Lecture 16: Selfish Genes Flashcards
Altruistic behaviour:
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
e.g. of Altruistic behaviour:
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
An altruistic action will be favoured if it
benefits kin
altruistic behaviours evolve if –>
rb > c
r is relatedness of target individual
b is benefit to target
c is cost to giver
cousins relatedness
0.125
what is kin selection?
actually is ‘gene selection’
-kin selection measures the effects of selection at the level of individual genes
r X b > c
- 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
a gene will spears in a population if it
causes more copies of itself to be produced.
-Kin selection is the most obvious example, but itsnt strictly the only mechanism = SELFISH GENES
why called selfish genes?
- 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
on what does selection act?
ultimately on genes.
-genes are contained within individuals.
Green Beard Genes
-does not require relatedness
Green beards vs Kin recognition:
-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
Green Beard examples:
- 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
Blue beards in lizards:
- 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
Kin selection or GB more common?
- 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
whats more important gene-selection or individual selection?
gene-selection.
Gene-selection affects evolution of genetic material, within genome competition e.g. meiotic drive
tazmanian devil face tumour:
- 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
what does selection act on?
REPLICATORS
- these are individual units that replicas themselves
- those that leave most copies are the most successful
what are replicators??
GENES ARE
species are not & are therefore not the units of selection. NOR are individuals
cooperation / non-cooperation
- 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
example of cooperation:
-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
when is cooperation favoured?
- 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
Kin selection explain
the evolution of altruism
Kin selection is
gene selection
