+

Reciprocal altruism: One organism provides a benefit to another in the expectation of future reciprocation Assumes that cheaters can be identified/punished Assumes that the giver incurs a short-term personal cost Assumes that receivers are not preferentially related to givers Meerkats: Reciprocal altruists? If true: meerkats should: Share sentinel duties equally Sentinels should be at greater risk

Prisoners dilemma: Why reciprocal altruism is very rare in nature In survival terms, catching a cheater is low…when your dead! Conditions under which altruistic behavior should could occur: When there is opportunity for repeated opportunities to give/receive by the same unrelated players: tit for tat When players are related

Direct selection: traits producing altruistic acts that directly influences your/offspring personal fitness Indirect selection: traits producing altruistic acts that directly influences fitness of your genetic relatives Kin selection: traits producing altruistic acts directed at both offspring and closely related individuals How altruistic traits could spread in a population N = Scalable: the number of trait/s or individuals of a relatedness class that enhance survival

Belding’s Ground squirrels: Alarm callers are far more likely to be captured than alarm call receivers Females are twice as likely to give alarm calls Belding’s Ground squirrels: Direct + indirect selection = altruism N = Scalable: the number of trait/s or individuals of a relatedness class that enhance survival r = the coefficient of relatedness of those individuals

Who should you risk your life to save? The fitness value of your 1 child: N = 1; r = 0.5 Direct Fitness = 1x0.5= 0.5 The fitness value of your cousins N=3; r=0.25 Indirect fitness = 3x0.25=0.75 N = the number of traits/individuals of a relatedness class r = the coefficient of relatedness of those individuals Remember: you could think of this at the level of individual alleles Hamilton’s Rule: altruism genes will spread only if the loss of direct fitness for the altruist is less than the indirect fitness gained Finally, what about altruistic acts that only have a probability of reducing your direct fitness? What is your inclusive fitness if: You save only 2 cousins? You save all cousins and your child?

Pied Kingfisher Altruism and inclusive fitness in the Pied Kingfisher Four yearling male phenotypes: 1.Those who find mates 2.Those who don’t find a mate but help their parents raise siblings (primary helpers) 3.Those who don’t find a mate but help strangers raise siblings (secondary helpers) 4.Those who don’t find a mate and wait until next year (delayers) Primary helpers work harder

Three strategies with different fitness payouts

Are these strategies conditional? Sechelles Warbler Experiment: inhabit an island with warblers and monitor the development of helping behaviors as a function of increasing density. Normally this species exhibits helping behavior

Helping behavior emerge as a function of saturation of high quality territories

Territory quality also predicts sex of Warbler offspring