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Evolution of functional traits (Joel Kingsolver, Biology) Traits as functions: functional, function- valued, infinite-dimensional A primer in evolutionary models: –Variation, inheritance, selection, evolution Approaches to analysing functional traits: –understanding genetic variation –Estimating selection –Predicting evolutionary responses & constraints
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Examples of functional traits Functions of age: –growth trajectories; life history; aging Functions of environmental state: –Physiological ‘reaction norms’ Descriptions of 2-D or 3-D shape, etc
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Age-specific mortality rates (Drosophila) Pletcher et al, Genetics (1999)
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Evolution of quantitative traits: some basics Individual organism: –Phenotype: observable trait with value z –Genotype: genetic ‘type’ (usually inferred) Population: –Phenotypic variance, P = G + E –Genetic variance, G Evolution = change in mean trait value per generation, z
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Evolution, in 3 easy steps P Trait value z Frequency z
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Evolution, in 3 easy steps (2) Trait value z Frequency z z’
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Evolution, in 3 easy steps (3) Trait value z Frequency z z’ zz
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A simple evolutionary model Variation and inheritance –Variance: P = G + E Selection –Selection gradient: = P -1 ( z’ - z ) –Also: = d[ln(W)]/dz, where W = mean population fitness Evolutionary response – z = G
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Evolution on an adaptive landscape Mean phenotype, z Mean fitness, W
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z = G z may be: a scalar a vector a function z(t) = G(t,s) s ds
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Analysing genetics of functional traits Estimating G: an example Biological hypotheses about G: eigenfunction analysis G and the response to selection
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Temperature & caterpillar growth rates: Thermal performance curves (TPCs) z(t), where t = temperature
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GeneticVar-Cov for RGR
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Basis = orthogonal polynomials
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Analysing genetics of functional traits Estimating G: an example Biological hypotheses about G: eigenfunction analysis G and the response to selection
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Faster- slower Hotter- colder Generalist- specialist
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Eigenfunction Faster- slower Hotter- colder Generalist- specialist
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Caterpillar growth rates
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Temperature Performance Hotter-Colder II
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G-covariance function: Variation in TPC position
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First eigenfunction (65%)
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Second eigenfunction (25%)
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Analysing genetics of functional traits Estimating G: an example Biological hypotheses about G: eigenfunction analysis G and the response to selection
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Eigenfunction Faster- slower Hotter- colder Generalist- specialist
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Evolutionary Constraints: Identifying zero eigenfunctions
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Selection and evolutionary response Estimating selection, (s): an example Predicting evolutionary responses
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Selection on caterpillar growth rate TPCs Measure z(t) for a sample of individuals in the lab --> estimate P(s,t) Measure fitness of those individuals in the field Estimate (s) (cubic splines)
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Evolutionary Response to Selection Selection Evolutionary response Evolutionary change in one generation
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Challenges Estimation methods for G Hypothesis testing of eigenfunctions Estimating zero eigenfunctions Estimation methods for Predicting evolutionary responses
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