Thermal and salinity tolerance of feral and pet-traded cherry shrimp Neocaridina davidi (Bouvier, 1904).

Temperature and salinity are key abiotic factors influencing the physiology, distribution, and survival of aquatic organisms, yet their combined effects remain poorly understood, especially in landlocked freshwater decapods. We provide experimental data on the single and, for the first time, combined effects of temperature and salinity in atyid shrimps, focusing on Neocaridina davidi, an exotic and potentially invasive species widely traded in the aquarium industry. We used dynamic assays (CTmin, CTmax, and LTmax) and reaction norms to compare pet-traded and feral N. davidi populations with different life histories acclimated to 15-27°C and 0-10‰. These included the oldest known European population in a thermally and saline-polluted channel in Poland and recently established populations on Réunion Island. Overall, increased salinity reduced thermal tolerance. Despite being a landlocked freshwater shrimp, N. davidi exhibited moderate salinity tolerance, suggesting possible dispersal into low-to moderately saline brackish waters. However, ecological performance declined with rising salinity before physiological limits were reached. All populations showed thermal plasticity, though the magnitude of these responses varied among populations, consistent with differences in environmental history, phenotypic plasticity, and potentially genetic differentiation. These findings highlight the importance of both physiological plasticity and environmental context in shaping tolerance to interacting abiotic stressors when predicting invasion dynamics and the future distribution of this emerging invader.