The Invasion Criterion: A Common Currency for Ecological Research

Area of Science:

• Ecology
• Community Ecology
• Theoretical Ecology

Background:

• Stable coexistence is traditionally assessed using the invasion criterion.
• The invasion criterion posits that all species must increase in abundance when rare for stable coexistence.
• This principle is increasingly applied across diverse ecological fields, including eco-evolutionary dynamics, global change, and macroecology.

Purpose of the Study:

• To identify the invasion criterion as a unifying concept in emerging ecological theory.
• To connect this theoretical framework with practical methods for testing species coexistence.
• To highlight the underutilization of straightforward methods for assessing the invasion criterion.

Main Methods:

• Literature review to identify the prevalence of the invasion criterion in contemporary ecological theory.
• Synthesis of theoretical advancements across different ecological sub-disciplines.
• Identification and discussion of existing, yet underused, methods for empirically testing the invasion criterion.

Main Results:

• The invasion criterion serves as a common theoretical foundation across various ecological fields.
• New theoretical developments increasingly rely on the invasion criterion.
• Accessible methods for testing the invasion criterion are available but not widely adopted.

Conclusions:

• The invasion criterion is a fundamental principle linking diverse areas of ecological research.
• Integrating the invasion criterion with its testing methods can advance ecological understanding.
• Promoting the use of established methods can facilitate empirical validation of coexistence theory.