McElreath, R., & Solis, J. (2001). Can females gain extra paternal investment by mating with multiple males? A game theoretic approach. American Naturalist, 158, Can Females Gain Extra Paternal Investment by Mating with Multiple Males? A Game Theoretic Approach Alexandra Alanzo, Alana Pontrelli, & Palmer Thornton

McElreath, R., & Solis, J. (2001). Can females gain extra paternal investment by mating with multiple males? A game theoretic approach. American Naturalist, 158, Benefits from multiple mating by females zInsuring insemination zAvoiding genetic incompatibility zPromoting sperm competition zProducing genetically different offspring zAvoiding infanticide zAcquiring courtship food zAcquiring additional paternal investment from males

McElreath, R., & Solis, J. (2001). Can females gain extra paternal investment by mating with multiple males? A game theoretic approach. American Naturalist, 158, What is game theory? zStudies strategic interaction and competition in competitive and cooperative environments zIn this particular study: the success of both male and female strategies depend on the strategies that other individuals use

McElreath, R., & Solis, J. (2001). Can females gain extra paternal investment by mating with multiple males? A game theoretic approach. American Naturalist, 158, Model 1: The evolution of Male Investment zExamines the conditions in which males invest in offspring of their mates rather than seek other mating opportunities zPaternal investment Vs. mating investment z2 Strategies y“dads”: mate with females and invest in the offspring of their mates instead of seeking other mates y“cads”: never invest in offspring and instead use their time and energy to acquire other mates

McElreath, R., & Solis, J. (2001). Can females gain extra paternal investment by mating with multiple males? A game theoretic approach. American Naturalist, 158, Model 2: Polyandry and Paternal Investment zExamines the payoffs for females to invest in multiple males assuming that males already invest in offspring zPolyandry rare: polyandrous females acquires half of the investment from all monogamous females in the social group zPolyandry common: investment is shared with all the females in the group, but costs of mating with many different males must be paid z2 Main Strategies ymonogamous females mate with one male in the group, each female mates with a different male ypolyandrous females mate with all males in the group

McElreath, R., & Solis, J. (2001). Can females gain extra paternal investment by mating with multiple males? A game theoretic approach. American Naturalist, 158, Discussion zModel 1 yMales seek additional mating rather than invest in offspring under many different situations yWhen the value of male care is abundant and future mating opportunities are limited, then investing males are favored yWhen the social groups are small then male investing in multiple females is favored

McElreath, R., & Solis, J. (2001). Can females gain extra paternal investment by mating with multiple males? A game theoretic approach. American Naturalist, 158, Discussion cont’d zModel 2 zMating with multiple males for paternal investment can explain a small amount of polyandry but this is only true when the benefit of male investment is at least 10 times the cost of mating zMating with multiple males become costly because the females must share paternal investment zDiminishing returns to male investment

McElreath, R., & Solis, J. (2001). Can females gain extra paternal investment by mating with multiple males? A game theoretic approach. American Naturalist, 158, Critical Review zModel 2 assumes that paternal investment will occur and that males will divide their resources equally among the females. zModel 1 shows males controlling mating while Model 2 shows females controlling mating, but what is both sexes wanted to control mating strategies? Conflict between the sexes would occur. zWhat if certain males can identify females’ fertile periods? This would defeat the purpose of polyandry since females would not receive extra investment from males.