Multi-type logistic branching processes with selection: frequency process and genealogy for large carrying capacities

TL;DR

This paper models multi-species populations with logistic branching processes, analyzing genealogy and frequency dynamics as carrying capacity becomes very large, revealing insights into the ancestral structure under selection.

Contribution

It introduces a new model combining logistic branching processes with mutation and selection, and analyzes the genealogy and frequency process in the large carrying capacity limit.

Findings

Genealogy approximated by a coupling with independent branching processes.

Convergence of lineage counting process to the dual of the limiting diffusion.

Construction of the Ancestral Selection Graph for the model.

Abstract

We present a model for growth in a multi-species population. We consider two types evolving as a logistic branching process with mutation, where one of the types has a selective advantage, and are interested in the regime in which the carrying capacity of the system goes to $\infty$. We first study the genealogy of the population up until it almost reaches carrying capacity through a coupling with an independent branching process. We then focus on the phase in which the population has reached carrying capacity. After recovering a Gillespie--Wright--Fisher SDE in the infinite carrying capacity limit, we construct the Ancestral Selection Graph and show the convergence of the lineage counting process to the moment dual of the limiting diffusion.