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Inclusive Fitness Vivian Hubby Game Theory • How can alternative reproductive strategies exist? • Game theory evaluates alternative strategies where the outcome depends not only on each individual’s strategy, but also on the strategies of other individuals. Game Theory With Side-Blotched Lizards • Most aggressive • Large territories with many females Game Theory with Side-Blotched Lizards •Also territorial •Defend smaller territories with fewer females Game Theory With Side-Blotched Lizards •Nonterritorial •Mimic females and use “sneaky” tactics to obtain matings. Game Theory With Side-Blotched Lizards • The relative mating success of each male type is not fixed but changes with the relative abundance of the other male types in the populations. Beats Beats Beats Altruism • Altruism, or selflessness, occurs when animals behave in ways that reduce their individual fitness but increase the fitness of other individuals. Why Altruism? • When parents sacrifice their own personal wellbring to produce and aid offspring, they increase their own fitness by maximizing their genetic representation in the population. • Inclusive fitness is the total effect an individual has on proliferating its genes by producing its own offspring and by providing aid that enables other close relatives, who share many of those genes, to produce offspring. Hamilton’s Rule • B = benefit to the recipient, or the average number of extra offspring that the beneficiary of an altruistic act produces • C = cost to the altruist, or how many fewer offspring the altruist produces • r = coefficient of relatedness, or the probability that if two individuals share a common parent or ancestor, a particular gene present in one individual will also be present in the second individual • rB > C Applying Hamilton’s Rule • B = 2.0 children • C = 5% chance of drowning x 2 children = 0.1 • r = 0.5 • (0.5)(2.0) > (0.1) • 1 > 0.1 Kin Selection • Natural selection that favors altruistic behavior by enhancing reproductive success of relatives is kin selection. • These genes for altruism will be passed on as well. Kin Selection in Nature • Female Belding’s ground squirrels settle near their site of birth. • Almost all alarm calls are given by females, and if a female’s close relatives are dead, she rarely gives alarm calls. Reciprocal Altruism • Reciprocal altruism is behavior characterized by an individual aiding a non-relative that will return the favor in the future. • How can this evolve if many individuals will cheat? • Tit-for-tat: Individuals are always altruistic on the first encounter and will continue to be that way until they are cheated on. They will then retaliate but will return to altruistic behavior when the other individual becomes cooperative. Social Learning • Social learning: learning through observing others • Culture: a system of information transfer through social learning or teaching that influences the behavior of individuals in a population Social Learning of Alarm Calls • Vervet monkeys have distinct alarm calls when they see leopards, eagles, and snakes. • Infant vervets make many mistakes in their calls. • They improve their accuracy with age. They learn how to give the right call by observing other members of the group and receiving social confirmation. Mate Choice Copying • Mate choice copying is a behavior in which individuals in a population mimic the mate choice of others. • Females usually choose the more orange males. • If they see another female choose a less orange male, they will choose it over the more orange male. • A female that mates with males that are attractive to other females may increase the probability that her male offspring will also be attractive and have high reproductive success.