Estimates of natural selection in a salmon population in captive and natural environments.
ABSTRACT Captive breeding is a commonly used strategy for species conservation. One risk of captive breeding is domestication selection--selection for traits that are advantageous in captivity but deleterious in the wild. Domestication selection is of particular concern for species that are bred in captivity for many generations and that have a high potential to interbreed with wild populations. Domestication is understood conceptually at a broad level, but relatively little is known about how natural selection differs empirically between wild and captive environments. We used genetic parentage analysis to measure natural selection on time of migration, weight, and morphology for a coho salmon (Oncorhynchus kisutch) population that was subdivided into captive and natural components. Our goal was to determine whether natural selection acting on the traits we measured differed significantly between the captive and natural environments. For males, larger individuals were favored in both the captive and natural environments in all years of the study, indicating that selection on these traits in captivity was similar to that in the wild. For females, selection on weight was significantly stronger in the natural environment than in the captive environment in 1 year and similar in the 2 environments in 2 other years. In both environments, there was evidence of selection for later time of return for both males and females. Selection on measured traits other than weight and run timing was relatively weak. Our results are a concrete example of how estimates of natural selection during captivity can be used to evaluate this common risk of captive breeding programs.
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ABSTRACT: This thesis investigates the genetic structure among Atlantic salmon populations from France. We focused on the influence of environmental factors and stocking on the spatial distribution of genetic diversity. We genotyped 1739 individuals from 34 rivers at 17 microsatellite markers. Samples were collected in old (1965-1987) and recent (1998-2006) cohorts. Clustering analyses revealed the existence of five genetically and geographically distinct groups. Distance among estuaries and river length were strong predictors of population structure. Local adaptation to upstream migration difficulty linked to the large distance from the sea to the spawning grounds is suggested in the Loire-Allier population given the large body size of fish, their particular run timing, and the high differentiation of this population. Comparing recent and old samples revealed a general reduction of differentiation among populations and high introgression by stocking strains in some populations most probably resulting from stocking. In some depopulated rivers were no stocking was performed we observed natural recolonization by individuals from neighbouring and distant stocks. We developed an approach using temporally explicit simulations to quantify the impact of stocking on some populations. This study suggested a lower fitness of stocked fish compared to wild individuals. In parallel to genetic analyses, we carried out microchemistry analyses of otoliths from individuals collected in stocked populations. Coupling genetic and microchemistry analyses on the same individuals allowed identifying river-born fish with hatchery pedigrees, discriminating them from hatchery-born fish with similar genetic characteristics.12/2010, Degree: PhD, Supervisor: Bagliniere Guyomard Evanno Ourry
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ABSTRACT: One of the most challenging problems in evolutionary biology is linking the evolution of the phenotype with the underlying genotype, because most phenotypes are encoded by many genes that interact with each other and with the environment. Further, many phenotypes are correlated and selection on one can affect evolution of the other. This challenge is especially important in fishes, because their evolutionary response to harvest, global warming and conservation actions are among the least understood aspects of their management. Here, we discuss two major genetic approaches to studying the evolution of complex traits, multivariate quantitative genetics and molecular genetics, and examine the increasing interaction between the two fields. These interactions include using pedigree-based methods to study the evolution of multivariate traits in natural populations, comparing neutral and quantitative measures of population structure, and examining the contribution that the two approaches have made to each other. We then explore the major role that quantitative genetics is playing in two key issues in the conservation and management of fish populations: the evolutionary effects of fishing and adaptation to climate change. Throughout, we emphasize that it is important to anticipate the availability of improvements in molecular technology and statistical analyses by creating research populations such as inbred lines and families segregating at fitness traits, developing approaches to measuring the full range of phenotypes related to fitness, and collecting biological material and ecological data in natural populations. These steps will facilitate studies of the evolution of complex traits over informative temporal and spatial scales.Fish and Fisheries 11/2008; 9(4):396 - 422. · 5.86 Impact Factor
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ABSTRACT: Accumulating data indicate that hatchery fish have lower fitness in natural environments than wild fish. This fitness decline can occur very quickly, sometimes following only one or two generations of captive rearing. In this review, we summarize existing data on the fitness of hatchery fish in the wild, and we investigate the conditions under which rapid fitness declines can occur. The summary of studies to date suggests: nonlocal hatchery stocks consistently reproduce very poorly in the wild; hatchery stocks that use wild, local fish for captive propagation generally perform better than nonlocal stocks, but often worse than wild fish. However, the data above are from a limited number of studies and species, and more studies are needed before one can generalize further. We used a simple quantitative genetic model to evaluate whether domestication selection is a sufficient explanation for some observed rapid fitness declines. We show that if selection acts on a single trait, such rapid effects can be explained only when selection is very strong, both in captivity and in the wild, and when the heritability of the trait under selection is high. If selection acts on multiple traits throughout the life cycle, rapid fitness declines are plausible.Evolutionary Applications 04/2008; 1(2):342 - 355. · 4.15 Impact Factor