Invasion and Interaction Determine Population Composition in an Open Evolving System

TL;DR

This paper explores how invasion events and species interactions influence population diversity and composition in open evolving ecosystems, revealing two distinct regimes based on invasion frequency and interaction strength.

Contribution

It introduces a dynamic model combining invasion and interaction effects, highlighting how invasion frequency and interaction strength shape community diversity and stability.

Findings

Low diversity with abrupt species dominance shifts when interactions are strong and invasions are slow.

Higher diversity with gradual abundance changes occurs under frequent invasions, even with strong interactions.

Fast invasions lead to similar species abundances and regime shifts in community structure.

Abstract

It is well-known that interactions between species determine the population composition in an ecosystem. Conventional studies have focused on fixed population structures to reveal how interactions shape population compositions. However, interaction structures are not fixed, but change over time due to invasions. Thus, invasion and interaction play an important role in shaping communities. Despite its importance, however, the interplay between invasion and interaction has not been well explored. Here, we investigate how invasion affects the population composition with interactions in open evolving systems considering generalized Lotka-Volterra-type dynamics. Our results show that the system has two distinct regimes. One is characterized by low diversity with abrupt changes of dominant species in time, appearing when the interaction between species is strong and invasion slowly occurs. On the other hand, frequent invasions can induce higher diversity with slow changes in abundances despite strong interactions. It is because invasion happens before the system reaches its equilibrium, which drags the system from its equilibrium all the time. All species have similar abundances in this regime, which implies that fast invasion induces regime shift. Therefore, whether invasion or interaction dominates determines the population composition.