Repeated invasions cause destabilisation of functional networks.

Microbial invasions are a common occurrence. Previous studies have shown that the invasion resistance is directly linked to the properties of the resident community, however, these have only been considered as isolated events. Using an experimental approach we test whether naturalised bacterial communities change their function when faced with the challenge of subsequent invasion events. Our results indicate that there were significant disruptions to the overall functioning of the community that are linked with responding to a perturbation. Further, we observe a reduction of the contribution of rare species with increased invasion, that suggested an overall destabilisation of the community. Whilst further investigation is warranted to understand long term impacts, this report demonstrates that there are functional consequences of microbial invasions, that are not obvious from changes in community composition.