Lecture 16: Selfish Genes

Question 1

Altruistic behaviour:

Answer 1

When one individual performs & action for the benefit of another. e.g. parent caring for offspring, alarm calls in birds, social behaviour
-important in understanding evolution of behaviour

Question 2

e.g. of Altruistic behaviour:

Answer 2

Belding’s ground squirrels:

• Give alarm calls when a predator approaches: an altruistic action
• Sherman & colleagues studied the evolution of alarm calls in groups
• The likelihood of an individual giving an alarm call was related to whether the group contains relatives or not.
• Tested empirically by putting individuals into different groups

Question 3

An altruistic action will be favoured if it

Answer 3

benefits kin

Question 4

altruistic behaviours evolve if –>

Answer 4

rb > c
r is relatedness of target individual
b is benefit to target
c is cost to giver

Question 5

cousins relatedness

Answer 5

0.125

Question 6

what is kin selection?

Answer 6

actually is ‘gene selection’

-kin selection measures the effects of selection at the level of individual genes

Question 7

r X b > c

Answer 7

• r is probability that a member of kin contains a gene for an altruistic act
• b is number of extra copies of the gene the act yields
• c is cost to giver in terms of lost number of copies of the gene that individual produces

Question 8

a gene will spears in a population if it

Answer 8

causes more copies of itself to be produced.

-Kin selection is the most obvious example, but itsnt strictly the only mechanism = SELFISH GENES

Question 9

why called selfish genes?

Answer 9

• Anything that a gene can do to favour its own spread at the expense of others will be favoured by selection
• Altruism is only favoured by evolution if it increases the rate of spread of a gene
• Hence the term selfish
• The individual doesn’t play any role in this
• It is just the outcome for the gene that is important

Question 10

on what does selection act?

Answer 10

ultimately on genes.

-genes are contained within individuals.

Question 11

Green Beard Genes

Answer 11

-does not require relatedness

Question 12

Green beards vs Kin recognition:

Answer 12

-UNRELATED INDIVIDUALS: Green beard: genes for action and signal are linked, but individuals are unrelated at other loci
-RELATED INDIVIDUALS
Genetic kin recognition: genes for action and signal are linked, but individuals are related at all loci

Question 13

Green Beard examples:

Answer 13

• important because whet demonstrate the PRINCIPLE of gene level selection
• RED FIRE ANTS
• all e.g. laying queens are Bb
• bb queens die naturally
• BB queens are killed by Bb workers
• Use odours to distinguish between BB &Bb
• Genotype linkes to behaviour hence a green beard effect

Question 14

Blue beards in lizards:

Answer 14

• Unrelated male lizards form partnerships to protect territories
• These have blue throats
• Under some circumstances one of the males may have no offspring = ‘true altruism’
• Genes for throat colour and cooperation are linked
• Hence a true green-beard effect

Question 15

Kin selection or GB more common?

Answer 15

• probably Kin
• But Green Beard effect is a logical consequence of gene-level selection
• These are important because they demonstrate the principle of gene level selection
• Relatively few examples
• ‘false-beards’ can easily ‘cheat’
• Cheating: possess the green beard but do not reciprocate altruism
• Green beards are probably evolutionarily unstable

Question 16

whats more important gene-selection or individual selection?

Answer 16

gene-selection.

Gene-selection affects evolution of genetic material, within genome competition e.g. meiotic drive

Question 17

tazmanian devil face tumour:

Answer 17

• A disease spread from animal to animal, quickly fatal
• Spreads in the form of individual cells
• Cells are not of host genotype
• But are unrecognised by immune system
• They are essentially another individual, derived from another geontype
• This genotype is actually threatening the existence of the species

Question 18

what does selection act on?

Answer 18

REPLICATORS

• these are individual units that replicas themselves
• those that leave most copies are the most successful

Question 19

what are replicators??

Answer 19

GENES ARE

species are not & are therefore not the units of selection. NOR are individuals

Question 20

cooperation / non-cooperation

Answer 20

• Evolutionarily stable strategies
• Individuals cooperate for their own selfish reasons
• If a gene codes for a cooperative behaviour it will only be favoured if this causes it to spread faster

Question 21

example of cooperation:

Answer 21

-cleaner fish cleaning the mouth of a client. The client fish could very easily snap its mouth shut and eat the cleaner – but it doesn’t because it gets a benefit from being cleaned. And the cleaner only does it because it gets a meal.
-Cleaner-client interaction advantageous for both parties
However cheating sometimes occurs
Client may eat the cleaner
Cleaner may parasitize the client

Question 22

when is cooperation favoured?

Answer 22

• is favoured only when it increases the fitness of the individual concerned
• The level of cooperation (or not) is a balance of positive and negative fitness effects of cooperation
• Cooperation only evolves when it benefits the individuals interacting
• i.e. is not altruistic, but is selfish

Question 23

Kin selection explain

Answer 23

the evolution of altruism

Question 24

Kin selection is

Answer 24

gene selection

Question 25

Gene selection predicts

Answer 25

green beard effects