On the scope of applicability of the models of Darwinian dynamics

TL;DR

This paper critically examines the applicability of Vincent and Brown's evolutionary dynamics model, demonstrating that it is only accurate for linearly dependent population dynamics and highlighting its limitations with non-linear cases.

Contribution

The paper clarifies the limitations of Vincent & Brown's approach, showing it is only exact under linear population dynamics and providing examples where it fails.

Findings

The approach is exact only for linear trait dependence.

Non-linear dynamics can lead to incorrect results.

The scope of the model's applicability is more limited than previously claimed.

Abstract

In their well-known textbook (Vincent & Brown, 2005), Vincent and Brown suggested an attractive approach for studying evolutionary dynamics of populations that are heterogeneous with respect to some strategy that affects the fitness of individuals in the population. The authors developed a theory, whose goal was to expand the applicability of mathematical models of population dynamics by including dynamics of an evolving heritable phenotype trait subject to natural selection. The authors studied both the case of evolution of individual traits and of mean traits in the population (or species) and the dynamics of total population size. The authors consider the developed approach as (more or less) universally applicable to models with any fitness function and any initial distribution of strategies, which is symmetric and has small variance. Here it was shown that the scope of the approach proposed by Vincent & Brown is unfortunately much more limited. I show that the approach gives exact results only if the population dynamics linearly depends on the trait; examples where the approach is incorrect are given.