Practice Problem from last week

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Practice Problem from last week

• ATG CTA AAC GGA CAT TGT CAT GAT GGG CAC AGT
• ATA CTA AAT GGT CTT TGC AAT CAT GGA CAT AGC
• What are dN and dS for these two sequences? What
  does this suggest about their evolution?

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Ecological Genetics of Life Histories

• Evolution by natural selection has engineered all
  organisms for the same task reproduction

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If there were no limits to available energy

• The ideal organism would begin reproducing soon
  after birth, produce many, high quality
  offspring, and continue to reproduce
  indefinitely.

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• Although some organisms can do some of these
  things, no organism can do all of them.
• The reproductive capacity of all organisms is
  constrained by available energy

3-4 million eggs every 25 days
1-2 eggs per season
gt4500 years
1-2 days
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• Organisms must allocate a finite amount of energy
  to growth, reproduction, and maintenance.
• Leads to tradeoffs between these different needs.
• Different organisms have different patterns of
  allocation.
• Timing, amount, and periodicity of reproduction
  varies enormously among different organisms
• Even closely related organisms can vary a great
  deal in these patterns

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Life History

• The pattern of maturation, growth, reproduction,
  and aging that characterizes a group of organisms
• Life History Traits
• Egg-adult viability
• Maturation rate
• Mating success
• Fecundity
• Reproductive lifespan

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Life history of a holometabolous insect
Reproductive behavior Mating success Fertility Adu
lt lifespan
Egg viability
Egg development rate
Pupation success
Larval viability
Larval development rate
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Adult LH Traits

• Age-specific variation in reproduction and
  survival

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Questions

• Why have organisms evolved the particular
  life-histories they have?
• A female cod and a female trout of similar size
  may spawn similar egg masses. Yet the cod
  produces large numbers of small eggs and the
  trout produces small numbers of large eggs.
• Why do organisms have seemingly mal-adaptive
  life-histories
• birds have sub-optimal offspring number primates
  have very long juvenile periods most
  multicellular organisms experience senescence

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Life history of Virginia possum, Didelphis
virginiana
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Classic life-history questions
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How many offspring should an organism have?
Lacks hypothesis the number that will maximize
the number surviving
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Test of Lacks hypothesis suboptimal egg number
Parus major
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Solution 1 Tradeoffs b/w current future
reproduction
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Solution 2 Tradeoffs b/w offspring number
quality
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How big should each offspring be?
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Tradeoffs b/w offspring number size
Drosophila species, adjusted for differences in
body size r -0.80 Plt0.001
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Tradeoffs b/w offspring size quality
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How do tradeoffs constrain evolution?
Genetic Correlation
phen. corr genetic env corr. rP rA
rD rE R h2 S R1 h12 (b1 b2rA) R2
h22 (b2 b1rA)
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Negative genetic correlation between current and
future reproduction can explain sub-optimal
clutch size in Parus major.
Does this experiment demonstrate a negative
genetic correlation?
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Does this experiment demonstrate a negative
genetic correlation?
Fish taxa, adjusted for differences in
body size r -0.70 Plt0.001
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Correlations in Drosophila
Van der Linde 2003
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LH tradeoffs identified in studies of resemblance
among relatives (within populations)Poa annua
full-sib family means
Two different populations of meadow grass
inflorescenses in second season
inflorescenses in first season
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LH tradeoffs found in artificial selection
experiments (within populations)
(Partridge et al. 1999)
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