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Paper 2: Genetic management of captive populations: the advantages
of…
Paper 2: Genetic management of captive populations: the advantages
of circular mating (Theodorou & Couvet, 2010
Results
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Genetic variability
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circular mating minimizes the mean pairwise coancestry for all population sizes and time-lengths of the management program
Circular mating increases the present level of homozygosity, the low mean pairwise coancestry in combination with the lower number of lethal equivalent. Single generstion of outcrossing should suffice to restore both gene diversity and population fitness.
Introduction to the wild
The decrease in the probability of extinction of a population released to the wild after 20 generations of circular mating.
The advantages of circular mating holds for all population sizes and net reproductive rates examined. The simulations prior to reintroduction to the wild, the released population gain important benefits by the implementation of circular mating.
The deleterious alleles increase rapidly the genetic load of the released population and drive them to a more rapid extinction.
Method
Loci to subject
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Assumed deleterious mutation falls into 2 classes
- slightly deleterious partly recessive alleles with dominance and selection coefficients
- high recessive lethal mutations
Population which survive through mutation and selection will be randomly chosen to form an initial population
Neutral variation
200 freely recombining neutral loci are assumed to check whether the measures using pedigree information concord with those obtained at the gene level
Initial population: 2N alleles (N= population size), therefore heterozygosity equals 1
Allelic diversity is calculated at given population as 100% of alleles remaining in the population/initial number of alleles averaged over loci and replicates
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Management procedures
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In all breeding schemes, mutation, reproduction and viability selection are the succession of events
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Comparison of unmanaged population with the method proposed by Fernández and Caballero (Gc/mc and circular mating
Gc/mc
2 steps
Step 1:contribution of each parent in the next generation was chosen in such a way that group coancestry of the offspring was minimized, followed by "simulated annealing"
Step 2: the combination of matings that yielded the lowest average of pairwise coancestry between couples using "Hungarian algorithm"
One of the viable offspring was used to form the next generation while the other viable offspring formed the stock pool which to be used subsequently
If a couple did not produce any viable offspring, a viable one from the other couples will be chosen (individuals that confer to the population the minimum mean pairwise coancestry)
If no extra viable offspring was produced then the population declines until extinction eventually occurs
Circular mating
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If a couple did not produce any viable offspring, an individual that shared one of the parents with the "childless" couple
If such an offspring did not exist, one will chosen randomly in the stock pool
If the individual in the stock cannot replace the number of failures, population size decreases until extinction eventually occurs.
Random mating
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Procedure of viability selection and offspring production is identical to that described for Gc/mc procedure
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