Altruism: Voluntary or Coerced? Altruism Requires Decrease Actor’s Direct Fitness Increase Recipient’s Direct Fitness Social Insects Eusociality  Sterile Worker Caste Workers Altruists Kin Selection & Inclusive Fitness?

Eusocial Altruism Economics of Inclusive Fitness Must Apply: Evolution by Natural Selection Altruism Voluntary or Altruism Socially Coerced?

Coercion Punishment or “Policing” of Group Members Inhibits Selfishness Punishment: Deters Recipient’s Future Selfishness Aggression Policing: Deters Recipient’s Current Selfishness Queen, Workers Aggression to Inhibit Ovarian Function Eat Worker-Laid Eggs

Ratnieks & Wenseleers (2007) TREE 23:45. Inclusive Fitness Calculations: Compare Voluntary vs Coerced Altruism Variety of Behaviors, Variation in Relatedness Argue for Significance of Coercion

Ratnieks & Wenseleers (2007) TREE 23:45. Coercion, by Queen or Other Workers Promotes Worker Altruism Reduces Benefit of Direct Worker Reproduction, Relative to Benefit of Rearing Kin Workers Comply with Group Norm Maintains Caste Altruism Assert: Cooperation Can be Enforced

Ratnieks & Wenseleers (2007)TREE 23:45. Examples: Social Insects, Social Vertebrates Plant

Ratnieks & Wenseleers (2007) TREE 23:45. Honeybees Queen Mates with 1 – 10 Males Worker Related to Sister: 0.75  r  0.3 Relatedness May Be Too Low for Voluntary Altruism of Hamilton’s Rule Worker Can Be More Closely Related to Own Offspring Than to Queen’s Offspring

Ratnieks & Wenseleers (2007) TREE 23:45. Honeybees Altruism Persists Workers Kill/Police Eggs Laid by Other Workers Deters Current Worker Reproduction Benefit of Rearing Kin May Be Greater

Ratnieks & Wenseleers (2007) TREE 23:45. If Too Many Workers Laid Eggs: Overwhelm Remaining Workers Colony Would “Die” All Individuals: No Inclusive Fitness May Favor Coercion to Enforce Altruism

Ratnieks & Wenseleers (2007) TREE 23:45. Eusocial Form: 20 – 40  10 6 Years Old, Across Insecta Some Cases: Kin-Selected, Voluntary Altruism Other Cases: Coerced Altruism