1. BIOE 109
Summer 2009
Lecture 9- Part II
Kin selection

2. Types of social interactions
“Actor”  “Recipient”   
 outcome of interaction measured in terms of fitness
i.e. units of surviving offspring
Actor benefits Actor harmed
Recipient
benefits
harmed

3. Types of social interactions i.e. units of surviving offspring
“Actor”  “Recipient”   
 outcome of interaction measured in terms of fitness
i.e. units of surviving offspring
Actor benefits Actor harmed
Recipient Cooperative
benefits
Recipient
harmed

4. Types of social interactions
“Actor”  “Recipient”   
Actor benefits Actor harmed
Recipient Cooperative Altruistic
benefits
Recipient
harmed

5. Types of social interactions
“Actor”  “Recipient”   
Actor benefits Actor harmed
Recipient Cooperative Altruistic
benefits
Recipient Selfish
harmed

6. Types of social interactions
“Actor”  “Recipient”   
Actor benefits Actor harmed
Recipient Cooperative Altruistic
benefits
Recipient Selfish Spiteful
harmed

7. Types of social interactions
“Actor”  “Recipient”   
Actor benefits Actor harmed
Recipient Cooperative Altruistic
benefits
Recipient Selfish Spiteful
harmed
Rare -an allele that results in fitness losses
for both R&A would be eliminated by
Natural selection

8. Types of social interactions
“Actor”  “Recipient”   
Actor benefits Actor harmed
Recipient Cooperative Altruistic
benefits
Recipient Selfish Spiteful
harmed

9. Co-operation and altruism

10. The evolution of altruism
• an altruistic act benefits a recipient at a cost to the actor

11. The evolution of altruism
• an altruistic act benefits a recipient at a cost to the actor
• Why does altruism exist in nature?
how can altruistic behaviors evolve?

12. Bill Hamilton (1936 – 2000)

13. The evolution of altruism
• an altruistic act benefits a recipient at a cost to the actor
• Why does altruism exist in nature?
how can altruistic behaviors evolve?
Br – C > 0

14. The evolution of altruism
• an altruistic act benefits a recipient at a cost to the actor
• Why does altruism exist in nature?
how can altruistic behaviors evolve? Br – C > 0
let B = benefit to recipient

15. The evolution of altruism
• an altruistic act benefits a recipient at a cost to the actor
• Why does altruism exist in nature?
how can altruistic behaviors evolve? Br – C > 0
let B = benefit to recipient
let C = cost to actor
  (Both B and C are measure in units of surviving offspring)

16. The evolution of altruism
• an altruistic act benefits a recipient at a cost to the actor
• Why does altruism exist in nature? Br – C > 0
how can altruistic behaviors evolve?
let B = benefit to recipient
let C = cost to actor
let r = coefficient of relatedness between actor
and recipient

17. The evolution of altruism
• an altruistic act benefits a recipient at a cost to the actor
• Why does altruism exist in nature? Br – C > 0
how can altruistic behaviors evolve?
let B = benefit to recipient
let C = cost to actor
let r = coefficient of relatedness between actor
and recipient
An allele for an altruistic behavior will be favored if:
 Br – C > 0

18. The evolution of altruism
• an altruistic act benefits a recipient at a cost to the actor
• Why does altruism exist in nature?
how can altruistic behaviors evolve? Br – C > 0
let B = benefit to recipient
let C = cost to actor
let r = coefficient of relatedness between actor
and recipient
An allele for an altruistic behavior will be favored if:
Br – C > 0 or Br > C

19. The evolution of altruism
• an altruistic act benefits a recipient at a cost to the actor
• Why does altruism exist in nature?
how can altruistic behaviors evolve? Br – C > 0
let B = benefit to recipient
let C = cost to actor
let r = coefficient of relatedness between actor
and recipient
An allele for an altruistic behavior will be favored if:
Br – C > 0 or Br > C
  • this is called “Hamilton’s rule”

20. Hamilton’s rule and the concept of inclusive fitness  

21. Hamilton’s rule and the concept of inclusive fitness  
• “inclusive fitness” is equivalent to an individual’s total fitness

22. Hamilton’s rule and the concept of inclusive fitness  
• “inclusive fitness” is equivalent to an individual’s total fitness
  Inclusive fitness

23. Hamilton’s rule and the concept of inclusive fitness  
• “inclusive fitness” is equivalent to an individual’s total fitness
  Inclusive fitness 
“Direct” component
(i.e., individual’s own
reproduction)

24. Hamilton’s rule and the concept of inclusive fitness  
• “inclusive fitness” is equivalent to an individual’s total fitness
  Inclusive fitness
 
“Direct” component “Indirect” component
(i.e., individual’s own (i.e., act of individual that
reproduction) increases fitness of its
relatives)

25. Hamilton’s rule and the concept of inclusive fitness  
• “inclusive fitness” is equivalent to an individual’s total fitness
  Inclusive fitness
 
“Direct” component “Indirect” component
(i.e., individual’s own (i.e., act of individual that
reproduction) increases fitness of its
relatives)
kin selection is a form of natural selection favoring the spread of alleles that increases the indirect component of fitness.

