Contrasting ecological impacts of geographically close invasive populations.

Intraspecific trait variability is now well recognized as a key component of biodiversity explaining how individuals within a species can differentially interact with their environment. To date, however, this concept has rarely been incorporated in the study of biological invasions, despite its provision of new insights into invasive species management. Here, we used an experimental approach to investigate how invasive red swamp crayfish (Procambarus clarkii) derived from geographically close ecosystems can differentially impact prey community structure and relevant ecosystem processes. We also compared the magnitude of the effects induced by invasive species introduction with those induced by intraspecific variability. Our results showed that effects of intraspecific variability can be strong for direct interactions such as resource (e.g., leaf litter, snails) consumption and of similar magnitude to the effects induced by the introduction of the invasive species when considering indirect interactions (e.g., primary production, ecosystem metabolism). Overall, these results highlighted that invasive populations of the same species are not ecologically equivalent, with each population acting differently on their recipient ecosystem.