Lecture 5 - Sociality

Question 1

What are the four main types of social behaviour?

Answer 1

Mutualism
Selfish
Altruism
Spite (Harms both)

Question 2

Why does kin selection work?

Answer 2

Most important means of cooperation
r = P(relatives sharing copy of same gene by descent)
Evolution doesn’t distinguishbetween copies from offspring vs sibing’s offspring

Question 3

What are the types of fitness?

Answer 3

Direct fitness - fitness via personal reproduction
Indirect fitness - Fitness due to aiding relatives
Inclusive fitness = direct + indirect fitness

Question 4

What is Hamilton’s rule?

Answer 4

Conditions under which an altruistic act will spread by kin selection
(B/C) > (1/r) or rB - C > 0

B = benefit to recipient
C = cost to donor
r = relatedness

Question 5

How does competition influence altruism?

Answer 5

Competition between relatives may reduce altruism spread
Must be considered
For cooperative/altruistic behaviour to evolve:

(rxyb) - C - (rxed) > 0

rxy = relatedness between donor and recipient
rxe = relatedness between donor and individuals who differ due to competition from donor
d = reduction in fitness due to altruistic act

Question 6

Do animals treat their kin differently? Provide examples

Answer 6

Yes
Beldings ground squirrels more likely to produce a costly alarm call in presence of close relatives (Sherman, 1977)
Fewer tiger salamander cannibals in kin groups
Cannibalism occurs later in kin groups
In mixed litters of mice, young gain more weight proportionally (Hager and Johnstone, 2005)

Question 7

How do animals recognize relatives?

Answer 7

Shared environment so familiarity eg. birdsong
Only teaches who SHOULD be a relative
Self-referent matching - graded response to strangers based on comparison of phenotype and of self and relatives
Green beard effect - identify those with same distinctive genetic marker

Question 8

What cristicisms have there been of kin selection?

Answer 8

Its a mathematical construct
Pairwise and additive interactions assumed which ingores impacts of multiple interactions
Only describes static interactions - dynamic populations need constant updating
No empirical tests
Only works for small subset of species when standard natural selection works for all

Question 9

How have people responded to criticisms of inclusicve fitnes theory?

Answer 9

Incorrect distinction between natural selection and inclusive fitness
Natural selection explains appearance, inclusive fitness explains why
Only full sibling families evolved eusociality, so r is important
Hamilton: individual fitness isn’t maximised, inclusive fitness is
If benefit high enough, altruism will evolve

Question 10

What is direct reciprocity?

Answer 10

Cooperation between individuals
C < B and reciprocation from recipient in future meeting
Cheats are a problem
Evolutionarily stable reciprocity depends on the uncertainty of repeated interactions

Question 11

How do you win prisoner’s dilemma?

Answer 11

Tit for tat
Cooperate on first move
Do what opponent did on previous move
ESS if W is large enough

Question 12

What is an ESS?

Answer 12

E(I,I) > E(J,I)

I = stable strategy
J = possible mutant
E = evolution

Question 13

How does tit for tat evolve?

Answer 13

All defect are also ESS
Kin selected cooperation can create clusters in which tit for tat can enjoy benefits of mutual cooperation
Cooperation based on reciprocity can evolve if individuals can retaliate W high
Donors must be able to recognize cheaters and refuse to aid
Must be high probability for a given individual to be a donor or recipent
Vampire bats

Question 14

What is indirect reciprocity?

Answer 14

Interactions often inbetween individuals who won’t meet again
Image scoring: if you help others to increase their reputation they may be more likely to help you
Bystanders gain benefits from this
eg. cleaner fish

Question 15

How does spite evolve?

Answer 15

rB - C > 0

Requires negative relatedness
Costly action to unrelated individual may benefit related individual
Found where kin and non kin interact in competitive environments
eg. bacteria

Question 16

Describe spite in the parasitoid wasp

Answer 16

Lay one male and one female egg into moth eggs
Each produces 1000s of larvae asexually
Some females become sterile soldiers and kill less related brothers
Find relatedness with extraembryonic membrane to discover who is related

Question 17

Summarise West et al, 2007`

Answer 17

If assistance gives greater benefits, more kin discrimination
Haplodiploid hypothsesis is false so cooperation in Hymenoptera due to high cost to benefit ratio
Punsishment can favour cooperative behaviour
Need more integration between empirical and theory

Question 18

Summarise Nowark et al 2010

Answer 18

Inclusive fitness theory requires assumptions that aren’t required by natural selection and are unrealistic in a real system
Inclusive fitness says cooperative behaviour is a result of relatedness, but authors believe it is the other way around eg. nest and food

Question 19

Summarise Abbot et al, 2011

Answer 19

Response to Nowark et al, 2010
Assumptions are not required for inclusive fitness, general as natural selection, just for specific species
Biological progress has been made with inclusive fitness theory eg. explaining gender ratios

Question 20

Summarise Wilson and Wilson, 2007

Answer 20

A trait which disadvantages total fitness of an individual but benefits the group will evolve, therefore group selection must be ~real~
Group selection is not always ineffective across generations eg. when predators introduced
Group selection abandoned based on theory only, while some empirical evidence suggests it might be a thing
All evolutionary behaviour models share key points
Altruistic traits are detrimental to individual.so must be group selection (ever heard of inclusive fitness pal????)