Biology 2900 Principles of Evolution and Systematics

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Biology 2900Principles of Evolutionand
Systematics

• Dr. David Innes
• Jennifer Gosse
• Valerie Power

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Lunar Eclipse 2008
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Evolution in the News
Madagascar Ancient frog was as big as a bowling
ball Beelzebufo, or Devil Toad.

• http//www.cnn.com/2008/TECH/science/02/18/frog.fo
  ssil.ap/index.html

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Topics

• Adaptation
• Reproduction
• Sex and Sexual Selection
• Life-history evolution
• Diversity
• Classification and phylogeny
  (Lab 4)
• Species and speciation
• Patterns of evolution
• Evolution in the fossil record
• History of life on earth
• The geography of evolution
• The evolution of biodiversity

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Adaptation

• Sex and Sexual Selection
• - Mating success
• - Asymmetry in limits to
  reproductive success
• - Male competition, female
  choice
• Life-history evolution (Ch. 17)

?
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• Life History Evolution
• Evolution by natural selection has modified all
  organisms for one ultimate task
• to reproduce
• (sexual selection one aspect)
• How organisms carry out this task enormously
  diverse

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• Life History Diversity
• Mammals
• Mice mature early, reproduce quickly
• Bears mature late, reproduce slowly
• Plants
• annuals live 1 year then die
• perennials live gt 1 year
• Bivalves
• oyster 20 million eggs (0.05 mm)
• clam 100 eggs (0.30 mm)

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Kiwi egg 25 of females body weight
Cicada nymph stage 17 years
http//insects.ummz.lsa.umich.edu/fauna/Michigan_C
icadas/Michigan/Index.html
Aphid (parthenogenetic) telescopic generations
young develop offspring before they are born
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• Life History Evolution
• Organisms cant
• - mature at birth
• - produce high-quality offspring
• in large
  numbers
• - live forever
• Energy available for each activity finite
• trade-offs

and
and
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• Life History Evolution

Pattern of Energy Allocation Opossum Life-History
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• Life History Evolution
• Attempts to explain the diversity of
  reproductive strategies
• Trade-offs constrain the evolution of adaptations
• Balance costs and benefits to maximize
  reproductive success

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• Life History Evolution
• Environmental variation the source of much of the
  observed life-history variation
• Diversity of ways of surviving and reproducing
• Questions
• 1. Why do organisms age and die ?
• 2. How many offspring should be produced
  ?
• 3. How big should each offspring be ?

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• Life History Evolution
• Question
• Why do organisms age and die ?

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• Why do organisms age and die ?
• Aging (senescence)
• late-life decline in fertility and
  survival
• Aging reduces fitness and should be opposed by
  natural selection
• M. R. Rose (1991)
• Evolutionary Biology of
• Aging

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Reproduction and Aging (senescence)
Decline in survival and reproduction with age
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• Theories of Aging and Senescence
• 1. Rate-of-living theory
• 2. Evolutionary theory

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• Theories of Aging and Senescence
• Rate-of-living theory
• - aging caused by irreparable damage to cells
• and tissues (errors in replication
  accumulation of
• 
  metabolic by-products)
• Predictions
• (a) aging rate should be correlated
  with metabolic rate
• (b) selection not able to increase
  life span

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• Theories of Aging and senescence
• 1. Rate-of-living theory
• Prediction (a) high metabolic rate - shorter
  life span
• all species should expend about the same amount
  of energy per gram of tissue per lifetime
• - slowly over a long lifetime
• or - rapidly over a short lifetime
• Live fast die young

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Large amount of variation
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• Theories of Aging and Senescence
• Great Variation in metabolic rate among
  mammals
• - elephant shrew (36 kcal/g/per lifetime)
• - bat (1,102 kcal/g/per lifetime)
• Marsupials significantly lower metabolic rates
  and
• significantly lower life spans
• Variation in rate of living cannot explain
  variation in aging

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• Theories of Aging and senescence
• 1. Rate-of-living theory
• Prediction (b) longer life-span cannot be
  selected
• - no genetic variation for life-span

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Increased life span in Drosophila
Selection for increased life span
Select for early and late reproduction
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Aging and Senescence
http//www.cbc.ca/quirks/archives/05-06/jan28.html

Dr. Michael Rose http//www.mun.ca/biology/dinnes
/B2900/Rose.wav
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• Theories of Aging and Senescence
• 2. Evolutionary Theory of Aging
• aging caused by failure to repair cell and
  tissue damage
• Accumulation of deleterious mutations
• Trade-offs between repair and reproduction

