1. Darwin
Genetics
Population Genetics and The Modern Synthesis
Modern Evolutionary Theory
A. Peripatric Speciation

2. Population Genetics and The Modern Synthesis
Darwin
Genetics
Population Genetics and The Modern Synthesis
Modern Evolutionary Theory
A. Peripatric Speciation
B. Punctuated Equilibrium
Niles Eldridge
Stephen J. Gould

3. B. Punctuated Equilibrium – Eldridge and Gould
1. Consider a large, well-adapted population
VARIATION
TIME

4. B. Punctuated Equilibrium – Eldridge and Gould
1. Consider a large, well-adapted population
Effects of Selection and Drift are small - little change over time
VARIATION
TIME

5. B. Punctuated Equilibrium – Eldridge and Gould
2. There are always small sub-populations "budding off" along the periphery of a species range...
VARIATION
TIME

6. X X X B. Punctuated Equilibrium – Eldridge and Gould
2. Most will go extinct, but some may survive...
VARIATION X X X
TIME

7. X X X B. Punctuated Equilibrium – Eldridge and Gould
2. These surviving populations will initially be small, and in a new environment...so the effects of Selection and Drift should be strong...
VARIATION X X X
TIME

8. X X X B. Punctuated Equilibrium – Eldridge and Gould
3. These populations will change rapidly in response...
VARIATION X X X
TIME

9. X X X B. Punctuated Equilibrium – Eldridge and Gould
3. These populations will change rapidly in response... and as they adapt (in response to selection), their populations should increase in size (because of increasing reproductive success, by definition).
VARIATION X X X
TIME

10. X X X B. Punctuated Equilibrium – Eldridge and Gould
3. As population increases in size, effects of drift decline... and as a population becomes better adapted, the effects of selection decline... so the rate of evolutionary change declines...
VARIATION X X X
TIME

11. X X X B. Punctuated Equilibrium – Eldridge and Gould
4. And we have large, well-adapted populations that will remain static as long as the environment is stable...
VARIATION X X X
TIME

12. X X X B. Punctuated Equilibrium – Eldridge and Gould
5. Since small, short-lived populations are less likely to leave a fossil, the fossil record can appear 'discontinuous' or 'imperfect'
VARIATION X X X
TIME

13. X X X B. Punctuated Equilibrium – Eldridge and Gould
5. Large pop's may leave a fossil....
VARIATION X X X
TIME

14. X X X B. Punctuated Equilibrium – Eldridge and Gould
5. Small, short-lived populations probably won't...
VARIATION X X X
TIME

15. X X X B. Punctuated Equilibrium – Eldridge and Gould
6. So, the discontinuity in the fossil record is an expected result of our modern understanding of how evolution and speciation occur...
VARIATION X X X
TIME

16. X X X B. Punctuated Equilibrium – Eldridge and Gould
6. both in time (as we see), and in SPACE (as changing populations are probably NOT in same place as ancestral species).
VARIATION X X X
TIME

17. Population Genetics and The Modern Synthesis
Darwin
Genetics
Population Genetics and The Modern Synthesis
Modern Evolutionary Theory
A. Peripatric Speciation
B. Punctuated Equilibrium
C. Genes and Development: “Evo-Devo”
…explain changes like this?
Can changes like this….

18. C. Genes and Development: "Evo-Devo"
…explain changes like this?
Can changes like this….
Differences correlate with what they make (different proteins make them different colors)
Differences don’t correlate with what they make; they are pretty much the same stuff, just in a different shape.

19. C. Genes and Development: "Evo-Devo"

20. C. Evo-Devo – the influence of regulatory genes

21. Without Fish
With Fish
Antennules detect chemicals secreted by predatory fish
Stimulate release of dopamine in the brain
Brain releases juvenile hormone (growth hormone in inverts)
Growth of particular body parts continues, creating a sharp “helmet” and longer “spine” that reduce predation.
Selection for an inducible developmental pathway

22. Modern Evolutionary Theory A. Peripatric Speciation
B. Punctuated Equilibrium
C. Genes and Development: “Evo-Devo”
D. Model
Sources of Variation Agents of Change
Mutation Natural Selection
Recombination Drift
- crossing over Mutation
- independent assortment Migration
Non-random Mating
VARIATION D E V L O P M N T

