Inclusive Fitness

1
Inclusive Fitness

• Psychology 3107

2
Introduction

• Darwin was troubled by the preponderance of
  behaviour that seemed to be of no benefit to the
  actor
• Examples
• Sterile insect castes
• Bee stings
• Alarm calling
• Reproductive restraint

3
Reproductive restraint

• Birds can produce many more eggs than they
  actually do!
• Wynne-Edwards beleied that selection also acted
  on the species level to stop massive
  overpopulation

4
Reproductive Restraint?

• Lack argued that animals are doing what is best
  for the INDIVIDUAL
• Big clutch means possible exhaustion, death
• LIFETIME fitness, not just this season

5
Lack

• Well, if clutch size depends on the environment,
  then clutch size should vary with quality of
  resources

6
Hamilton figured it out

• Hamiltons Response was theoretical
• Look at behaviour from the genes point of view
• Inclusive fitness direct fitness effect on
  fitness of others

7
Hamilton

• C lt rb
• Or r gt c / b
• Remember, r is relatedness, c is cost b is
  benefit
• Would you give your life for a brother?
• No, but maybe 2 brothers, or 8 cousins
• Two uncles and one mother.

8
Mechanism

• For this to work there must be some sort of
  proximate mechanism
• Easy for mother/father and child
• How about everyone else?
• Green Beard hypothesis
• Allele produces some phenotype
• Also allows for recognition
• Tough for a single gene.

9
The elusive mechanism

• Proximity
• Families
• Little dispersal
• So if close by, you are related
• Example
• Leaf eating ants
• Far nests ? more hostile
• Different plants ? more hostile

10
More on mechanism

• Those crazy ants
• Split colony and put on different plants
• Hostile, but non injurious!
• Gene environment interaction baby!
• Vervet monkeys
• 2 year olds scream
• Mother comes
• Others watch the mother!

11
Mechanisms, pheremones and bees

• Greenberg looked at bee relatedness and allowing
  bees in or not
• Probably genetically determined odour

12
Conclusions

• Group selection is silly
• Individual selection is cool
• Gene level selection is VERY cool
• Hamilton is a genius
• Dont over use this
• Gives us some insight into some nasty human
  behaviour