Predicting The First Steps Of Evolution In Randomly Assembled Communities

By Keith Cowing
Status Report
February 12, 2024
Filed under , , ,
Predicting The First Steps Of Evolution In Randomly Assembled Communities
Modeling the first steps of evolution in a randomly assembled community that competes for substitutable resources. (A) Microbial strains compete for R resources that are continuously supplied by the environment at rates κi . Each strain µ has a characteristic set of uptake rates rµ,i (arrows), which can be altered by further mutations. (B) A local pool of S initial species, whose phenotypes are randomly drawn from a common statistical distribution, self-assembles into an ecological equilibrium with S ∗ ≤ S surviving species (left). A new mutation (M) arises in one of the surviving species (P); if the mutation provides a fitness benefit, its descendants can either replace the parent strain (top right) or stably coexist with the parent, potentially driving another species to extinction (bottom right). —

Microbial communities can self-assemble into highly diverse states with predictable statistical properties. However, these initial states can be disrupted by rapid evolution of the resident strains. When a new mutation arises, it competes for resources with its parent strain and with the other species in the community.

This interplay between ecology and evolution is difficult to capture with existing community assembly theory. Here, we introduce a mathematical framework for predicting the first steps of evolution in randomly assembled communities that compete for substitutable resources.

We show how the fitness effects of new mutations and the probability that they coexist with their parent depends on the size of the community, the saturation of its niches, and the metabolic overlap between its members.

We find that successful mutations are often able to coexist with their parent strains, even in saturated communities with low niche availability. At the same time, these invading mutants often cause extinctions of metabolically distant species.

Our results suggest that even small amounts of evolution can produce distinct genetic signatures in natural microbial communities.

John McEnany, Benjamin H. Good

Predicting the First Steps of Evolution in Randomly Assembled Communities


Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