26. A deeper look into Hamilton's rule
which is ……..

27. A deeper look into Hamilton's rule
which is ……..
Br > C

28. What is the coefficient of relatedness (r)?

29. What is the coefficient of relatedness?
• r is the probability that homologous alleles present in different individuals are “identical by descent”.   

30. What is the coefficient of relatedness?
• r is the probability that homologous alleles present in different individuals are “identical by descent”.   
• the inbreeding coefficient, F, is the probability that two homologous alleles present in the same individual are identical by descent.

31. What is the coefficient of relatedness?
• r is the probability that homologous alleles present in different individuals are “identical by descent”.   
• the inbreeding coefficient, F, is the probability that two homologous alleles present in the same individual are identical by descent.
• r can be estimated from:

32. What is the coefficient of relatedness?
• r is the probability that homologous alleles present in different individuals are “identical by descent”.   
• the inbreeding coefficient, F, is the probability that two homologous alleles present in the same individual are identical by descent.
• r can be estimated from:
1. pedigrees

33. What is the coefficient of relatedness?
• r is the probability that homologous alleles present in different individuals are “identical by descent”.   
• the inbreeding coefficient, F, is the probability that two homologous alleles present in the same individual are identical by descent.
• r can be estimated from:
1. pedigrees
2. genetic estimates of relatedness

34. Estimating r from pedigrees

35. Estimating r from pedigrees
Parents contribute ½ of their genes….
The prob that genes are IBD in
each step= 1/2
(1/2 * 1/2 )= 1/4

36. Estimating r from pedigrees
(1/2 * 1/2 )+(1/2 * 1/2 )= 1/2

37. Estimating r from pedigrees
(1/2 * 1/2 * 1/2)= 1/8

38. Examples of Kin Selection
Selfish or Altruistic?

39. Alarm calls are given to warn kin
Hoogland 1983

40. Alarm calls are given to warn kin
Hoogland 1983

41. Examples of Kin Selection :
Helping at the nest in bee-eaters

42. Examples of Kin Selection :
Helping at the nest in bee-eaters
Daughter
Daughter/ Helper
Mother
Each parent, unaided, is able to raise 0.51 offspring…………
Each helper is responsible for an additional 0.47 offspring being raised!

43. Helping at the nest in bee-eaters, why?
Mother-Daughter
Actor
1/2
Recipient
Sister
Sister
r = 1/2

44. Bee-eaters direct help to close relatives
Emlen et al. 1995
*relatedness matters!

45. Helping at the nest in bee-eaters, why?
Hamilton’s rule

46. Helping at the nest in bee-eaters, why?
Hamilton’s rule
Breeding Conditions
nest sites difficult to obtain, create and maintain
finding a mate is difficult
scarcity of food
defense of nests

47. Helping at the nest in bee-eaters, why?
Hamilton’s rule (Genetic predisposition)
Breeding Conditions (Ecological Constraint)

48. Helping at the nest in bee-eaters, why?
Hamilton’s rule
Breeding Conditions
First time breeders pay a slight cost:

49. Helping at the nest in bee-eaters, why?
Hamilton’s rule
Breeding Conditions
First time breeders pay a slight cost
-Each parent, unaided, is able to raise 0.51 offspring
-Each helper is responsible for an additional 0.47
offspring being raised!

50. The evolution of eusociality

51. The evolution of eusociality
• in eusocial species some individuals forego reproduction to aid in the rearing of others.

52. The evolution of eusociality
• in eusocial species some individuals forego reproduction to aid in the rearing of others.
• most common in the Hymenoptera (ants, bees, and wasps)

53. The evolution of eusociality
• in eusocial species some individuals forego reproduction to aid in the rearing of others.
• most common in the Hymenoptera (ants, bees, and wasps)
Three characteristics of eusociality:

54. The evolution of eusociality
• in eusocial species some individuals forego reproduction to aid in the rearing of others.
• most common in the Hymenoptera (ants, bees, and wasps)
Three characteristics of eusociality:
1. overlapping generations of parents and their offspring

55. The evolution of eusociality
• in eusocial species some individuals forego reproduction to aid in the rearing of others.
• most common in the Hymenoptera (ants, bees, and wasps)
Three characteristics of eusociality:
1. overlapping generations of parents and their offspring
2. cooperative brood care

56. The evolution of eusociality
• in eusocial species some individuals forego reproduction to aid in the rearing of others.
• most common in the Hymenoptera (ants, bees, and wasps)
Three characteristics of eusociality:
1. overlapping generations of parents and their offspring
2. cooperative brood care
3. specialized castes of non-reproductive workers.

