Among demons and killers: current and future potential distribution of two hyper successful invasive gammarids

Biological invasions represent one of the main contemporary pressures facing freshwater ecosystems, and a better understanding of invasive species potential distributions is essential to prepare for future stressors. Crustacean invaders contribute significantly to global invasions with the Ponto-Caspian region being one of the primary donor areas for the Palearctic. The amphipods Dikerogammarus villosus and Dikerogammarus haemobaphes, popularly known as “killer” and “demon” shrimps, are emblematic of successful Ponto-Caspian invaders of European freshwaters. However, the geographical areas in which the abiotic environment is potentially suitable for them have not been investigated. To address this gap, current and future potential distributions were studied for the European Western Palearctic considering two scenarios and time periods (2050 and 2070) as well as the association between anthropogenic activities and individual species habitat suitability. Results show large areas of central-western Europe are currently suitable for both species and indicate some potential for range expansion within colder European areas. In particular, D. haemobaphes has the potential to expand its range further west and within southern parts of Europe. Scenarios of future climate change don’t provide evidence for further range expansion compared to the current conditions and suggest a reduction of range overlap within the most suitable areas. Results reveal lowland areas are at greatest risk of colonisation as well as a significant association with anthropogenic activities for both amphipods. The outcomes of the research could be used by resource managers for preparing and managing future changes of both species distributions and facilitate decision-making for monitoring and control.