# Translating macroecological models to predict microbial establishment probability in an agricultural inoculant introduction

## TL;DR

This study adapts a macroecological model to predict how microbial inoculants establish in agricultural systems, focusing on the role of propagule pressure.

## Contribution

The paper introduces an experimental and modeling framework to predict microbial inoculant establishment using macroecological principles.

## Key findings

- Repeated inoculant applications can increase establishment probability even without higher concentration.
- The risk-release relationship was experimentally determined for Pseudomonas simiae in a monocot system.
- Simulations show that application frequency is a key factor in microbial establishment.

## Abstract

The use of potentially beneficial microorganisms in agriculture (microbial inoculants) has rapidly accelerated in recent years. For microbial inoculants to be effective as agricultural tools, these organisms must be able to survive and persist in novel environments while not destabilizing the resident community or spilling over into adjacent natural ecosystems. Despite the importance of propagule pressure to species introductions, few tools exist in microbial ecology to predict the outcomes of agricultural microbial introductions. Here, we adapt a macroecological propagule pressure model to a microbial scale and present an experimental approach for testing the role of propagule pressure in microbial inoculant introductions. We experimentally determined the risk-release relationship for an IAA-expressing Pseudomonas simiae inoculant in a model monocot system. We then used this relationship to simulate establishment outcomes under a range of application frequencies (propagule number) and inoculant concentrations (propagule size). Our simulations show that repeated inoculant applications may increase establishment, even when increased inoculant concentration does not alter establishment probabilities. Applying ecological modeling approaches like those presented here to microbial inoculants may aid their sustainable use and provide a monitoring tool for microbial inoculants.