An analytically tractable model for community ecology with many species

TL;DR

This paper introduces a simple, analytically solvable presence-absence model for community ecology that captures key dynamics of species assembly, diversity, and competition, aligning with complex models and neutral theory.

Contribution

It presents a novel, tractable presence-absence model that reproduces qualitative features of complex community assembly models and highlights ecological phase transitions.

Findings

Model reproduces features of complex community models

Identifies ecological phase transitions near a critical point

Aligns with Hubbell's neutral theory of biodiversity

Abstract

A fundamental problem in community ecology is to understand how ecological processes such as selection, drift, and immigration give rise to observed patterns in species composition and diversity. Here, we present a simple, analytically tractable, presence-absence (PA) model for community assembly and use it to ask how ecological traits such as the strength of competition, the amount of diversity, and demographic and environmental stochasticity affect species composition in a community. In the PA model, species are treated as stochastic binary variables that can either be present or absent in a community: species can immigrate into the community from a regional species pool and can go extinct due to competition and stochasticity. Despite its simplicity, the PA model reproduces the qualitative features of more complicated models of community assembly. In agreement with recent work on large, competitive Lotka-Volterra systems, the PA model exhibits distinct ecological behaviors organized around a special ("critical") point corresponding to Hubbell's neutral theory of biodiversity. These results suggest that the concepts of ecological "phases" and phase diagrams can provide a powerful framework for thinking about community ecology and that the PA model captures the essential ecological dynamics of community assembly.