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Altruism:

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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Altruism:

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  1. 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)

  2. 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)

  3. The coefficient of relatedness (r) 1. Parent and offspring Parents D B R DR (.5)1 r = 0.5

  4. 2. Full siblings Parents A B D R DAR (.5)2

  5. 2. Full siblings Parents A B D R DAR (.5)2 DBR + (.5)2 r = .5

  6. 3. Half siblings Parent D R DPR (.5)2 r = .25

  7. 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

  8. 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

  9. 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

  10. 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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