Classical Kin Selection

Kin Selection

Kin Selection  Natural Selection Fitness: Lifetime Reproductive Success Inclusive Fitness Direct & Indirect Components W.D. Hamilton, 1964

Helpers at the Nest: Feed Siblings

Inclusive Fitness Diploid Genetics Gene for Altruism

Inclusive Fitness Indirect Fitness Component of Behavior: Net Changes to Relatives’ Fitness, Devalued by Coefficient of Relatedness r, Caused by Selfs Behavior Does Not Include Fitness Relatives Enjoy Outside of Interaction with Self

Inclusive Fitness Hamilton’s Rule for Kin Altruism B Net Benefit of Act on Relatives’ Fitness C Fitness Cost to Self Natural Selection Favors Act r B – C > 0

Inclusive Fitness Social Insects Equivalent Version Hamilton’s Rule Gene for Kin Altruism: Care for Relative’s Offspring Assume Sterile Worker Has Altruism Allele Favored by Natural Selection?

Haplo-Diploidy Males: Haploid (N) Females: Diploid (2N) Relatedness

Inclusive Fitness Gene for Kin Altruism: Care for Relative’s Offspring B: Rear Extra b Offspring of Relative; r 1 Self’s Relatedness to Offspring C: Lose c of Self’s Offspring; r 2 Self’s Relatedness to Offspring

Inclusive Fitness Kin Altruism: Care for Relative’s Offspring r 1 B – r 2 C > 0 B, C Units of females

Inclusive Fitness Haplodiploid Eusociality Worker Caste: All Females Queen = Mother to Self Egg/Larva = Sister to Self “Worker’s Daughter” = Cost C

Inclusive Fitness Haplodiploid Eusociality Self’s (Worker’s) Relatedness to “Daughter” Self’s (Worker’s) Relatedness to “Daughter” Females Diploid, Have Father & Mother r 2 = ½ Since Daughter Would Also Have Father Cost C for Daughter = r 2 Cost C for Daughter = r 2 = 1/2

Inclusive Fitness Haplodiploid Eusociality Self’s (Worker’s) Relatedness to Sister, Daughter Self’s Mother & Father Self’s (Worker’s) Relatedness to Sister, Daughter Self’s Mother & Father r 1 : Altruism Gene, Identical by Descent, Through Father (Haploid) or Mother = Queen (Diploid)

Inclusive Fitness Haplodiploid Eusociality r 1 = ½ [1] + ½ [1/2] = ¾ > ½ = r 2 Father: No Meiosis; Mother: 1 Meiosis Self More Closely Related to Sister than to Her Own “Daughter”

Inclusive Fitness Haplodiploid Eusociality Reproductive Altruism Favored: r 1 B – r 2 C > 0 Let c = 1 female (daughter); (3/4)b – (1/2) > 0 b > 2/3; Reproductive Altruism Favored Via Kin Selection

Inclusive Fitness Haplodiploid Eusociality b > 2/3; Reproductive Altruism Favored Via Kin Selection If worker can raise 2 sisters instead of raising 3 daughters, benefit of altruism = cost of altruism

Inclusive Fitness Haplodiploid Eusociality Drones: Males Queen = Mother to Son Egg/Larva = Brother to Ego “Worker’s Son” = Cost c

Inclusive Fitness Haplodiploid Eusociality Assume Worker Has Altruistic Allele Self/Worker: Has Father Drone: No Father r 1 = Pr[Allele From Mother]/2 = (1/2) (1/2) 1 = 1/4

Inclusive Fitness Haplodiploid Eusociality Worker Less Closely Related to Brother Than To (Hypothetical) Son Brother Than To (Hypothetical) Son More Workers Than Drones Workers Raise Drones

(Haplodiploid) Eusociality Kin Selection: Focus on Within-Nest Social Behavior Nests Differ in Productivity = Rate of Forming New Colonies Focus on Between-Nest Competition Family Level Group Selection?

(Haplodiploid) Eusociality Does Queen Manipulate Sisters (Workers) to Raise Her Offspring? Mechanism vs Function Current Areas of Research

Kin Selection Facultative Sociality Individuals “Decide” to Breed Alone or Help Relative Altruistically Carpenter Bee Xylocopa sulcatipes Nest: Hollow Plant Stems, Excavate Cavity in Wood

Kin Selection Females Nest Singly or in Pairs Pair: Mother & Daughter, Dominant and Subordinate Mother: Reproductive Consumes Any Eggs of Daughter Most Foraging, Provision Brood

Kin Selection Mother & Daughter, Dominant and Subordinate Daughter: Helper, No Reproduction Guards Nest/Brood Nest Lost, New Occupant Kills Brood

Why Daughter Altruistic? Cost: Offspring as Solitary, 1.5 Benefit: Extra Offspring Produced by Mother-Daughter Pair Pair: 5.5 Offspring Extra Offspring = 5.5 – 1.5 = 4 Weigh Cost & Benefit by Relatedness

Why Daughter Altruistic? Altruist’s Guarding Reduces Chance of Losing Brood Allows Dominant More Time to Forage & Provision Brood Facultative Sociality: Economic Basis in Kin Selection

Classical Kin Selection “Inclusive Fitness Thinking” Eusociality Evolution of Family Parent-Offspring Conflict