L8 Kin selection and Group selection

What is the definition of altruism?

Any act or behaviour which results in an individual increasing the genetic fitness of another at the expense of its own

What is the definition of natural selection?

Any consistent difference in fitness (reproductive success)among phenotypically (genetically) different biological unit within a population

What are the different levels of natural selection?

- Individual (Phenotype)

- Genotype

- Gene

What is kin selection?

the process by which evolution selects for individuals who cooperate with their relatives

• An explanation for caste system of social insects

• Level of selection = gene

What is inclusive fitness?

a measure of fitness based upon a number of the animal's genes that are present in subsequent generations, rather than the number of offspring

- Depend on coefficient of relatedness (probability that the homologous alleles in two individuals are identical by descent)

What is the kin selection - coefficient of relatedness?

r = total(0.5)^L

L = (No. generations)

What is hamiltons rule of kin selection?

rB - C > 0

B=benefit to recipient

C=cost to actor (altruist)

r=coefficient of relatedness

• Inclusive fitness

- Direct fitness

- Indirect fitness

What 2 things does inclusive fitness consist of?

- Direct fitness

- Indirect fitness

What is an example of kin selection?

E.g. cannibalistic tadpoles Ambystoma tigrinum

What is kin selection - Hymenoptera?

• Hymenopteran eusociality

1. Overlap in generations

2. Cooperative brood care

3. Specialised castes of nonreproductive individuals

• Haplodiploidy?

What is haplodiploidy in kin selection?

Calculation of coefficient of relatedness

• Trace all lines of ancestry, including proportion of genes that are Identical By Descent (IBD)

• Sister 1, has half genes identical with Mother

Mother has half genes identical with Sister 2) + (Sister 2 shares half her genes with Father

Father shares all his genes with Sister 1 =(1/2 ½) + (1/2 1) = ¾

What is the modification for species with limited dispersal in kin selection?

• Explains the evolution of altruism

• But high estimates of relatedness is not, in itself, sufficient evidence for the role of kin selection

• Limited dispersal → competition with relatives

• Frank's method b=B-a(B-c)

- B=benefit to recipients if do not compete

- c=cost of altruism to actor

- a= competition, a=0 → global, as a increases, competition is more local

How does kin selection relate to altruism?

• Altruism is prevalent, despite predictions that these "self-sacrificing" behaviours should be selected again

• E.g. assisting in care of siblings, rather than reproducing

• E.g. Sterile castes in hymenoptera

How does kin selection compare to the idea of inclusive fitness?

1. Inclusive fitness theory is more general than kin selection

2• Inclusive fitness theory states that what is necessary is a statistical association of altruistic genotypes

3• Kinship is one way for this to occur

4• Other ways = repeated interactions between non-relatives (e.g. prisoner's dilemma or green beard genes)

5• Therefore, inclusive fitness theory explains a range of social phenomena e.g. reciprocal altruism

What is group selection?

Adaptations that benefit the group

- Individuals follow a common code, demonstrating behaviours for the good of the group

What did Wynne-Edwards state about group selection?

• 1.5: Natural selection operates largely or entirely at 2 levels

- Individuals (intraspecific selection)

- Species (interspecific selection)

• But, some species have dominance hierarchies e.g. social insects "inconceivable in a world where the most successfully fecund were bound to be individually favoured by selection and the infertile condemned to extinction."

• "an intraspecific process...(concerned) with the viability and survival of the stock or the race as a whole"

• "Only possible method of evolving sterile castes"

Was Wynne-Edwards paper controversial?

yes

Does group selection occur?

- Lots of debate over this

Whether kin or group selection is true

- Hamilton stated in his original article that inclusive fitness theory is more general than kin selection

-By 2000s, the term Multilevel selection was being used instead

-explain the evolution of altruism by considering the action of natural selection not on an individual but on a group

How is group selection different from kin selection?

• Group selection ideas use a multi-level approach to partition selection into components of within group and between group selection

• Group selection modules are not fundamentally different from classical kin selection models

What is the core of natural selection? what happens?

Core of natural selection is that when replicators arise and make copies of themselves:

1. Their numbers will tend, under ideal conditions, to exponentially increase

2. They will necessarily compete for finite resources

3. Some will undergo random copying errors

4. Whichever copying errors happen to increase the rate of replication will accumulate in a lineage and predominate in the population

Is the core of natural selection true for group selection?

No, doesn't follow any of the 4 points

What is the false allure of group seletion?

- It doesn't follow the cores of natural selection

- Group selection in innately appealing to us (we are highly adapted to group living) but no evidence for its existence

What is the theory of kin selection?

a type of natural selection that considers the role relatives play when evaluating the genetic fitness of a given individual