On the structure pf genealogical trees in the presence of selection

TL;DR

This study uses simulations to explore how selection influences genealogical tree structures and nucleotide variation statistics in asexual populations, revealing a mutation rate-dependent threshold effect in large populations.

Contribution

It provides new insights into the impact of selection and epistasis on genealogical tree structure and nucleotide diversity in asexual populations through numerical simulations.

Findings

Selection affects genealogical tree shape and nucleotide variation.

A threshold phenomenon emerges at large population sizes depending on mutation rate.

Diminishing epistasis attenuates deleterious mutation effects.

Abstract

We investigate through numerical simulations the effect of selection on two summary statistics for nucleotide variation in a sample of two genes from a population of N asexually reproducing haploid individuals. One is the mean time since two individuals had their most recent common ancestor ($\bar{T_s}$), and the other is the mean number of nucleotide differences between two genes in the sample ($\bar{d_s}$). In the case of diminishing epistasis, in which the deleterious effect of a new mutation is attenuated, we find that the scale of $\bar{d_s}$ with the population size depends on the mutation rate, leading then to the onset of a sharp threshold phenomenon as N becomes large.