A Dynamical Model for the Origin of Anisogamy

TL;DR

This paper presents a mathematical dynamical model showing that competition linked to mean gamete size naturally leads to the evolution of anisogamy from an initially symmetric isogamous state.

Contribution

It introduces a novel dynamical systems model that explains the emergence of anisogamy through competition dynamics, providing a theoretical basis for this evolutionary transition.

Findings

Competition linked to mean gamete size leads to stable anisogamous equilibrium.

Isogamy can naturally evolve into anisogamy under certain competitive conditions.

The model's predictions are supported by numerical simulations.

Abstract

The vast majority of multi-cellular organisms are anisogamous, meaning that male and female sex cells differ in size. It remains an open question how this asymmetric state evolved, presumably from the symmetric isogamous state where all gametes are roughly the same size (drawn from the same distribution). Here, we use tools from the study of nonlinear dynamical systems to develop a simple mathematical model for this phenomenon. Using theoretical analysis and numerical simulation, we demonstrate that competition between individuals that is linked to the mean gamete size will almost inevitably result in a stable anisogamous equilibrium, and thus isogamy may naturally lead to anisogamy.