Random walk in genome space : A key ingredient of intermittent dynamics of community assembly on evolutionary time scales

TL;DR

This paper investigates community assembly dynamics in evolutionary models, revealing that mutation-driven processes lead to intermittent, $1/f$-like fluctuations, while migration-driven processes produce smooth, random-walk-like diversity changes, highlighting universal macroevolutionary patterns.

Contribution

It demonstrates the distinct effects of mutation and migration on community assembly dynamics and identifies universal species-lifetime distributions in macroevolution.

Findings

Mutation models show $1/f$ diversity fluctuations.

Migration models exhibit $1/f^2$ random-walk fluctuations.

Species-lifetime distribution follows a power law with a long tail.

Abstract

Community assembly is studied using individual-based multispecies models. The models have stochastic population dynamics with mutation, migration, and extinction of species. Mutants appear as a result of mutation of the resident species, while migrants have no correlation with the resident species. It is found that the dynamics of community assembly with mutations are quite different from the case with migrations. In contrast to mutation models, which show intermittent dynamics of quasi-steady states interrupted by sudden reorganizations of the community, migration models show smooth and gradual renewal of the community. As a consequence, instead of the $1/f$ diversity fluctuations found for the mutation models, $1/f^2$, random-walk like fluctuations are observed for the migration models. In addition, a characteristic species-lifetime distribution is found: a power law that is cut off by a "skewed" distribution in the long-lifetime regime. The latter has a longer tail than a simple exponential function, which indicates an age-dependent species-mortality function. Since this characteristic profile has been observed, both in fossil data and in several other mathematical models, we conclude that it is a universal feature of macroevolution.