23. Evolution
Selection

24. A. ‘Artificial Selection’ and Domesticated Animals and Plants

25. A. ‘Artificial Selection’ and Domesticated Animals and Plants

26. A. ‘Artificial Selection’ and Domesticated Animals and Plants

27. A. ‘Artificial Selection’ and Domesticated Animals and Plants

28. A. ‘Artificial Selection’ and Domesticated Animals and Plants

29. A. ‘Artificial Selection’ and Domesticated Animals and Plants
Selection can create phenotypes beyond the initial range of expression.. There are no adult wolves as small as chihuahuas.

30. Selection for change in energy allocation
- from vegetative tissue to reproductive tissue

31. Matsuoka, et al A single domestication for maize shown by multilocus microsatellite genotyping. PNAS 99:

32. Selection in wild mustard

33. II. Selection
B. Natural Selection
- Types of Selection

34. II. Natural Selection B. Natural Selection - Types of Selection
Stabilizing selection for size at birth in humans

35. II. Natural Selection B. Natural Selection - Types of Selection
Directional selection for beak size

36. Kettlewell, 1956

38. Speciation
- Allopatric:
The result of geographic isolation and subsequent divergence; often because of b-directional selection for different traits in different environments (corollary)
ENV 1
ENV 2
Directional
Directional
Separate Populations

39. II. Natural Selection B. Natural Selection - Types of Selection
Disruptive selection for beak width in African finches feeding on two species of sedges with soft and hard seeds.
Same Population

40. Spadefoot toad mouthparts

41. Can result in sympatric speciation – speciation within a reproducing population, in which different subpopulations become adapted to different niches in the same environment and produce poorly adapted hybrids when they breed with other subpopulations.

42. Sympatric Speciation through polyploidy (mutation, not selection)
Normal diploid species, mutant diploid gamete
Normal diploid species, haploid gamete

43. II. Natural Selection B. Modes of Selection Natural Selection
Sexual Selection: fitness of a genotype/trait depends on organism’s sex

44. II. Natural Selection B. Modes of Selection Natural Selection
Sexual Selection: fitness of a genotype/trait depends on sex
Kin Selection: fitness depends on relatedness within group

45. II. Natural Selection B. Modes of Selection Natural Selection
Sexual Selection: fitness of a genotype/trait depends on sex
Kin Selection: fitness depends on relatedness within group
Frequency-dependent Selection: fitness depends on genotype frequency
Papilio memnon females have many possible phenotypes that mimic toxic species. Abundant morphs are selected against; because bird predators learn they are tasty and prey on them. Negative frequency dependence.
females

46. II. Natural Selection B. Modes of Selection Natural Selection
Sexual Selection: fitness of a genotype/trait depends on sex
Kin Selection: fitness depends on relatedness within group
Frequency-dependent Selection: fitness depends on genotype frequency
Female guppies prefer to mate with the rarest male phenotype; selects for polymorphism over time – Negative Frequency dependent selection

47. II. Natural Selection B. Modes of Selection Natural Selection
Sexual Selection: fitness of a genotype/trait depends on sex
Kin Selection: fitness depends on relatedness within group
Frequency-dependent Selection: fitness depends on genotype frequency
Heliconius erato is a toxic species in Central America. Whichever morph becomes more abundant (even by chance) becomes EVEN MORE abundant because birds learn to avoid it more readily. Positive frequency dependence.

48. II. Natural Selection Artificial Selection Modes of Selection
C. Testing for Selection/Adaptation
1. Phenotypic Plasticity
Why do populations differ?
Genetic adaptation (selection)
Evolutionary diverge due to other agents of change (drift)
Phenotypic plasticity – the direct effect of environment on phenotype

49. Daphnia grow spines and head-spines when developing in the presence of fish (predators)
Are these changes ‘adaptations’, or is one genome ‘acclimating’ to different environments? And is this ‘acclimation’ itself an adaptation?
Gastrimargus grasshoppers developing in different seasons (with predictable sustrate colors) develop into different colored nymphs and adults

50. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?

51. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
So, suppose we observe variation in plant size among genetically different plants growing in a field:
This variation in phenotype might be due to a combination of genetic and environmental differences between them.
V(phen) = V(env) + V(gen)

52. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
IF these plants were all grown under the same environmental conditions (‘common garden’ experiment), then there is no variation in the environment and the variation we observe can be attributed to genetic differences.
V(phen) = 0 + V(gen)
(whether these genetic differences are ADAPTIVE is another question…)

53. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
IF these plants were all grown under the same environmental conditions (‘common garden’ experiment), then there is no variation in the environment and the variation we observe can be attributed to genetic differences.
V(phen) = 0 + V(gen)
(But this is only true for this environment!)

54. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
In a different environment, phenotypic and genetic variation may be expressed differently.

55. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
So, in a large population experiencing a range of environments:
V(phen) = V(env) + V(gen) + V(g*e)
V(g*e) is a genotype by environment interaction; reflecting the fact that genotypes may respond in different ways to changes in the environment.

56. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
Suppose we had populations of each genotype, and these were the mean heights of these populations.
Genotype C F
Height
Stanford
Mather
Environment

57. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
Suppose we had populations of each genotype, and these were the mean heights of these populations.
Genotype C F
Height XS
V(env) XM
Stanford
Mather
Environment

58. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
Suppose we had populations of each genotype, and these were the mean heights of these populations.
Genotype C F
Height XC
V(gen) XF
Stanford
Mather
Environment

59. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
Suppose we had populations of each genotype, and these were the mean heights of these populations.
Genotype C F
Height
XCS
XCM =
XFS
XFM
The effect of environment IS THE SAME for the two genotypes:
(g*e) = 0.
Stanford
Mather
Environment

60. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
So, in this comparison:
V(phen) = V(env) + V(gen) + V(g*e)
Sig. Sig. ns

61. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
Suppose we compare B and E.
Genotype B E
Height
Stanford
Mather
Environment

62. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
Environmental effects are significant
Genotype B E
Height XS
V(env) XM
Stanford
Mather
Environment

63. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
Genetic effects are insignificant; means don’t differ.
Genotype B E
Height XC XE
V(gen) = 0
Stanford
Mather
Environment

64. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
There is a significant ‘G x E’ interaction.
Genotype B E
Height
XCS
XCM
>>
XFS
XFM
The effect of environment IS NOT THE SAME for the two genotypes!!
Stanford
Mather
Environment

65. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
In a different environment, phenotypic and genetic variation may be expressed differently.
So, in this comparison:
V(phen) = V(env) + V(gen) + V(g*e)
Sig. ns Sig.

66. We should expect adaptations to specific environmental conditions to be reflected by such “genotype by environment” interactions in characters that affect reproductive success.

67. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
Selection for Acclimation Ability

68. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
Selection for Acclimation Ability
Raised at 20oC
Raised at 45oC

69. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
Selection for Acclimation Ability
How could we test whether this is an environmental effect or a genetically adaptive pattern of acclimation?

70. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
Selection for Acclimation Ability
How could we test whether this is an environmental effect or a genetically adaptive pattern of acclimation?
Do other populations from aseasonal areas respond the same way, phenotypically.

71. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
Selection for Acclimation Ability
Is the development of spines and head shields strictly environmentally induced, or is it a developmental adaptation?
Introduce Daphnia that have never experienced fish… do they grow head shields?

72. II. Natural Selection C. Testing for Selection/Adaptation
Phenotypic Plasticity
Genetics, environment, or genetic adaptation to environment?
Selection for Acclimation Ability
Is the development of spines and head shields strictly environmentally induced, or is it a developmental adaptation?
Introduce Daphnia that have never experienced fish… do they grow head shields?
HOW do these acclimation adaptations evolve? Are there NEW structural genes that evolve?

73. Sources of Variation Agents of Change Mutation Natural Selection
No. The difference is how they are modulated/regulated. Always on, always off, or developmentally dependent on environmental conditions.
D. Model
Sources of Variation Agents of Change
Mutation Natural Selection
Recombination Drift
- crossing over Mutation
- independent assortment Migration
Non-random Mating
VARIATION D E V L O P M N T