Lecture 7 - The role of kin selection

Question 1

what are the 2 direct fitness benefits of helping with cooperative breeding?

Answer 1

1) current reproduction

2) increased future reproduction

Question 2

how can cooperative breeding help increase future reproduction? (2 answers)

Answer 2

• acquisition of skills/mate/territory

- group augmentation - better survival in larger group (payment of rent) and future help

Question 3

what is an indirect fitness benefit of cooperative breeding and how?

Answer 3

1) increased fitness of relatives
- better productivity
- better survival of breeders

Question 4

how important are indirect or direct benefits in the evolution of helping behaviour?

Answer 4

The relative importance of indirect or direct fitness benefits in the evolution of helping behaviour is still debated

Question 5

How important is kin selection?

Answer 5

Each of the key evolutionary transitions involve cooperation so modern social evolution theory aims to understand each transition using the logic of inclusive fitness theory

Question 6

what came after the orgin of multicellularity?

Answer 6

the origin of social groups

Question 7

what is eusociality?

Answer 7

‘true sociality’, with non-reproductive castes

Question 8

for the origin of social groups what is the hypothesis for why should individuals join together to become mutually dependent?

Answer 8

High relatedness between individuals played key role in transition to sociality

Question 9

what is the monogamy hypothesis?

Answer 9

Strict lifetime monogamy results in individuals who are equally related to offspring and siblings (both r = 0.5). Any small net benefit from raising siblings rather than offspring will favour cooperation and potentially eusociality

Question 10

what are the 2 accompanying predictions with the monogamy hypothesis?

Answer 10

(i) All eusocial spp. passed through a ‘monogamy window’

(ii) Multiple mating may evolve later, following specialization

Question 11

describe the history of eusocial insects

Answer 11

 all eusocial lineages have passed through an ancestral ‘monogamy window’
 some clades exhibit polyandry but workers are already specialized for helping

Question 12

does the monogamy hypothesis apply to other taxa - not just eusocial insects?

Answer 12

• in mammals it was found there was a strong reproductive skew for cooperative males and females
• Opposite for non-cooperative and therefore low relatedness
• similarly in birds a study found promiscuity to be lower in cooperative species

Question 13

what is the hypothesis for the evolution of cooperative breeding in birds?

Answer 13

Cooperative breeding in birds has evolved in kin groups
- when studying taxa cooperation in kind groups is seen much more frequently that cooperation in non-kin groups supporting the idea that kinship is very important in the evolution of cooperation

Question 14

Kin groups predominate among cooperative breeders however what is the exception?

Answer 14

the exceptions are generally cooperative polygamists where all individuals attempt to breed

Question 15

what are the 2 reasons kinship is so important?

Answer 15

1) Inbreeding avoidance… reduces conflict within groups over reproduction
2) Kin-selected helping… often assumed to be important

Question 16

what are the four particular issues of the general assumption that kin selection is important?

Answer 16

1) Confounding effects of territory/individual quality
2) Direct benefits of helping under-estimated
3) Costs of kin competition ignored (next lecture)
4) Evidence for active kin discrimination

Question 17

what is an example of confounding effects of territory/individual quality

Answer 17

kookaburra - productivity increases with group size up until a point

• when you compare productivity of same territories with different number of helpers in different years - same no. female, more male helpers = no benefit
• same no. male, more female helpers - female helpers hinder!

Question 18

give an example of direct benefits of helping under-estimated?

Answer 18

e. g. paternity in fairy wrens
- now using DNA printing we know that 73% of offspring is produced by extra pair paternity - shows helpers aren’t nearly as closely related to each other as once thought

Question 19

give an example of evidence for active kin discrimination

Answer 19

E.g. Bell miners

• as relatedness increases the net visit rates increase
• meta analysis of kin discrimination within species shows significant kin discrimination across studies- - Comparative analysis of helper effort across 37 species - found a significant positive relationship to helper effort variation and kinship variation -
• variation is consistent with Hamilton’s rule

Question 20

summarise evidence for the 4 issues that kin selection is important

Answer 20

(i) Confounding effects of territory/individual quality?
- control for statistically or experimentally
(ii) Direct benefits of helping under-estimated?
- need genetic analyses of relatedness
iii) Costs of kin competition ignored? – see lectures 11 & 12
- many studies of intra-familial conflict
(iv) Evidence for active kin discrimination?
- good evidence

Question 21

How important is kin selection for evolution of cooperative breeding systems in vertebrates?

Answer 21

• Variable importance in some species

- Unimportant in some species

Question 22

is the evidence for kin selection strong or weak?

Answer 22

can summarise the circumstantial evidence for kin selection as being strong (ubiquity of family structures) and the evidence from single species studies as being strong. However, we are still a long way from answering the question of how relatively important are direct and indirect benefits across cooperative species
- More studies are needed to fully understand the role of kin selection