Lecture 15

Lecture 15 - - - - - Inclusive fitness o The sum of an...

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- Inclusive fitness o The sum of an individual’s direct and indirect fitness W i = a i + Ʃ (r ij b ij ) W i : inclusive fitness of i a i : individual direct fitness of i r ij : coefficient of relatedness between i and j b ij : benefit to j from the help of i Ʃ (r ij b ij ) = indirect fitness of i if it helps j - Hamilton’s rule: an altruistic gene will increase in frequency if it follows the rule: o Help when b x r > c Benefit to recipient multiplies by the coefficient of relatedness > cost to donor Should I jump into a river to save 8 drowning cousins or 2 drowning brothers? r(brother) = 0.5 2(0.5) = 1 r(cousin) = 0.125 8(0.125) = 1 Doesn’t matter - Some sample questions? o Is it better to help your sister raise five daughters or to have two daughters yourself? o You have a choice between saving your half-sister, and your cousin. Thinking of only inclusive fitness, which would you save? o You have the option of helping your mother raise your 2 brothers or your step-father raise your three half-sisters. Which yields the highest benefit to you? - Hamilton’s rule o Altruistic behaviors are most likely to spread when costs are low, benefits to recipient are high, and the participants are closely related o A Case Study: Helping behavior in White-fronted bee-eaters (Emlen) Helping behavior in birds: kin selection? Offspring that are old enough to breed on their own instead help their parents rear siblings Occurs in species where nest sites or other resources are extremely limited (about 10% of bird species) In some species, fledging success is <50%, even with helpers HYP: If cooperative breeders follow Hamilton’s rule, then helpers should assist closely related individuals more than others Nest in colonies (~200 individuals per colony) Related individuals defend territories together as ‘clans’ They are cooperative breeders in that ~50% of first year offspring assist in raising other birds’ young rather than having their own young Emlen showed that first year bee-eaters choose who to help based on their coefficient of relatedness! o In other words, they tend to help their close rather than distant relatives
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Eusociality: Extreme Kin Selection? - Ants, bees, and wasps - General characteristics o Live in groups of closely related individuals, usually in a nest or hive o Parents live with offspring and members of the group work together to raise them o There is typically a division of labor in that large numbers of individuals are sterile (e.g. workers, soldiers) whereas relatively few are reproductive (queens, drones) o The queen or queens typically lays all the eggs
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This note was uploaded on 06/21/2011 for the course NPB 102 taught by Professor Hahn during the Spring '09 term at UC Davis.

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Lecture 15 - - - - - Inclusive fitness o The sum of an...

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