from formerly glaciated regions; consistent with stepwise post-glacial range expansion, and successive population founder events. Different spatial ...
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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... more
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 ...
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Research Interests: Paleontology, Population Genetics, Population Dynamics, Genetic Diversity, Molecular Ecology, and 13 moreBiological Sciences, Molecular, Commerce, Mitochondrial DNA, Hair, Microsatellites, Animals, Ancient DNA, Inbreeding Depression, Captive Wild Animals, Otters, Genetic variation, and Bone and Bones
American Shad Alosa sapidissima in the Hudson River, New York, and coastwide have shown major long-term declines. A possible contributing factor is commercial fisheries that harvest this population outside of the Hudson River estuary.... more
American Shad Alosa sapidissima in the Hudson River, New York, and coastwide have shown major long-term
declines. A possible contributing factor is commercial fisheries that harvest this population outside of the Hudson
River estuary. Using previously published and new reference microsatellite data from 33 baseline populations, our
goals were (1) to estimate the proportion of Hudson River American Shad contributing to the two remaining major
mixed-stock fisheries along the Atlantic coast in Delaware Bay and the Bay of Fundy and (2) to estimate the
proportions of other American Shad stocks contributing to these two fisheries at the highest level of stock
specificity. Stock composition estimates for 2009 and 2010 Delaware Bay collections were made using three models
that ranged from the most simple question (Hudson River and Delaware Bay populations) to one with all 33
baseline populations included. In all cases, a Hudson River contribution nearly equal to that of the Delaware Bay
contribution was observed, indicating a substantial take on the otherwise protected Hudson River population.
When all baseline populations were included for the larger 2010 Delaware Bay collection, 19 showed nonzero
contributions, largely drawn from mid-Atlantic U.S. rivers. The 2009 Bay of Fundy collection showed
contributions from across most of the species’ range but was dominated by northern populations. Mixed-stock
analyses of collections from the two sites together indicate that these estuarine fisheries harvested not only proximal
populations but those originating from a wide latitudinal range.
declines. A possible contributing factor is commercial fisheries that harvest this population outside of the Hudson
River estuary. Using previously published and new reference microsatellite data from 33 baseline populations, our
goals were (1) to estimate the proportion of Hudson River American Shad contributing to the two remaining major
mixed-stock fisheries along the Atlantic coast in Delaware Bay and the Bay of Fundy and (2) to estimate the
proportions of other American Shad stocks contributing to these two fisheries at the highest level of stock
specificity. Stock composition estimates for 2009 and 2010 Delaware Bay collections were made using three models
that ranged from the most simple question (Hudson River and Delaware Bay populations) to one with all 33
baseline populations included. In all cases, a Hudson River contribution nearly equal to that of the Delaware Bay
contribution was observed, indicating a substantial take on the otherwise protected Hudson River population.
When all baseline populations were included for the larger 2010 Delaware Bay collection, 19 showed nonzero
contributions, largely drawn from mid-Atlantic U.S. rivers. The 2009 Bay of Fundy collection showed
contributions from across most of the species’ range but was dominated by northern populations. Mixed-stock
analyses of collections from the two sites together indicate that these estuarine fisheries harvested not only proximal
populations but those originating from a wide latitudinal range.