4/25/12. Mutualism. Mutualism. Dominance Hierarchy. Mutualism. Selfish Behavior Spiteful Behavior

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1 4/25/12 Dominance Hierarchy Shared gain of direct fitness Example: Prey capture by lion pride Despo0c (a.k.a. steep) Linear (a.k.a. shallow or egalitarian) Alpha Beta Gamma Helping Behavior Delayed gain of direct fitness (dependent upon repayment) Example: Vampire bat blood exchanges Faculta0ve altruism Macaques Wolves Obligate altruism Permanent loss of direct fitness (with potenlal for indirect fitness gain) Example: Honey bee workers foraging for colony Temporary loss of direct fitness (with potenlal for indirect fitness gain followed by personal reproduclon) Example: Florida scrub jay helping at the nest, then gaining parental territory The direct reproductive success of individuals that engage in different kinds of social interactions Effect on direct reproductive success of Type of interaction Social Donor Social Recipient (delayed) Altruism Selfish Behavior Spiteful Behavior - Show Planet Earth : Great Plains Lions (35:45 43:33) or (You Tube) African Wild Dogs (You Tube) 1

2 4/25/12 The Prisoners Dilemma The Prisoners Dilemma Say Player 1 DEFECTS (does not cooperate with their partner) and Player 2 COOPERATES (cooperates with their partner), Player 1 gets 5 points (no prison Lme) and Player 2 gets 0 points (5 years of prison Lme). Say Player 1 and Player 2 both COOPERATE (with each other), then each gets 3 points (2 years of prison Lme). Say Player 1 and Player 2 both DEFECT (each rat out the other), the each gets 1 point (4 years of prison Lme). Dilbert & The Prisoner s Dilemma Marc Hauser Faculta0ve Altruism Show Trials of Life: Friends & Rivals Baboons (You Tube) Vampire Bats (Raw Nature & You Tube) Show Trials of Life: Growing Up Scrub Jays 2

3 4/25/12 Faculta0ve Altruism Show Nature Living Together Social Behavior Kin SelecLon Brown Babblers Faculta0ve Altruism Obligate Altruism (a.k.a. Eusocial Behavior) Show Nature Living Together Social Behavior Kin SelecLon Naked Mole Rats Snapping Shrimp (You Tube) Eusocial Animals 3 Main Traits for Eusocial Animals Other traits... 3

4 4/25/1 Kin Selec0on Eusocial Animals Coefficient of Relatedness (r) r =.5 n Show Nature Living Together Social Behavior & Kin SelecLon Bees & Hamilton Worker Honeybees the ul0mate in eusocial behavior William D. Hamilton Haplodiploid reproduc0on Hymenoptera Coefficient of relatedness: What propor0on of genes are shared by two individuals? SIMPLE! Find the number of conneclons between one individual back to a shared ancestor and then the number of conneclons to the second individual. RAISE 1/to the power of the number of conneclons. DO THIS separately for EACH shared ancestor and then add the probabililes together. FOR EXAMPLE: # for half sibs there are two conneclons [and only one shared ancestor] so raise 1/to the power of two [1/squared = 1/4; 25% related) # for full sibs each has two conneclons [BUT they share TWO ancestors: mom ANdad] so raise 1/to the power of two for mom and then again for dad [1/squared = 1/4, then again; the two ancestors result in 1/41/4 = 1/2: 50% related] # for first cousins each has FOUR conneclons so raise 1/to the power of FOUR4 (=1/16); then again = 1/16; added together = 1/8 4

5 4/25/1 Half Sibling Coefficient of Relatedness B # for half sibs there are two conneclons [and only one shared ancestor] so raise 1/to the power of two [1/squared = 1/4; 25% related) A B Full Sibling Coefficient of Relatedness # for full sibs each has two conneclons [BUT they share TWO ancestors: mom ANdad] so raise 1/ to the power of two for mom and then again for dad [1/squared = 1/4, then again; the two ancestors result in 1/41/4 = 1/2: 50% related] r = r between & = 0.25 r = r between & = 0.5 Cousin Coefficient of Relatedness # for first cousins each has FOUR conneclons so raise 1/to the power of FOUR4 (=1/16); then again = 1/16; added together = 1/8 Haplodiploid reproduc0on Hymenoptera E F r = r between & = Haplodiploid Coefficient of Relatedness of Sisters Since drones have only one set of chromosomes they must all be shared by the sisters! So now the equalon changes! There is a 100% chance the sisters share their fathers genes not just a 50% chance like that in diploid species! Haplodiploid Coefficient of Relatedness of Daughters & Drone dad r = r between & = 0.75 r = 1 r between & A = 5

6 4/25/1 Haplodiploid Coefficient of Relatedness of Daughters & Queen (mom) Haplodiploid Coefficient of Relatedness of Brothers & Sisters r = 0.5 r between & A = 0.5 r = 0.5 r between & = 0.25 Is haplodiploidy necessary to be eusocial? Is haplodiploidy sufficient to be eusocial? 6