Plasticity and G?E

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Plasticity and G?E in Evolutionary Genetics
Gerdien de Jong Utrecht University
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Overview talk

• phenotypic plasticity
• selection gradient
• predictable selection
• unpredictable selection
• life history complications
• density
• zygote migration

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Phenotypic Plasticity
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phenotypic plasticity
Drosophila melanogaster
a systematic change in morphology of an organism
due to a developmental response to
environmental conditions
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phenotypic plasticity
Drosophila wing length
reaction norm genotype represents a
function genotypic value is function value
in given environment function value character
state
temperature
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phenotypic plasticity
Drosophila wing length
Genotype-by-Environment Interaction
G?E reaction norms different slope or shape
temperature
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phenotypic plasticity
Genotype-by-Environment Interaction
G?E genetically large low temperature genetically
small high temperature
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phenotypic plasticity
Genotype-by-Environment Interaction Drosophila
melanogaster two populations tropical
temperate two temperatures 17.5C 27.5C
IN body size adults gene expression pupation
probability larval glycogen level development
time larval competitive ability female fecundity
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Selection Gradient
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multivariate selection

• phenotypic trait i zi gi ei
• vector of changes in phenotypic means ? z
• phenotypic variance covariance matrix P

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selection gradient
One trait Selection differential equals the
covariance between phenotype zi and fitness
w Selection gradient equals the slope of
fitness on phenotype
?z,i cov(zi,w)/var(zi)
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selection gradient
One trait Selection gradient equals the slope of
fitness on phenotype Selection gradient equals
the derivative of fitness towards phenotype
?z,i cov(zi,w)/var(zi)
?w/?zi ?z,i
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multivariate selection

• phenotypic selection gradient each trai t
• multivariate phenotypic selection
  

?w/?zi ?z,i
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multivariate selection

• genotypic value trait i gi
• vector of changes in genotypic means ? g
• genotypic variance covariance matrix G

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multivariate selection

• genotypic selection gradient each trait
• multivariate genotypic selection
  

?w/?gi ?g,i
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multivariate selection
Evolutionary Biology ?z ?g ? g G
?z phenotypic plasticity multivariate
traits character states reaction norm
coefficients
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Predictable Selection
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predictable selection
zygote pool z1 mating pool selection in
x zygote pool z0
life history
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character state
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character state
in environment x all selection gradients 2fx
s(?x-gx)0 selection finds optimum character
state in each x gx ?x
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Unpredictable Selection
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unpredictable selection
life history
zygote pool z1 mating pool selection in y adult
migration development x zygote pool z0
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unpredictable selection
migration frequency from x to y f(yx)
?y1
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unpredictable selection
selection gradient for phenotype that should
develop in environment x weighted
average! (weak selection)
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unpredictable selection
evolved phenotypic mean character state
(weak selection)
evolved mean phenotype g00.3
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unpredictable selection
evolved phenotypic mean character state
(weak selection)
compromise phenotype evolves
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unpredictable selection
evolved phenotypic mean reaction
normcoefficients height at x0
slope (weak selection)
compromise phenotype evolves
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unpredictable selection
evolved reaction norm slope shallower than
optimal slope if reacton norm linear
and few environments or asymmetrical migration
compromise phenotype evolves
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unpredictable selection
optimum reaction norm slope ? 1
evolved reaction norm slope ? 1 cov(x,y)/var(x)
environment value
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Life History Complications
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Life History Complications density dependence
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density dependent numbers
zygote pool z1 mating pool density dependence
c selection in y density dependence b adult
migration density dependence a development
x zygote pool z0
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density dependent numbers
frequency environments now includes density
dependent viability vy in environments y
fx,y fx,y vy Effective frequency of selection
environments can become complicated
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density dependent numbers
equal density depence leads to evolved mean
genotypic values reflecting the frequencies of
the environment, y00.3 and y10.7
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density dependent numbers
density dependence in y1 gets so high that nobody
survives in environment y1 effectively only
environment y0 exists
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Life History Complications zygote migration
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no zygote pool
zygote migration mating pool density dependence
c selection in y density dependence b adult
migration density dependence a development
x zygote migration
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no zygote pool
if both zygotes and adults migrate, selection
equations only approximate requires matrix
methods introduces reproductive value in
evolved genotypic value
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no zygote pool
if zygotes migrate but adults not, and selection
is predictable zygote migration gives no
problem
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conclusions
Selection on phenotypic plasticity is efficient
if selection predictable no adult migration and
therefore no life history complication
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