Effects of Supportive Breeding on the Genetically Effective Population Size

Ryman, Nils; Laikre, Linda

doi:10.1111/j.1523-1739.1991.tb00144.x

Cited by 474 publications

(470 citation statements)

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“…Finally, the relative reproductive success (x) of hatchery-born scallops was estimated using the Ryman-Laikre equation (See below, Ryman and Laikre, 1991) N W : effective population size of the recipient, wild population. N E : Effective population size of the resulting offspring from the mixing of the two populations.…”

Section: Discussionmentioning

confidence: 99%

“…As a consequence, enhancing wild populations with hatchery-born individuals can induce a reduction of their effective population size. This phenomenon is known as the Ryman-Laikre effect, which corresponds to the consequence of mixing populations with different effective population sizes (Ryman and Laikre, 1991;Ryman et al, 1995). This effect has been documented in a wide range of species (Utter and Epifanio, 2002) but has appeared to be minimal in bivalve mollusks in light of their population biology (Gaffney, 2006).…”

Section: Introductionmentioning

confidence: 99%

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Stock enhancement or sea ranching? Insights from monitoring the genetic diversity, relatedness and effective population size in a seeded great scallop population (Pecten maximus)

et al. 2016

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The mass release of hatchery-propagated stocks raises numerous questions concerning its efficiency in terms of local recruitment and effect on the genetic diversity of wild populations. A seeding program, consisting of mass release of hatchery-produced juveniles in the local naturally occurring population of great scallops (Pecten maximus L.), was initiated in the early 1980s in the Bay of Brest (France). The present study aims at evaluating whether this seeding program leads to actual population enhancement, with detectable effects on genetic diversity and effective population size, or consists of sea ranching with limited genetic consequences on the wild stock. To address this question, microsatellite-based genetic monitoring of three hatchery-born and naturally recruited populations was conducted over a 5-year period. Results showed a limited reduction in allelic richness but a strong alteration of allelic frequencies in hatchery populations, while genetic diversity appeared very stable over time in the wild populations. A temporal increase in relatedness was observed in both cultured stock and wild populations. Effective population size (Ne) estimates were low and variable in the wild population. Moreover, the application of the Ryman-Laikre model suggested a high contribution of hatchery-born scallops to the reproductive output of the wild population. Overall, the data suggest that the main objective of the seeding program, which is stock enhancement, is fulfilled. Moreover, gene flow from surrounding populations and/or the reproductive input of undetected sub-populations within the bay may buffer the Ryman-Laikre effect and ensure the retention of the local genetic variability.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Stock enhancement or sea ranching? Insights from monitoring the genetic diversity, relatedness and effective population size in a seeded great scallop population (Pecten maximus)

et al. 2016

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“…This paradox is overcome only when successful supportive breeding in augmenting the wild population is carried out over a long period of time such that the excessive drift and inbreeding in the initial generations of supportive breeding is compensated for by weaker drift and inbreeding in later generations because of the increase in census size. Ryman and Laikre (1991), Ryman et al (1995) and Wang and Ryman (2001) have provided approximations for the inbreeding and variance effective sizes, respectively, which can be different in this case, with one generation of supportive breeding. Nomura (1998a) obtained an expression of N e from the change in coancestry, which agrees with the variance effective size, as expected.…”

