Fight club, or the story of the invasion of two marine blue crab species in the Mediterranean Sea

Climate change and anthropogenic pressures are driving the expansion of marine species, influencing organism performance, population dynamics, and ecosystem structure. In the Mediterranean Sea, the invasive American blue crab, Callinectes sapidus , and the Red Sea blue crab, Portunus segnis , are expanding their ranges in response to accelerated ocean warming. This study analyzes their Thermal Performance curves (TPCs) to predict co-occurrence and dominance under climate scenarios. Callinectes sapidus thrives in cooler temperatures, while P. segnis is better adapted to warmer environments. These patterns indicate a latitudinal partitioning driven by temperature tolerance, with only limited temporal overlap during the warmest months. Notably, while coexistence in 2023 was rare and spatially restricted, by 2050 these zones become more extensive and frequent, especially from July through October, indicating a future rise in interspecific interactions. These future projections indicate that rising temperatures will favor P. segnis , increasing competition and co-occurrence with C. sapidus , particularly in summer. The study highlights the importance of understanding temperature-driven physiological traits in shaping invasive species interactions and developing tools for management. Maps generated from TPCs and thermal dominance indices inform risk management plans and conservation efforts, helping to mitigate the ecological and socio-economic impacts of these invasive species.