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Biology and game theory Where are we now and how did we come here? A biologist’s perspective Olof Leimar, Department of Zoology, Stockholm University The Logic of Animal Conflict Maynard Smith & Price (1973) Mule deer males fighting Arabian oryx males fighting “reducing intra-specific damage” Julian Huxley (1966). Ritualization of behaviour in animals and man. The logic of asymmetric contests Maynard Smith & Parker (1976) Papilio zelicaon male Hilltopping P. zelicaon male “The resident always wins” Davies (1978). Territorial defence in the speckled wood butterfly (Pararge aegeria) Typical habitat for speckled wood butterflies Does the resident always win? Does the resident always win? The role of motivation Bergman, Olofsson & Wiklund (2010) Contest outcome in a territorial butterfly Christer Wiklund Polymorphism and morph determination Papilio dardanus Papilio dardanus Papilio dardanus model mimic model mimic model mimic Batesian mimicry Polymorphism The Dobzhansky - Cain & Sheppard - Fisher polymorphism debate Dobzhansky (1951) Genetics and the origin of species Genetic polymorphism as such is frequently adaptive Theo. Dobzhansky Cain & Sheppard (1954) The theory of adaptive polymorphism "This interesting theory may be correct, but it is not clear what is meant by one population being more highly adapted than another to a particular environment" Arthur Cain A precursor of the group selection debate Fisher concluded the debate Fisher (1958) Polymorphism and natural selection "I would not have alluded to this storm in a tea-cup, but for the circumstance that I mean to put forward some ideas on this problem of the possible adaptive value of polymorphisms" Dobzhansky is right, but the idea traces back to "a little-known book of nearly a hundred years ago, called The Origin of Species" "one way of making this intelligible is by the analogy of games of skill, or to speak somewhat more pretentiously, of the Theory of Games" Fisher regarded polymorphism as an adaptive strategy The “Darwin joke” Phenotype determination Schwander & Leimar (unpubl.) Phenotype determination Schwander & Leimar (unpubl.) Sex determination Bulmer & Bull (1982). Models of polygenic sex determination and sex ratio control Ouachita map turtle Baby Sex determination Van Dooren & Leimar (2003). The evolution of environmental and genetic sex determination in fluctuating environments. Mechanisms of sex determination Central bearded dragon lizard Quinn et al. (2007). Temperature sex reversal implies sex gene dosage in a reptile. Climate-driven population divergence in sex-determining systems Pen et al. (2007) Snow skink Five rules for the evolution of cooperation Nowak (2006) From a biologist’s perspective some things are missing • Biological markets • Sanctions and partner choice • By-product benefits • Pseudoreciprocity • Common interest Leimar & Hammerstein (2010). Cooperation for direct fitness benefits. Sanctions in legume rhizobium mutualism Bacteria fix atmospheric nitrogen inside root nodules of leguminous plants What if the bacteria do not fix nitrogen? Experiments suggest that the plant then re-allocates its resources (Kiers et al. 2003) Recent work claims that the role of sanctions is small (Marco et al. 2009) Comment Sanctions are best understood as a by-product of an action that is of direct interest to the actor Cleaning mutualism: by-product benefits There are immediate benefits (food and removal of ectoparasites) for the partners Ant-lycaenid mutualism: pseudoreciprocity Lycaenid larvae invest in sweet secretion – ants forage and protect their food resource Mycorrhizae: exchange of organic carbon and mineral nutrients between plants and fungi Could it work like human trading and exchange? Mutual investments in by-product benefits Leimar & Connor (2003) Bever et al (2009) Evolution of common interest Contributing factors • Cost of changing partners, resulting in partner fidelity • Increased dependence on partners Acacia plant housing mutualistic ants Extrafloral nectar is offered The extrafloral nectar • contains glucose and fructose • is virtually void of sucrose Ants of the genus Pseudomyrmex • have lost the capacity to digest sucrose • depend on this nectar (Kautz et al. 2009) Possible evolution of increased dependence as a by-product of the advantage of being less attractive to non-mutualistic ants