# Insect population dynamics under Wolbachia-induced cytoplasmic incompatibility: Puzzle more than buzz in Drosophila suzukii

## TL;DR

This study explores how Wolbachia-induced reproductive failure affects fruit fly populations, finding that competition can counteract expected population declines.

## Contribution

The study reveals that competition can antagonistically interact with Wolbachia-induced cytoplasmic incompatibility, challenging previous theoretical predictions.

## Key findings

- Introducing wTei Wolbachia into Drosophila suzukii populations did not cause expected population decline.
- Strong negative density dependence was observed, but no Allee effect was detected.
- Competition interacts antagonistically with Wolbachia-induced cytoplasmic incompatibility.

## Abstract

In theory, the introduction of individuals infected with an incompatible strain of Wolbachia pipientis into a recipient host population should result in the symbiont invasion and reproductive failures caused by cytoplasmic incompatibility (CI). Modelling studies combining Wolbachia invasion and host population dynamics show that these two processes could interact to cause a transient population decline and, in some conditions, extinction. However, these effects could be sensitive to density dependence, with the Allee effect increasing the probability of extinction, and competition reducing the demographic impact of CI. We tested these predictions with laboratory experiments in the fruit fly Drosophila suzukii and the transinfected Wolbachia strain wTei. Surprisingly, the introduction of wTei into D. suzukii populations at carrying capacity did not result in the expected wTei invasion and transient population decline. In parallel, we found no Allee effect but strong negative density dependence. From these results, we propose that competition interacts in an antagonistic way with Wolbachia-induced cytoplasmic incompatibility on insect population dynamics. If future models and data support this hypothesis, pest management strategies using Wolbachia-induced CI should target populations with negligible competition but a potential Allee effect, for instance at the beginning of the reproductive season.