Stockholm university

Olof LeimarProfessor Emeritus

About me

My research spans over a broad range, from evolutionary and game-theory modelling to animal behaviour experiments. Areas I have worked in include game theory in biology, reinforcment learning, conflict and cooperation, animal personality variation, developmental plasticity, genetic polymorphism, and mimicry and aposematism. Currently my main interest is to integrate reinforcment learning and other mechanisms into game-theory modelling.


A selection from Stockholm University publication database

  • Ecological Genetic Conflict

    2019. Olof Leimar (et al.). American Naturalist 193 (1), 70-80


    Genetic polymorphism can contribute to local adaptation in heterogeneous habitats, for instance, as a single locus with alleles adapted to different habitats. Phenotypic plasticity can also contribute to trait variation across habitats, through developmental responses to habitat-specific cues. We show that the genetic architecture of genetically polymorphic and plasticity loci may influence the balance between local adaptation and phenotypic plasticity. These effects of genetic architecture are instances of ecological genetic conflict. A reduced effective migration rate for genes tightly linked to a genetic polymorphism provides an explanation for the effects, and they can occur both for a single trait and for a syndrome of coadapted traits. Using individual-based simulations and numerical analysis, we investigate how among-habitat genetic polymorphism and phenotypic plasticity depend on genetic architecture. We also study the evolution of genetic architecture itself, in the form of rates of recombination between genetically polymorphic loci and plasticity loci. Our main result is that for plasticity genes that are unlinked to loci with between-habitat genetic polymorphism, the slope of a reaction norm is steeper in comparison with the slope favored by plasticity genes that are tightly linked to genes for local adaptation.

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  • Biased generalization of salient traits drives the evolution of warning signals

    2018. Gabriella Gamberale-Stille (et al.). Proceedings of the Royal Society of London. Biological Sciences 285 (1877)


    The importance of receiver biases in shaping the evolution of many signalling systems is widely acknowledged. Here, we show that receiver bias can explain which traits evolve to become warning signals. For warning coloration, a generalization bias for a signalling trait can result from predators learning to discriminate unprofitable from profitable prey. However, because the colour patterns of prey are complex traits with multiple components, it is crucial to understand which of the many aspects of prey appearance evolve into signals. We provide experimental evidence that the more salient differences in prey traits give rise to greater generalization bias, corresponding to stronger selection towards trait exaggeration. Our results are based on experiments with domestic chickens as predators in a Skinner-box-like setting, and imply that the difference in appearance between profitable and unprofitable prey that is most rapidly learnt produces the greatest generalization bias. As a consequence, certain salient traits of unprofitable prey are selected towards exaggeration to even higher salience, driving the evolution of warning coloration. This general idea may also help to explain the evolution of many other striking signalling traits found in nature.

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  • Personality remains

    2018. Anna Favati (et al.). Behavioral Ecology 29 (2), 312-320


    Behavioral responses of male fowl did not depend on social rank after 3 weeks in stable groups, but were consistent over time for an individual. Theory suggests that stable social states, for example, stable social hierarchies, may lead to consistent variation in behavior, that is, variation in personality. Our results suggest that variation in personality is not a consequence of variation in social status and that personality is more important than current social position in determining individual behavior in stable groups.Individuals often differ in behavior in a consistent way, that is, they show variation in personality. Understanding the processes explaining the emergence and maintenance of this variation is a current major topic in the field of animal behavioral research. Recent theoretical models predict that differences in various states can generate individual variation in behavior. Previous studies have mainly focused on endogenous states like metabolic rate or energy reserves, but theory also suggests that states based on social interactions could play important roles in shaping personality. We have earlier demonstrated short-term status-dependent variation in behavior in the domestic fowl (Gallus gallus domesticus), but whether such behavioral variation remains also after a longer period of time, is unknown. Therefore, we examine the influence of social status on variation in behavior, using experimental manipulation of social status in pairs of male domestic fowl. We scored males in 3 personality assays (novel arena test, novel object test, and aggression test) before and after 3 weeks in pairs as either dominant or subordinate. We observed individual consistency of behavior despite alteration of social status. We further found no support for social status acting as a state that generates variation in personality over the used time interval: social status had no significant effect on the change in behavioral responses between repeated personality tests. Our results suggest that personality is more important than current social situation for describing individual behavior in stable groups.

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Show all publications by Olof Leimar at Stockholm University