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.
- [Show abstract] [Hide abstract]
ABSTRACT: Captive breeding programs are a common approach to preventing extinction and rehabilitating endangered stocks of Pacific salmonids. To minimize inbreeding in these typically small populations, genetic data from microsatellite loci have been used to estimate relatedness and choose spawning pairs. Phenotypic attributes (e.g., body size), that result at least in part from environmental conditions during rearing likely affect reproductive outcome as well. However, the combined effects of individual phenotype and genetic broodstock management have not been previously evaluated. This study assessed the influence of genetic background (source of original broodstock collection, and heterozygosity of both male and female parents), the molecular genetic-derived relatedness coefficient of mated pairs, and phenotypic attributes of female parents (body size, ovulation rate) on reproductive outcome for three brood years of endangered coho salmon, Oncorhynchus kisutch, from the Russian River, California. Over 1200 full-sibling family groups were created in total, whose survival was tracked individually from fertilization through the swim-up fry stage. Strong maternal influence on reproductive outcome was found, as increased female body mass resulted in lower progeny survival rates, and higher ovulation rates predicted improved progeny survival. Male and female heterozygosity was generally positively related to embryo survival, but this effect was not consistently observed across brood years or early life stages. The relatedness coefficient between mated pairs had a significant and negative effect on progeny survival, particularly after hatching, even though the most inbred matings were prevented. Thus, use of genetic broodstock management to guide selection of salmon breeding pairs increases offspring survival, in addition to reducing inbreeding.Aquaculture 08/2013; s 404–405:95–104. · 1.83 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The Devils Hole pupfish is restricted to one wild population in a single aquifer-fed thermal pool in the Desert National Wildlife Refuge Complex. Since 1995 the pupfish has been in a nearly steady decline, where it was perched on the brink of extinction at 35-68 fish in 2013. A major strategy for conserving the pupfish has been the establishment of additional captive or "refuge" populations, but all ended in failure. In 2013 a new captive propagation facility designed specifically to breed pupfish was opened. I examine how a captive population can be initiated by removing fish from the wild without unduly accelerating extinction risk for the pupfish in Devils Hole. I construct a count-based PVA model, parameterized from estimates of the intrinsic rate of increase and its variance using counts in spring and fall from 1995-2013, to produce the first risk assessment for the pupfish. Median time to extinction was 26 and 27 years from spring and fall counts, respectively, and the probability of extinction in 20 years was 26-33%. Removing individuals in the fall had less risk to the wild population than harvest in spring. For both spring and fall harvest, risk increased rapidly when levels exceeded six adult pupfish per year for three years. Extinction risk was unaffected by the apportionment of total harvest among years. A demographic model was used to examine how removal of different stage classes affects the dynamics of the wild population based on reproductive value (RV) and elasticity. Removing eggs had the least impact on the pupfish in Devils Hole; RV of an adult was roughly 25 times that of an egg. To evaluate when it might be prudent to remove all pupfish from Devils Hole for captive breeding, I used the count-based model to examine how extinction risk related to pupfish population size. Risk accelerated when initial populations were less than 30 individuals. Results are discussed in relation to the challenges facing pupfish recovery compared to management of other highly endangered species.PeerJ. 01/2014; 2:e549.
- [Show abstract] [Hide abstract]
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