Salinity, not only temperature, drives tropical fish invasions in the Mediterranean Sea, and surface-only variables explain it better

The increasing success of invasive warm water species is often explained as a direct consequence of a warming climate, but other environmental variables are seldomly taken into account. Here, running RandomForest models with many combinations of relatively uncorrelated environmental predictors, we investigate the factors influencing the distribution of Red Sea fishes in the Mediterranean Sea, which was invaded through the Suez Canal. Our results highlighted the fundamental role of salinity, not only temperature, in determining the distribution of these tropical species, with average values (primarily salinity and surface sea temperatures) performing the best of the respective groups. Noteworthy, models based on surface variables only resulted in higher evaluation scores than those including also bottom variables. These findings contribute to identifying the most relevant factors that explain tropical fish distribution in the Mediterranean Sea and provide advice to the selection of environmental variables in species distribution modeling.