Catastrophe-dispersion models in random and varying environments across generations

TL;DR

This paper introduces a unified framework for analyzing branching processes with varying and random environments, focusing on survival thresholds across different dispersal mechanisms.

Contribution

It develops a universal approach to determine survival or extinction in complex, environment-dependent branching processes with explicit thresholds for certain growth models.

Findings

Survival and extinction depend solely on the log-mean process.

Four dispersal mechanisms are analyzed with a universal offspring mean ordering.

Explicit extinction thresholds are derived for Poissonian growth with binomial survival.

Abstract

We study a class of branching processes in which the offspring distribution is not specified directly but is induced by a cycle of internal colony growth, catastrophic reduction and structured dispersal. The parameters governing growth, survival and dispersal are allowed to vary deterministically or randomly from one generation to the next, giving rise to branching processes in varying and random environments with implicitly defined offspring laws. We show that survival and extinction are governed entirely by the associated log-mean process, exactly as in the classical theory. The paper treats four qualitatively different dispersal mechanisms and establishes a universal ordering of the induced offspring means. For Poissonian growth with binomial survival, explicit thresholds are obtained that determine extinction or survival uniformly over all four mechanisms. A series of ecologically motivated examples with Yule-Simon growth illustrates the versatility of the framework.