Phenotypic responses of invasive species to removals affect ecosystem functioning and restoration.

Reducing the abundances of invasive species by removals aims to minimize their ecological impacts and enable ecosystem recovery. Removal methods are usually selective, modifying phenotypic traits in the managed populations. However, there is little empirical evidence of how removal-driven changes in multiple phenotypic traits of surviving individuals of invasive species can affect ecosystem functioning and recovery. Overcoming this knowledge gap is highly relevant because individuals are the elemental units of ecological processes and so integrating individual-level responses into the management of biological invasions could improve their efficiency. Here we provide novel demonstration that removals by trapping, angling and biocontrol from lakes of the globally invasive crayfish Procambarus clarkii induced substantial changes in multiple phenotypic traits. A mesocosm experiment then revealed that these changes in phenotypic traits constrain recovery of basic ecosystem functions (decomposition of organic matter, benthic primary production) by acting in the opposite direction than the effects of reduced invader abundance. However, only minor ecological impacts of invader abundance and phenotypic traits variation remained a year after its complete eradication. Our study provides quantitative evidence to an original idea that removal-driven trait changes can dampen recovery of invaded ecosystems even when the abundance of invasive species is substantially reduced. We suggest that the phenotypic responses of invaders to the removal programme have strong effects on ecosystem recovery and should be considered within the management of biological invasions, particularly when complete eradication is not achievable.