Interactions and migration rescuing ecological diversity

TL;DR

This paper uncovers a new mechanism by which ecological diversity is maintained through interactions and migration, revealing how ecosystems can resist extinction despite demographic fluctuations, with implications for predicting catastrophic shifts.

Contribution

It introduces a novel understanding of how heterogeneity, migration, and demographic noise collectively sustain diversity in ecosystems, extending previous models.

Findings

Diversity can be preserved via a balance of interactions and migration.

Ecosystems exhibit bistability and tipping points influenced by demographic noise.

A method to predict catastrophic shifts in ecological diversity is proposed.

Abstract

How diversity is maintained in natural ecosystems is a long-standing question in Theoretical Ecology. By studying a system that combines ecological dynamics, heterogeneous interactions and spatial structure, we uncover a new mechanism for the survival of diversity-rich ecosystems in the presence of demographic fluctuations. For a single species, one finds a continuous phase transition between an extinction and a survival state, that falls into the universality class of Directed Percolation. Here we show that the case of many species with heterogeneous interactions is different and richer. By merging theory and simulations, we demonstrate that with sufficiently strong demographic noise, the system exhibits behavior akin to the single-species case, undergoing a continuous transition. Conversely, at low demographic noise, we observe unique features indicative of the ecosystem's complexity. The combined effects of the heterogeneity in the interaction network and migration enable the community to thrive, even in situations where demographic noise would lead to the extinction of isolated species. The emergence of mutualism induces the development of global bistability, accompanied by sudden tipping points. We present a way to predict the catastrophic shift from high diversity to extinction by probing responses to perturbations as an early warning signal.