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Moran models and Wright–Fisher diffusions with selection and mutation in a one-sided random environment

Published online by Cambridge University Press:  09 March 2023

Fernando Cordero*
Affiliation:
Bielefeld University
Grégoire Véchambre*
Affiliation:
Academy of Mathematics and Systems Science, Chinese Academy of Sciences
*
*Postal address: Faculty of Technology, Bielefeld University, Box 100131, 33501 Bielefeld, Germany. Email address: fcordero@techfak.uni-bielefeld.de
**Postal address: Academy of Mathematics and Systems Science, Chinese Academy of Sciences, No. 55, Zhongguancun East Road, Haidian District, Beijing, China. Email address: vechambre@amss.ac.cn

Abstract

Consider a two-type Moran population of size N with selection and mutation, where the selective advantage of the fit individuals is amplified at extreme environmental conditions. Assume selection and mutation are weak with respect to N, and extreme environmental conditions rarely occur. We show that, as $N\to\infty$, the type frequency process with time sped up by N converges to the solution to a Wright–Fisher-type SDE with a jump term modeling the effect of the environment. We use an extension of the ancestral selection graph (ASG) to describe the genealogical picture of the model. Next, we show that the type frequency process and the line-counting process of a pruned version of the ASG satisfy a moment duality. This relation yields a characterization of the asymptotic type distribution. We characterize the ancestral type distribution using an alternative pruning of the ASG. Most of our results are stated in annealed and quenched form.

Information

Type
Original Article
Copyright
© The Author(s), 2023. Published by Cambridge University Press on behalf of Applied Probability Trust

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