Transcript The concept of adaptive phenotypic polymorphism in evolutionary

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