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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 survivalr = 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 cousinsN=3; r=0.25Indirect fitness = 3x0.25=0.75

N = the number of traits/individuals of a relatedness classr = 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 gainedFinally, 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 mates2. 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