Lecture 20: Levels of selection

Question 1

Wynne-Edwards

Answer 1

‘Old’ group selection

• reproductive self-restraint to avoid over exploitation of resources
• conditions for old group selection are unlikely to be met in nature
• selfish gene likely to spread

Question 2

‘old’ group selection demolished by

Answer 2

George Williams and Richard Dawkins ‘the selfish gene’

Question 3

how can old group selection work?

Answer 3

if groups die out faster than others, but individuals die quicker than groups, so individual selection will be more powerful

• groups must be isolated so selfish individuals can’t move between them
• groups w just coop, they do better than just selfish, groups w both selfish will override over generations BUT VERY UNLIKELY TO OCCUR IN NATURE

Question 4

‘New’ group selection: who and how does it differ

Answer 4

• EO wilson, david wilson & martin Nowak

- should look at selection as a multilevel process (genes, cels, organisms, group) David wilsons russian doll concept

Question 5

New group selection: explanation =

Answer 5

-populations are divided into ‘trait groups’ or demes
- selection acts for or against traits within groups
-groups mix together before splitting into new groups and the next round of selection
===
- coop groups contribute more to next gen, self biased ones less
- they tend to associate w same trait (C&C, S&S) before forming new group

Question 6

New group selection: cooperative traits will spread when

Answer 6

between group selection is stronger than within group selection

Question 7

cooperation is favoured by:

Answer 7

• increasing group benefits
• reducing individual cost
• reducing within-group genetic variance, relative to between-group genetic variance (when regroup they regroup w same, C&C)
• • relate to hamilton rule

Question 8

new group selection models are mathematically equivalent to

Answer 8

hamilton rule for the evolution of altruism; rB>c

Question 9

if new group selection models and inclusive fitness theory are mathematically equivalent, are they also as useful?

Answer 9

NO.

• inclusive fitness theory tells us that quantity which is maximised by natural selection under all conditions
• • new group selection model is restrictive, not same generality

Question 10

empirical study:to show group selection

Answer 10

social spider:

• colony extinction is frequent
• limited dispersal
• colonies have a mix of docile & aggressive phenotypes, site specific (affect success of colony)
• artificial colonies of mixes of docile / aggressive phenotypes at diff sites
• 2 gen monitored
• mix gens change to match original mixture
• suggest group trait is locally adapted

-criticised tho, not down to individual selection? Much scepticism

Question 11

conditions for group selection to operate are extremely __ in nature

Answer 11

limited