Assessing Habitat Suitability and Distribution Patterns of the Invasive Brachyuran Crabs Callinectes sapidus and Portunus segnis in the Mediterranean Basin

In this study, we investigate the habitat suitability and distribution patterns of two invasive alien crab species, Callinectes sapidus and Portunus segnis, in the Mediterranean basin. Using a comprehensive dataset compiled from multiple sources, including bibliographic records, online databases, and online informal sources, we mapped the occurrences of these species and overlaid them with environmental variables obtained from the Copernicus Marine Service. We employed MaxEnt species distribution models to predict habitat suitability, considering variables such as sea surface temperature, salinity, chlorophyll, and oxygen. Our results indicate widespread distribution of C. sapidus across the basin, with notable concentrations in certain areas, while P. segnis exhibits a predominantly southern distribution. Model evaluations demonstrate high predictive performance, with average AUC (area under the receiver operating characteristic curve) values exceeding 0.85. Additionally, we assessed potential habitat overlap between the two species at different probability thresholds, revealing regions where coexistence is likely. Our findings provide valuable insights into the spatial dynamics of invasive alien crab species in the Mediterranean and contribute to ongoing efforts in biodiversity conservation and management.