57. Why should eusociality be so common in the Hymenoptera?  
Worker Drone Queen
Reproductive
Sterile

58. Why should eusociality be so common in the Hymenoptera?
• Hamilton suggested it is was due to haplodiploidy:

59. Why should eusociality be so common in the Hymenoptera?
• Hamilton suggested it is was due to haplodiploidy:
• females develop from fertilized eggs (diploid)
• males develop from unfertilized eggs (haploid)

60. Haplodiploidy skews relatedness

61. Comparison Diploid Haplodiploid
Degree of relatedness (r)
Comparison Diploid Haplodiploid

62. Comparison Diploid Haplodiploid
Degree of relatedness (r)
Comparison Diploid Haplodiploid
sister – sister ½ ¾

63. /2 1
Sister

64. /2 1 Sister r = (1/2*1/2) + (1/2*1) = 3/4
Half of a female’s genes come from the father; the probability that a copy of one of these is shared by with the sister is 1.
r = (1/2*1/2) + (1/2*1) = 3/4

65. Comparison Diploid Haplodiploid
Degree of relatedness (r)
Comparison Diploid Haplodiploid
sister – sister ½ ¾
mother – daughter ½ ½

66. Daughter

67. Comparison Diploid Haplodiploid
Degree of relatedness (r)
Comparison Diploid Haplodiploid
sister – sister ½ ¾
mother – daughter ½ ½
sister – brother ½ ¼

68. r = 1/4

69. Comparison Diploid Haplodiploid
Degree of relatedness (r)
Comparison Diploid Haplodiploid
sister – sister ½ ¾
mother – daughter ½ ½
sister – brother ½ ¼
• the inclusive fitness of female workers is highest if they help produce more sisters!
Create= Queen–Worker conflict, who wins?

70. Does haplodiploidy explain the evolution of eusociality?

71. Does haplodiploidy explain the evolution of eusociality?
NO!

72. Does haplodiploidy explain the evolution of eusociality?
NO!
1. Many colonies in eusocial species are founded by more than one queen.  

73. Does haplodiploidy explain the evolution of eusociality?
NO!
1. Many colonies in eusocial species are founded by more than one queen.
• workers in these colonies have r = 0.

74. Does haplodiploidy explain the evolution of eusociality?
NO!
1. Many colonies in eusocial species are founded by more than one queen.
• workers in these colonies can have r = 0.
2. Many eusocial colonies have more than one father.

75. Does haplodiploidy explain the evolution of eusociality?
NO!
1. Many colonies in eusocial species are founded by more than one queen.
• workers in these colonies can have r = 0.
2. Many eusocial colonies have more than one father.
• the average r among workers is far below ¾.

76. Does haplodiploidy explain the evolution of eusociality?
NO!
3. Many eusocial species are not haplodiploid and not all haplodiploids are eusocial.
Examples: termites (diploid) are eusocial

77. Does haplodiploidy explain the evolution of eusociality?
NO!
1. Many eusocial species are not haplodiploid and not all haplodiploids are eusocial.

78. A phylogeny of the hymenoptera

79. their young ones for extended periods.
A phylogeny of the hymenoptera
Eusociality evolved in groups that build complex nests and that care for
their young ones for extended periods.

80. A eusocial mammal – the naked mole-rat

82. Naked mole-rat queens maintain control by bullying
Sherman 1991

83. Factors contributing to evolution of eusociality
Nesting behaviors: complex nests with prolonged care for
young ones
Inbreeding: leads to very high relatedness coefficient (r)
Group defense against predation
Severely constrained breeding opportunities
NOT haplodiploidy!

84. The evolution of reciprocal altruism
Bob Trivers

85. The evolution of reciprocal altruism
• this form of altruism may occur among unrelated individuals.

86. The evolution of reciprocal altruism
• this form of altruism may occur among unrelated individuals.
Trivers suggested that two conditions must be met:

87. The evolution of reciprocal altruism
• this form of altruism may occur among unrelated individuals.
Trivers suggested that two conditions must be met:
Cost must be ≤ to the benefit received.
Cost low, benefit high

88. The evolution of reciprocal altruism
• this form of altruism may occur among unrelated individuals.
Trivers suggested that two conditions must be met:
1. Cost must be ≤ to the benefit received.
• otherwise they will not be favored by selection

89. The evolution of reciprocal altruism
• this form of altruism may occur among unrelated individuals.
Trivers suggested that two conditions must be met:
1. Cost must be ≤ to the benefit received.
• otherwise they will not be favored by selection
2. Individuals that fail to reciprocate must be punished.

90. The evolution of reciprocal altruism
• this form of altruism may occur among unrelated individuals.
Trivers suggested that two conditions must be met:
1. Cost must be ≤ to the benefit received.
• otherwise they will not be favored by selection
2. Individuals that fail to reciprocate must be punished.
• otherwise cheaters can invade the population.

91. Trivers proposed that three factors might facilitate reciprocal alturism:

92. Trivers proposed that three factors might facilitate reciprocal alturism:
1. Groups are stable

93. Trivers proposed that three factors might facilitate reciprocal alturism:
1. Groups are stable
2. Opportunities for altruism are numerous

94. Trivers proposed that three factors might facilitate reciprocal alturism:
1. Groups are stable
2. Opportunities for altruism are numerous
3. Altruists interact in symmetrical situations

95. Blood-sharing in vampire bats

96. Blood-sharing in vampire bats

97. Blood-sharing in vampire bats
Displaying both reciprocal altruism and kin selection
Wilkinson 1984