Section: Effective Population Size In Conservation Practicesmentioning

confidence: 99%

Prediction and estimation of effective population size

2016

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Effective population size (N e ) is a key parameter in population genetics. It has important applications in evolutionary biology, conservation genetics and plant and animal breeding, because it measures the rates of genetic drift and inbreeding and affects the efficacy of systematic evolutionary forces, such as mutation, selection and migration. We review the developments in predictive equations and estimation methodologies of effective size. In the prediction part, we focus on the equations for populations with different modes of reproduction, for populations under selection for unlinked or linked loci and for the specific applications to conservation genetics. In the estimation part, we focus on methods developed for estimating the current or recent effective size from molecular marker or sequence data. We discuss some underdeveloped areas in predicting and estimating N e for future research.Heredity ( INTRODUCTIONThe concept of effective population size, introduced by Sewall Wright (1931, 1933), is central to plant and animal breeding (Falconer and Mackay, 1996), conservation genetics (Frankham et al., 2010;Allendorf et al., 2013) and molecular variation and evolution (Charlesworth and Charlesworth, 2010), as it quantifies the magnitude of genetic drift and inbreeding in real-world populations. A substantial number of extensions to the basic theory and predictions were made since the seminal work of Wright, with main early developments by James Crow and Motoo Kimura (Kimura and Crow, 1963a;Crow and Kimura, 1970) and later by a list of contributors. Several review papers (Crow and Denniston, 1988;Caballero, 1994;Wang and Caballero, 1999;Nomura, 2005a) and population genetic books (Fisher, 1965;Wright, 1969;Ewens, 1979;Nagylaki, 1992) have summarised the existing theory in predicting the effective size of a population at different spatial and timescales under various inheritance modes and demographies. Comparatively, methodological developments (reviewed by Schwartz et al., 1999;Beaumont, 2003a;Wang, 2005;Palstra and Ruzzante, 2008;Luikart et al., 2010;Gilbert and Whitlock, 2015) in estimating the effective size of natural populations from genetic data lag behind but are accelerating in the past decade, thanks to the rapid developments of molecular biology.The classical developments of effective population size theory are based on the rate of change in gene frequency variance (genetic drift) or the rate of inbreeding. The effective population size is defined in reference to the Wright-Fisher idealised population, that is, a hypothetical population with very simplifying characteristics where genetic drift is the only factor in operation, and the dynamics of allelic and genotypic frequencies across generations merely depend on the population census (N) size. The effective size of a real population is then defined as the size of an idealised population, which would give rise to the rate of inbreeding and the rate of change in variance of gene frequencies actually observed in the population under consideration,

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“…It would obviously be important to identify the spawning grounds of these individuals in order to conduct more efficient sampling. However, it is likely that supportive breeding will need to be based on few fish, at least for the first generations, leading to a reduced overall effective population size and potentially inbreeding (Ryman & Laikre 1991).…”

Section:     mentioning

confidence: 99%

Genetic restoration of a stocked brown trout Salmo trutta population using microsatellite DNA analysis of historical and contemporary samples

Hansen¹,

Bekkevold²,

Jensen

et al. 2006

Journal of Applied Ecology

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Summary1. Gene flow from domesticated to wild populations is a major threat to wild salmonid fish. However, few studies have addressed how populations could be restored after admixture has occurred. We analysed the prospects for restoring the previously intensively stocked brown trout population of the Skjern River, Denmark, by identifying remaining nonadmixed individuals to be used for supportive breeding. 2. We analysed microsatellite DNA markers in historical (1940 -50s) and contemporary (1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004) samples from the Skjern River system, from the strain of domesticated trout previously used for stocking, and from the neighbouring Storå River. We analysed admixture proportions to estimate the genetic contribution by domesticated trout. We identified non-admixed trout using assignment tests, and further analysed the possible sources of indigenous trout by estimating contemporary migration among populations. 3. Genetic differentiation between the historical Storå and Skjern river populations was low ( θ ST = 0·004), suggesting considerable gene flow in the past. The contemporary Skjern and Storå river populations and a supportive breeding brood stock were strongly admixed, but some non-admixed individuals nevertheless remained in the wild-caught samples. In addition, two resident populations in isolated tributaries were found to be indigenous. The indigenous anadromous individuals from the Skjern River were unlikely to have been recruited from either the isolated tributary populations or the neighbouring Storå River and were presumably derived from unidentified spawning sites in the river system. 4. All but one non-admixed anadromous Skjern River trout were females, which we ascribed to sampling bias. Moreover, all non-admixed fish were late-spawning (JanuaryFebruary) whereas the majority of all trout caught for the study were ripe by NovemberDecember. The difference in spawning time could be an important factor delaying complete admixture of domesticated and indigenous trout. 5. Synthesis and applications. This study demonstrates the feasibility of restoring populations that have been admixed with exogenous individuals, by identifying non-admixed individuals using genetic markers. However, the results also highlight the problem that numbers of identified non-admixed individuals may be small, necessitating identification of nearby, closely related populations that can be incorporated into breeding programmes.

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Effects of Supportive Breeding on the Genetically Effective Population Size

Cited by 474 publications

References 18 publications

Stock enhancement or sea ranching? Insights from monitoring the genetic diversity, relatedness and effective population size in a seeded great scallop population (Pecten maximus)

Stock enhancement or sea ranching? Insights from monitoring the genetic diversity, relatedness and effective population size in a seeded great scallop population (Pecten maximus)

Prediction and estimation of effective population size

Genetic restoration of a stocked brown trout Salmo trutta population using microsatellite DNA analysis of historical and contemporary samples

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