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Unformatted text preview: 1/26/10 1 178 178 Levels of selection Traits may beneFt entities at different levels of organization Nevertheless, traits are not expected to evolve “for the good of the species” blue = altruistic, pink = selFsh 179 179 Levels of selection Group selection is only plausible if groups have heritable Ftness variation. But 1) Group heritability is likely to be low- groups often not stable entities because of migration 2) More birth/death of individuals per unit time Individual selection arguments are favored 1/26/10 2 180 180 Nevertheless, we observe apparently altruistic traits Fut 14.15 "I would lay down my life for two brothers or eight cousins”-JBS Haldane Belding’s ground squirrel Pied king¡sher 181 181 An apparently altruistic act is associated with a ¡tness cost to the actor and a ¡tness bene¡t to the recipient. Under certain circumstances, such traits can spread. Hamilton’s rule: apparently altruistic traits may evolve if rb > c r = degree of relatedness between actor and recipient (full sibs, r = 0.5) b = bene¡t to recipient c = cost to actor Inclusive ¡tness Consider a rare allele which results in an act that reduces the ¡tness of the indiv. Consider a rare allele which results in an act that reduces the ¡tness of the indiv....
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- Winter '10
- Evolution, G. C. Williams, Haldane, Belding, Unisexual P. formosa, Unisexual Cnemidophorus