Analysis of mtDNA indicates weak temporal genetic heterogeneity in pink salmon spawning runs in two rivers on Sakhalin Island

Брыков, Вл. А.; Polyakova, N. E.; Скурихина, Л. А.; Kukhlevsky, A. D.; Kirillova, O. N.; Churikov, D.; Pudovkin, Alexander I.; Gharrett, Anthony J.

doi:10.1111/j.1095-8649.1999.tb00703.x

Cited by 18 publications

(11 citation statements)

References 28 publications

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“…No studies of IBT have yet employed the pairwise approach so often used for IBD, although some studies had the opportunity to do so. For example, Brykov et al (1999) collected pink salmon (Oncorhynchus gorbuscha) at four different times in each of two rivers. They found significant mtDNA differences associated with breeding time, but did not analyse their data in a pairwise fashion.…”

Section: Empirical Evidencementioning

confidence: 99%

Population structure attributable to reproductive time: isolation by time and adaptation by time

2005

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Many populations are composed of a mixture of individuals that reproduce at different times, and these times are often heritable. Under these conditions, gene flow should be limited between early and late reproducers, even within populations having a unimodal temporal distribution of reproductive activity. This temporal restriction on gene flow might be called 'isolation by time' (IBT) to acknowledge its analogy with isolation by distance (IBD). IBD and IBT are not exactly equivalent, however, owing to differences between dispersal in space and dispersal in time. We review empirical studies of natural populations that provide evidence for IBT based on heritabilities of reproductive time and on molecular genetic differences associated with reproductive time. When IBT is present, variation in selection through the reproductive season may lead to adaptive temporal variation in phenotypic traits [adaptation by time (ABT)]. We introduce a novel theoretical model that shows how ABT increases as (i) selection on the trait increases; (ii) environmental influences on reproductive time decrease; (iii) the heritability of reproductive time increases; and (iv) the temporal distribution of reproductive activity becomes increasingly uniform. We then review empirical studies of natural populations that provide evidence for ABT by documenting adaptive temporal clines in phenotypic traits. The best evidence for IBT and ABT currently comes from salmonid fishes and flowering plants, but we expect that future work will show these processes are more widespread.

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Section: Empirical Evidencementioning

confidence: 99%

Population structure attributable to reproductive time: isolation by time and adaptation by time

2005

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“…Numerous studies have documented genetic and phenotypic variation through the season in samples of migrating or spawning anadromous salmonids (e.g., McGregor et al 1998;Smoker et al 1998;Brykov et al 1999;Hendry et al 1999;Woody et al 2000). Indeed, the timing of migration, maturation, and spawning all seem highly heritable (see citations in Hendry et al 1999).…”

Section: Interpreting Temporal Variationmentioning

confidence: 99%

Genetic and Phenotypic Variation through the Migratory Season Provides Evidence for Multiple Populations of Wild Steelhead in the Dean River, British Columbia

Hendry

Wenburg

Myers

et al. 2002

Transactions of the American Fisheries Society

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We provide evidence for previously undetected population structure in a wild run of summer steelhead Oncorhynchus mykiss within a river that has considerable recreational importance (Dean River, British Columbia). Data were gathered from an existing catch‐and‐release fishery and examined for phenotypic and genetic variation through the migratory season. Specifically, we compared fish captured in different periods during the migration: early (July 2‐30), middle (July 31‐September 5), and late (September 6‐30). Age (freshwater and saltwater), sex ratio, and body girth did not differ significantly among these groups for females or males. Body length increased through the migratory season for both sexes, perhaps because late‐migrating fish had more time to feed in the ocean. Based on genotypes at 10 microsatellite loci, early and late groups showed highly significant genetic differences (P < 0.001). Assignment tests were able to classify individuals back to early or late groups with 84% accuracy (122 of 145 tests). These results suggest the presence of at least two populations that migrate at different times in the Dean River system. The magnitude of the genetic difference was small (FST = 0.007; Nei's unbiased D = 0.0149, Reynolds coancestry coefficient = 0.007) but comparable to values for other anadromous Pacific salmon species over similar spatial scales. Moreover, the coarse level of our sampling, and possible overlap in migratory timing among populations, suggests that the observed differentiation underestimates the true differentiation. A deficit of heterozygotes in the late group suggests further population substructure within late‐migrating groups of fish. Examining temporal variation through a migratory season proved a useful approach for obtaining preliminary evidence of population structure in migrating salmonids within a small river system.

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“…Most reports of temporal divergence within a salmon population as evidence of local adaptation are confounded by potentially different spawning or rearing locations (e.g. Brykov et al 1999;Nielsen & Fountain 1999;Hendry et al 2002;Fillatre et al 2003) or do not include demonstrations of genetic divergence (Hendry et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Fine‐scale temporal adaptation within a salmonid population: mechanism and consequences

2013

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We demonstrate a clear example of local adaptation of seasonal timing of spawning and embryo development. The consequence is a population of pink salmon that is segmented into spawning groups that use the same limited habitat. We synthesize published observations with results of new analyses to demonstrate that genetic variation of these traits results in survival differentials related to that variation, and that density-dependent embryo mortality and seasonally variable juvenile mortality are a mechanism of selection. Most examples of local adaptation in natural systems depend on observed correlations between environments and fitness traits, but do not fully demonstrate local adaptation: that the trait is genetically determined, exhibits different fitness in common environments or across different environments, and its variation is mechanistically connected to fitness differences. The geographic or temporal scales of local adaptation often remain obscure. Here, we show that heritable, fine-scale differences of timing of reproductive migration in a pink salmon (Oncorhynchus gorbuscha) resulted in temporal structure that persisted several generations; the differences enable a density-dependent population to pack more spawners into limited spawning habitat, that is, enhance its fitness. A balanced trade-off of survivals results because embryos from early-migrating fish have a lower freshwater survival (harsh early physical conditions and disturbance by late spawners), but emigrant fry from late-migrating fish have lower marine survivals (timing of their vernal emergence into the estuarine environment). Such fine-scale local adaptations increase the genetic portfolio of the populations and may provide a buffer against the impacts of climate change.

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Analysis of mtDNA indicates weak temporal genetic heterogeneity in pink salmon spawning runs in two rivers on Sakhalin Island

Cited by 18 publications

References 28 publications

Population structure attributable to reproductive time: isolation by time and adaptation by time

Population structure attributable to reproductive time: isolation by time and adaptation by time

Genetic and Phenotypic Variation through the Migratory Season Provides Evidence for Multiple Populations of Wild Steelhead in the Dean River, British Columbia

Fine‐scale temporal adaptation within a salmonid population: mechanism and consequences

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