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