Genetic principles for captive breeding · 4 x N m x N f N m +N f 1 male 99 females N=100, Ne =...
Transcript of Genetic principles for captive breeding · 4 x N m x N f N m +N f 1 male 99 females N=100, Ne =...
Genetic principles for captive breeding
Zoos now and then
Success stories ex‐situ conservation?
Seed bank on Svalbard
Success stories ex‐situ conservation?
Arabian oryx
First species to reach Vulnerable conservation status (2011)after being extinct in the wild (1972)
Wild popualation: c. 1000Captive population: c. 6000
Breeding endangered animals
• Maximize the number of founders (unrelated animals).
• The population should as soon as possible reach the largest possible population size.
• The genetic contribution should be equal between the founders.
• Avoid inbreeding (maximize Ne)
• Maximize generation time.
• Do not mix populations of different genetic origin.
• Avoid selection.
Effective population size Ne
The size of an ideal population with the same rate ofinbreeding and/or genetic drift as the actualpopulation
Ne typically much smaller than N
Ne =4 x Nm x Nf
Nm + Nf
1 male99 femalesN=100, Ne = 3.96
2 males2 femalesN=4, Ne=4
Ne = 4
Ne =4N
Vk + 2
Ne decreases with increased variance in offspring
Ne
1= Ne1
1t1
Ne2
1Ne3
1( )* + + Net
1...
Ne over several generations are calculated by the harmonic mean.
The size of an ideal population with the same rate ofinbreeding and/or genetic drift as the actualpopulation
Ne typically much smaller than N
2Ne
1=ΔF
Pedigreesandinbreedingcalculations
Inbreeding
Matingofrelatedindividualsresultinginincreasedhomozygosityinprogeny(alleles
IdenticalByDescent‐ IBD).
Inbreedingdepression
Homozygosityofdeleteriousrecessiveallelesincreases.
Increasedoccurrenceofhereditarydisordersanddiseases.
Anoveralllossoffitness– survival,fertility,reproduction,productivity,performance,etc.
Inbreeding
Matingofrelatedindividualsresultinginincreasedhomozygosityinprogeny(AllelesIBD).
Inbreedingcoefficient(F):• Theprobabilitythattwoallelesatalocusareidenticalbydescent(IBD)
• Proportionoflociintheindividual’sgenomethathaveallelesidenticalbydescent(IBD)
Captivepopulationsarepedigreed
Name Dam Sire
BellaBaileyMollyMaxRoxie Bella BaileyCharlie Molly MaxGinger Roxie Charlie
Studbook
Bella Bailey Molly Max
Roxie Charlie
Ginger
Pedigree
female maledead
unknownsex
P‐generation(parental)
F1‐generation
F2‐generation
Glossary
Founders: individualsthathaveestablishedthepopulation(unrelatedindividualsinthepedigree)
Commonancestor:theancestorofbothmotherandfatheroftheindividualofinterest
Calculation
F=Σ (1/2)n *(1+Fca)
Calculation
Theprobabilitythatanalleleispassedontotheoffspring
numberofancestorsinthepedigree
Theinbreedingcoefficientofthecommonancestor
Coefficient of kinship (k)
• Degree of relatedness between two individuals.
• The inbreeding coefficient of a hypothetic offspring.
Kinship coefficients
• Self 0,5• Full sib 0,25• Parent‐offspring 0,25• Half sib 0,125• Uncle‐nephew 0,125• Cousin 0,0625
The inbreeding coefficient of a hypothetic offspring
Mean Kinship• Mean Kinship of an individual is the average of the kinship coefficient between that individual and all other living individuals in the populaiton (including itself).
• Low MK=few relatives=unique animal.
A B
C D
Mean Kinship
Mean kinship of C
Coefficient of kinship: Inbreeding coefficient of hypothetic offspring
A B
C D
Mean Kinship
Mean kinship of C
•C-A 0,25•C-B 0,25•C-D 0,25•C-C 0,5
0,5+3(0,25)
4=0,3125
Coefficient of kinship: Inbreeding coefficient of hypothetic offspring
Which golden lion tamarin is most valuable?
Thelma Louise Rita Robert Meankinship
Thelma 0.625 0.3125 0.125 0 0,27Louise 0.3125 0.625 0.125 0 0,27Rita 0.125 0.125 0.5 0 0,19Robert 0 0 0 0.625 0,16
Which golden lion tamarin is most valuable?
• Random loss of founder alleles because of limitednumber of offspring.
• Genetic variation smaller because of unequal foundercontribution.
Captive populations: Conserve genetic variation in founder
population.
Retention• The probability that a founder allele is still present in the populaiton.
Or…• The proportion of a founder´s genome that is still present in the population
ri = 1-p(loss)Calculations