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• Evolutionary Theory of Aging
• Simple Genetic Model
• (a) Wildtype matures at age 3 dies at age 16
• (b) Mutation matures at age 3 death at age 14
• (c) Mutation matures at age 2 death at age 10

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(a) Wild Type matures at age 3 dies at age 16
sum
RS reproductive success
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(b) Mutant matures at age 3 death at age 14
sum
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(c) Mutant matures at age 2 death at age 10
sum
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Summary
1
0.640
area
0.317
0.079
(a)
(b) 2.419 0.079 2.340
(c) 2.419 (0.0790.317) 0.640 2.663
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• Evolutionary Theory of Aging
• 
  Lifetime Repro.
• 
  Success
• (a) Wildtype
  2.419
• (b) Mutation earlier death 2.340
  (-3)
• (c) Mutation trade-off early 2.663
  (10)
• reproduction and early death

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• Evolutionary Theory of Aging
• Interpretation
• 1. deleterious mutations with effects late in
• life only weakly selected against
• 2. Mutations with benefits early in life and
• deleterious late in life favoured
• (antagonistic pleiotropy)
• trade-off between early reproduction and
  survival late in life

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Inbreeding depression and Age
If NS acts more weakly on late-acting deleterious
mutations then they will accumulate Evidence Inb
reeding depression increases with age
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Trade-off in Reproduction
Collared flycatcher Early reproduction Smaller
clutch size
Breed at age 2
Breed at age 1
Sample size
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Trade-off in Reproduction
Extra eggs
Female given extra eggs at age 1 show a decline
in clutch size
Control
Increased reproduction early in life ? decreased
reproduction later in life
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Trade-off between energy for reproduction and
later survival in plants
British grasses Annual gt than perennial Reproducti
ve effort proportion of biomass allocated to
flowers
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• Evolutionary Theory of Aging
• ETA can explain variation in life history
• Strength of Natural Selection declines
  late in life
• Question
• What is the relative importance
• of deleterious mutations and
• trade-offs in the evolution of
• senescence ?

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• Life History Evolution
• Questions
• 1. Why do organisms age and die ?
• 2. How many offspring should be produced
  ?
• 3. How big should each offspring be ?

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• 2. How many offspring to produce?
• Trade-off fixed amount of energy and time
• - the more offspring produced, the less time
  and energy to devote to each one

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• Clutch Size in Birds
• (David Lack, 1954)

Selection will favor the clutch size that
produces the most surviving offspring Assumption
probability of offspring survival decreases
with increasing clutch size (the
more kids, the less food for each)
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Clutch Size
Prob. of surviving (P) 0.5
of surviving offspring (CS x P) 5 x 0.5 2.5
Intermediate optimum
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• Test of Lacks hypothesis

Number of young surviving to breed
Great tit Parus major
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• Test of Lacks hypothesis

Fitness
Predicted 9 Observed 8.5
Based on a 23 year study
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• Clutch Size

Add or remove eggs to mothers clutch
Mothers clutch size affects daughters clutch
size
Optimum clutch size (maternal fitness) Maternal
survival, progeny survival and reproduction
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• 3. How big should each offspring be?
• Trade-off fixed amount of energy
• many small offspring or
• few large offspring
• Size number trade-off

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Fish Fruit
flies
Clutch Size
Egg Size
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Size number trade off
Goldenrods (Solidago)
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Size Number trade-off
Number
Example 2 size 5 offspring Each with prob.
0.8 Parental fitness 2 x 0.8 1.6
Prob. of offspring survival
Parental fitness
Evolution of shape of trade-off curves
Size
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• Selection on Offspring Size
• Example Side blotched lizard
• (surgical manipulation to increase egg size
  variation)
• Relationship between egg size
• Clutch size
• Progeny survival
• Maternal fitness

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Natural Small Large
EGG SIZE (Grams)
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• Results
• Clutch size decreased with increased egg size
• Progeny survival increased with egg size
• Maternal fitness highest for intermediate egg
  sizes
• Parent-offspring conflict
• Parent intermediate egg size
• Each offspring largest egg size

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• Life History Evolution

Summary Aging and Senescence trade-off
between reproduction and repair Offspring
number trade-off between clutch size and
offspring survival Offspring size
trade-off between offspring size and number
trade-off between offspring size and survival
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• Selection Thinking
• Natural Selection and Adaptation
• - reproduction
• - sex and sexual selection
• - life-history variation

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• Coming Next
• The History of the Diversity of Life