Evolutionary Analysis 4/e

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Kin Selection and Social Behavior
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I. Motivation

• Cooperative behaviors are widespread.
• Why?

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Genetically related female banded mongooses live
and breed in groups, and care for each other's
young
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, -
Actor
Recipient
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II. Theory of Altruism

• An individuals survivorship and reproduction
  relative to other individuals in the population
  (Direct Fitness)
• Hamiltons Rule (1964)
• Inclusive fitness
• Direct fitness indirect fitness
• Kin selection natural selection favoring the
  indirect component of fitness
• (Benefit x relatedness) Cost gt 0 Br gt C r gt
  C/B
• Benefit to recipient and cost to altruist
• Relatedness probability that homolgous alleles
  in 2 individuals are identical by descent

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Indirect Fitness through a Relative
Computing relatedness with pedigrees
The arrows describe paths by which genes can be
identical by descent
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III. Evidence
Black-tailed prairie dogs give more alarm calls
when kin are nearby
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Male black-tailed prairie dogs change their alarm
calling behavior when their living situation
changes
5 males
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Helping Behavior in Birds White-fronted
bee-eaters
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In bee-eaters, helpers assist close relatives
Fitness gains due to helping
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Kin-selected discrimination in cannibalistic
tadpoles and salamanders
Benefit
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IV. Special case of Sociality True or
Eusociality 1. overlap in
generations between parents and offspring
2. cooperative brood care 3.
specialized castes of nonreproductive individuals
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Haplodiploidy produces unusual coefficients of
relationship
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Haplo-diploidy and Sister-Sister relationship
Sisters on average share ½ genes through
mother all of their genes through father (1/2
1)/2 ¾ Or ¼ ½ 3/4
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phylogeny of the hymenoptera
Origins of complex nesting behaviour
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In paper wasps, the success of female coalitions
varies
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Naked mole-rats have highly inbred colonies
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Naked mole-rat queens preferentially shove
nonrelatives
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V. Siblicide and Parent-Offspring Conflict
Masked boobies
Blue-footed boobies
Older sib sometimes pushes sib from nest
Older sib always pushes sib from nest
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VI. Reciprocal Altruism
Vampire bats This photo shows a group of vampire
bats roosting in a hollow tree
Cooperative behavior among non kin
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Also fed nest mates that had fed them
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Conclusion

• Cooperative behaviors are widespread
• Inclusive fitness
• (B x r) C gt 0
• Haplo-diploidy
• Siblicide
• Reciprocal altruism (Tit for Tat)
• Other interesting topics P-O conflict, sex ratio
  evolution, greenbeard alleles

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VII. Parent-offspring conflict
Weaning conflict
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Parent-offspring conflict results from changes in
the costs and benefits of parental care and
asymmetries in relationship
Full Sib
half-sib
Parent should stop investing below 1, and
offspring will stop harrassing parent at ½, or ¼,
respectively
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Bee-eaters recruit helpers who are younger and
closely related