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Research Fellows Directory

Alexander Stewart

Dr Alexander Stewart

Research Fellow


University College London

Research summary

I use mathematical and computational methods to study questions of evolutionary biology and social behaviour. I am especially interested in the relationship between population genetics and social evolution. I work mostly on questions concerning the potential for complex adaptations in evolving systems, the dynamics of repeated social interactions, and the impact of genetic architecture on evolutionary dynamics.

Repeated social interactions: Cooperative interactions are the basic units of social bahaviour. In higher organisms, and especially in humans, such interactions are many and various. But even among the simplest bacteria, basic cooperative interactions can be complicated to evolve and maintain. I study how behavioural strategies, which determine when an organism will engage in cooperation, change over time in a population. I am especially interested in how the evolution of such strategies is altered by access to information such as memory of past interactions, the public reputation of other individuals, the spatial structure of the population and the relatedness between individuals. I aim to quantify and predict how long it takes behavioural norms to become established in a population, and how long a norm will persist once it is established.

Complex adaptations: Evolvability is the ability of an organism or population to produce a new, adaptive phenotype in response to a new selective pressure. The more evolvable an organism is, the more quickly it can adapt to a new environment. I am interested in the evolvability of complex traits - i.e. those that require multi-step adaptations. In particular I am interested in the influence of both an organism’s external environment and its social environment on evolvability. I am also interested in exploring the extent to which genetic architecture is shaped by the need to be evolvable.

Genetic architecture: Natural selection acts at the level of the phenotype. But the mutations which alter the phenotype occur in the genes. Understanding how genetic information is translated into a phenotype (known as the genotype-phenotype map) is a fundamental problem for biology. However it is already obvious that the way genetic mutations are translated into phenotypic changes can place important constraints on the evolutionary dynamics of natural populations - what changes can occur, how fast and in what order. I am interested in exploring these constraints in systems where the genotype-phenotype map is fairly well understood, such as the transcription regulatory networks (TRNs) which determine gene expression. In particular I am interested in how population genetic factors - such as population size, selection strength, mutation rate, ploidy, spatial and social structure - constrain the genetic architecture of TRNs, and how the genetic architecture of TRNs influence the evolvability of social and non-social traits.

Interests and expertise (Subject groups)

Grants awarded

The population genetics of social dilemmas

Scheme: University Research Fellowship

Dates: Oct 2015 - Sep 2020

Value: £484,919.81