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Increasing another individual ’ s fitness (b) at a cost (c) to one ’ s own (direct) fitness. Can only work if p (A meets A) > p (NA meets A) (in other words, if care is more likely to be directed to individuals with A). Altruism:. Pay-off to altruist (A):. Pay-off to non-altruist (NA):.

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slide1

Increasing another individual’s fitness (b) at a cost (c) to one’s own (direct) fitness.

Can only work if p (A meets A) > p (NA meets A)

(in other words, if care is more likely to be directed to individuals with A)

Altruism:

Pay-off to altruist (A):

Pay-off to non-altruist (NA):

b (if A meets another A)

- c

b(if NA meets an A)

Having A must be predictive of the recipient having A, too

1. A’s interact repeatedly (reciprocity)

2. A’s occur in groups (group selection)

3. A’s are related (kin selection)

slide2

Hamilton\'sRule

r b - c > 0

r b > c

b 1

--- > ---

c r

r = coefficient of relatedness

(how well donor’s genotype predicts recipient’s genotype)

b = benefit of altruism to recipient

(offspring produced that would not be otherwise)

c = cost of altruism to altruist

(offspring not produced because it helped)

slide3

The coefficient of relatedness (r)

1. Parent and offspring

Parents

D

B

R

DR (.5)1

r = 0.5

slide4

2. Full siblings

Parents

A

B

D

R

DAR (.5)2

slide5

2. Full siblings

Parents

A

B

D

R

DAR (.5)2

DBR + (.5)2

r = .5

slide6

3. Half siblings

Parent

D

R

DPR (.5)2

r = .25

slide7

4. First cousins

A

B

Grandparents

Parent

Aunt/Uncle

DPAUR (.5)4

D

R

DPBUR + (.5)4

r = .125

How to calculate r for any case:

r = ∑(0.5)L L = number of parent-offspring (generational) links

slide8

selection for traits that increase the survival of close relatives, including offspring and non-descendant kin.

Kin selection:

direct fitness

-> fitness gained by increased survival of offspring

because of the individual’s actions

indirect fitness

-> fitness gained by increased survival of non-descendant

kin because of the individual’s actions

direct fitness + indirect fitness = inclusive fitness

slide10

Kin Recognition

a) Social learning

Treatments:

- siblings raised together or apart

- nonsiblings raised together or apart

Number of encounters/5min

ground squirrels

Together

Apart

Together

Apart

Siblings

Nonsiblings

Holmes, W.G. and Sherman, P.W. 1982. The ontogeny of kin recognition in two species of ground squirrels. American Zoologist 22: 491-517

slide11

b) Self-referent phenotype matching ("armpit effect")

Rearing:

- male, female, fostered female

Golden hamster

Foster littermate

Unfamiliar sibling

Unfamiliar nonsibling

Mateo, J.M. and Johnston, R.E. 2000. Kin recognition and the "armpit effect": evidence of self-referent phenotype matching. Proc. Roy. Soc. Lond. (B) 267:695-700.

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