+. reciprocal altruism: one organism provides a benefit to another in the expectation of future...
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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