11-09-11 Reciprocal Altruism and Sex and Sexual Selection

11-09-11 Reciprocal Altruism and Sex and Sexual Selection -...

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ZOL 445 Evolution November 9 , 2011 Reciprocal Altruism and Sex and Sexual Selection Reciprocal Altruism Altruism evolves and is resistant to subversion when there’s a high probability that both donor and recipient share the allele for altruism. o Occurs if recipient/donor are KIN. Br > C r = the probability that donor and recipient share the same allele by descent. o Occurs if recipient/donor recognize each other as altruists Greenbeard Effect But what about altruism between unrelated individuals? o Cleaner fish and Eel: Cleaner fish that eat parasites out of eel’s mouth; benefit: eating. Eel benefit: parasite removal But why doesn’t the eel eat the cleaner fish after it’s done? NOT eating is a form of altruism Eating the fish would elevate the fitness of the eel, and so the behavior would spread and eliminate the cleaning symbiosis. o Vampire Bats: Prey is rare: 33% of young bats do not feed on a given night. Not eating for 3 nights in a row leads to death. Therefore, 3.7% of bats should die every night. Except… …bats regurgitate blood meals to kin and unrelated individuals! Reciprocal altruism and cooperation: Trivers (1971) proposed reciprocal altruism was a mechanism for the evolution of cooperative behaviors. Conditions for reciprocal altruism to evolve: 1. Behavior must reduce the fitness of the donor relative to the selfish individual – it must be “altruistic”. 2. The fitness of the recipient must increase 3. The performance of the behavior must not depend on the receipt of an immediate benefit 4. There must be repeated interactions between the same set of individuals
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This note was uploaded on 12/21/2011 for the course BIO 202 taught by Professor Brooks during the Fall '11 term at UCSB.

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11-09-11 Reciprocal Altruism and Sex and Sexual Selection -...

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