Animal domestication

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Animal domestication

• Evolutionary Applications course, module 3a,
  24.01.2008
• Anti Vasemägi, anti.vasemagi_at_utu.fi
• http//users.utu.fi/antvas/

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Overview

• Which species, when, where, how many times?
• Genetic basis of domestication
• Factors determining adaptation to captivity
• Advertent and inadvertent effects of
  domestication (captive breeding)
• Domestic-animal genomics

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Domestication

• the process by which captive animals adapt to
  man and the environment he provides Price 1984
• refers to the process whereby a population of
  animals or plants becomes accustomed to human
  provision and control
• The process of genetically adapting an animal or
  plant to better suit the needs of human beings.
  Brufford et al. 2003

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Domestication problems with the definitions

• Domestic Wild category represents just the
  extremes of the process
• Feral organisms that escaped domestication and
  returned, partly or wholly, to its natural state.

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Domestication as a proof of evolution

• C. Darwin (1883) The Variation in Animals and
  Plants under Domestication. New York D. Appleton
  Co.  
• http//www.esp.org/books/darwin/variation/facsimil
  e/title3.html

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Domestication not so frequent after all

• Among 148 non-carnivorous mammals weigting more
  than 45kg, 14 have been domesticated (many
  different reasons, e.g. Gazelles panic in
  enclosures)
• Birds 10 out of 10 000 being domesticated
• Fish only carp (Cyprinus carpio)
• simply rearing organism is not enough

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Domestication when it happen?
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Domestication where?
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Domestication how many times?
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Phylogeny of modern- day cattle

• Based on 201 bp of mtDNA control-region

Aurocks Extinct 1627
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Sheep domestication

• mtDNA ML phylogeny based on 1045bp control-region
  sequence

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Genetic view of domestication
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• The extent of adaptation to captivity
  (domestication) depends upon
• genetic diversity
• selection intensity
• III) effective population size
• IV) number of generation in captivity

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• The extent of adaptation to captivity
  (domestication) depends upon
• genetic diversity
• selection intensity
• III) effective population size
• IV) number of generation in captivity

Intentional selection Unintentional
selection Relaxation of selection
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Unintentional selection

• Many traits are correlated to each other, one
  trait affected by many genes
• By selecting against aggression in foxes for 40
  years additional changes never deliberately
  selected appeared spotted coat, drooping ears,
  shortened snouts and tail.

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Relaxation of selection

• As captive environment is more benign compared to
  wild slightly deleterious mutations are not
  removed from the population
• (relaxation of selective constraint).

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Phylogenetic tree of wolf, dog and coyote

• Phylogenetic tree of wolf (W), dog (D), and
  coyote (C) mtDNA sequences.
• Internal dog branches are marked in orange, and
  internal wolf branches are marked in light blue

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Dn/Ds ratio in wolf, dog coyote
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Factors determining adaptation to captivity

• The cumulate genetic change in reproductive
  fitness in captivity over t generations (GAt) can
  be predicted from the breeders equation
• S is the selection differential, h2 the
  heritability, Ne effective population size, and t
  the number of generations in captivity.
• Sh2 is the response to selection in the first
  generation.

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Predictions from breeders equation

• We predict that genetic adaptation to captivity
  will be positively related to intensity of
  selection, genetic diversity, effective
  population size and number of generations.

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Adaptation to captivity two- edged sword

• The genetic variants favored in captivity usually
  differ from those favored in natural
  environments.
• Selection for tameness and other adaptations to
  the captive environment are often inevitable
• Such characters are usually highly appreciated
  among animal breeders
• In species conservation programs adaptation to
  captivity is expected to have major effects on
  reintroduction success for species (Frankham
  2007)
• Characteristics selected for under-captive
  conditions are overwhelmingly disadvantageous in
  the natural environment

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Humans have a tendency for unintentionally
selecting against what they desire most.
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Empirical evidence on adaptation to captivity

• (i) the genetic basis of adaptive changes in
  captivity,
• (ii) factors affecting the extent of genetic
  adaptation to captivity
• (iii) means for minimizing its deleterious
  impacts.

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The extent of adaptation to captivity may be
large

• After 25 generations wild rat (Rattus norvegicus)
  showed 55 earlier age at first reproduction
• More than doubled duration of reproductive life
• Almost three-times as many litters
• Fecundity in captivity of a large white butterfly
  (Pieris brassicae) population that had been in
  captivity for 100150 generation was about
  13-fold higher than that in a new wild strain
  (Lewis Thomas 2001).

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Reported evolutionary change in farmed fish
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Traits selected for under-captive conditions are
disadvantageous in wild

• This effect has been reported for turkeys,
  amphibians, plants and many species of fish
• Farmed salmon had a fitness only 16 that of wild
  fish in the study by Fleming et al . (2000) and
  24 in McGinnity et al. (2003).

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Genetic basis of adaptation to captivity

• Rare, deleterious and partially recessive alleles
  in wild are expected to form the main basis of
  genetic adaptation to captivity.

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Means for minimizing the deleterious effects of
adaptation to captivity

• We predict that genetic adaptation can be
  minimized by
• (i) minimizing generations in captivity
• (cryopreservation, delay of reproduction)
• (ii) minimizing selection
• (making captive environment similar to wild,
  equalizing family sizes)
• (iii) minimizing genetic diversity
• (Reducing genetic diversity by fragmentation)
• (iv) minimizing effective population size.
• In addition, immigration from the wild to
  captivity reduces genetic adaptation

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Intensity of selection and rate of adaptation to
captivity in Drosophila.
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Effect of fragmentation of captive populations
fitness in wild
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Domestic-animal genomics hunt for the holy grail
- QTNs
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Shared characteristics and the possibility of
domestication genes
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Endocrine system as a candidate pathway for
domestication?
untreated
Traits in hypothyroid rat smaller overall size,
shorter muzzle, floppy ears, are superficially
similar to traits shared by many domestic animals.
hypothyroidic
This correlation suggests a possible role for
thyroid hormone during the process of
domestication
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Domestic animal genomics monogenic trait success
stories I
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Domestic animal genomics monogenic trait success
stories II
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Genome-wide association mapping of mendelian
traits

• 27 000 SNPs
• Only using 20 dogs!

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(No Transcript)
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Fine-mapping of coat color in boxers and bull
terriers
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Dissection of complex traits I
IGF QTN increases muscle mass only 3-4
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Dissection of complex traits II

• A point mutation that creates an illegitimate
  microRNA target in the 3' UTR of myostatin,
  inhibits its expression and contributes to the
  muscular hypertrophy of Texel sheep.
• QTNs not always amino acid changing substitutions

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Complex-trait dissection via QTL mapping and
transcriptomics
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Proposal I for the Discussion (module3b)
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Proposal II for the Discussion (module3b)
C. Darwin 1868
http//www.esp.org/books/darwin/variation/facsimil
e/title3.html