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Kin Selection and Social Behavior

Cooperative behaviors among social animals highlight the importance of kin selection in evolution. Genetic relatedness drives individuals, like female banded mongooses and black-tailed prairie dogs, to help care for each other's offspring, enhancing their inclusive fitness. The theory of altruism reveals how indirect fitness impacts survival rates. Complex social structures, such as eusociality in hymenoptera, demonstrate the evolutionary advantages of cooperation. Examining instances of reciprocal altruism in species like vampire bats further illustrates the dynamics of social behavior and parental investment conflicts in animal societies.

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Kin Selection and Social Behavior

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  1. Kin Selection and Social Behavior

  2. I. Motivation Cooperative behaviors are widespread. Why?

  3. Genetically related female banded mongooses live and breed in groups, and care for each other's young

  4. +, - Actor Recipient

  5. II. Theory of Altruism An individual’s survivorship and reproduction relative to other individuals in the population (Direct Fitness) Hamilton’s Rule (1964): Inclusive fitness = Direct fitness + indirect fitness Kin selection: natural selection favoring the indirect component of fitness (Benefit x relatedness) – Cost > 0; Br > C; r > C/B Benefit to recipient and cost to altruist Relatedness: probability that homolgous alleles in 2 individuals are identical by descent

  6. Indirect Fitness through a Relative Computing relatedness with pedigrees The arrows describe paths by which genes can be identical by descent

  7. III. Evidence Black-tailed prairie dogs give more alarm calls when kin are nearby

  8. Male black-tailed prairie dogs change their alarm calling behavior when their living situation changes 5 males

  9. Helping Behavior in Birds: White-fronted bee-eaters

  10. In bee-eaters, helpers assist close relatives Fitness gains due to helping

  11. Kin-selected discrimination in cannibalistic tadpoles and salamanders Benefit

  12. 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

  13. Haplodiploidy produces unusual coefficients of relationship

  14. father mother r = ½ ½ 1 1 sister sister 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

  15. phylogeny of the hymenoptera Origins of complex nesting behaviour

  16. In paper wasps, the success of female coalitions varies

  17. Naked mole-rats have highly inbred colonies

  18. Naked mole-rat queens preferentially shove nonrelatives

  19. 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

  20. VI. Reciprocal Altruism Vampire bats This photo shows a group of vampire bats roosting in a hollow tree Cooperative behavior among non kin

  21. Also fed nest mates that had fed them

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

  23. VII. Parent-offspring conflict Weaning conflict

  24. 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

  25. Bee-eaters recruit helpers who are younger and closely related

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