Migration and bottlenecks in population genetics

Dai Pra Marta, Humboldt Universität zu Berlin

In population genetics most theory and statistical tests have been developed using the classical Wright--Fisher model and the Kingman coalescent. Nevertheless, organisms having a genealogy not well-described by the Kingman coalescent are not rare: For example, populations that exhibit recurrent strong variation in population size, due to limited resources or natural catastrophes. Surviving organisms can repopulate the environment in a relatively short time, causing many individuals to descend from few ancestor. These genealogies are better captured by coalescents with multiple mergers, also called Lambda-coalescents, or with simultaneous multiple mergers, known as Xi-coalescents. In this talk we focus on spatially-structured populations undergoing localized, recurrent bottlenecks, and describe their ancestral lines. We assume that, after every catastrophe, the affected subpopulation regrows according to a logistic branching process with constant immigration from the other locations. Depending on the severity of the bottlenecks, we derive as scaling limits different structured Xi-coalescents featuring simultaneous multiple mergers and migrations. We are then interested in the impact of immigration during a bottleneck phase. We study the limiting proportion of immigrants surviving in the new habitat under different fitness parameters. Based on joint works with: A. Etheridge, J. Kern, J. Koskela, M. Wilke-Berenguer.

Area: CS13 - Diffusion and coalescent processes in population genetics (Martina Favero)

Keywords: coalescent, multiple mergers, bottlenecks, logistic branching process

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