Projecting seasonal and future thermal suitability of the invasive and commercially valuable Manila clam Ruditapes...

The Manila clam, Ruditapes philippinarum, is a commercially valuable non-native species that has successfully colonized European coastal ecosystems. Here, by integrating physiological experiments with a metabolic performance-based habitat suitability mapping approach, we investigate its thermal tolerance and habitat suitability in the Mediterranean Sea, with a focus on the Berre Lagoon. Using a respirometry-based thermal performance curve modelling, we quantified respiration rates across a temperature gradient and fitted a Thermal Performance Curve (TPC) selected via AICc comparison of 22 candidate models, with the Johnson and Lewin (1946) model providing best fit. The optimal temperature (T_opt) was identified at 32.89°C, with a narrow thermal safety margin of 1.49°C preceding the critical thermal maximum (CT_max) of 34.38°C. Seasonal and spatial projections of Thermal Habitat Suitability (THS) for the Mediterranean populations indicate that winter remains persistently unsuitable across present and future scenarios, with minimal change over time. Conditions appear to worsen in future spring, while improving in future summer and, to a lesser extent, in future autumn. Long-term monitoring in the Berre Lagoon indicated an increase in favorable thermal conditions over time, supporting the species' persistence. These findings demonstrate the critical role of integrating physiological thresholds into ecological models to support effective management under climate change. Furthermore, they improve our capacity to predict present and future dynamics of this invasive and commercially important species, including implications for its aquaculture under accelerating Mediterranean environmental change.