Delaying drought-driven leaf cells damages may be the key trait of invasive trees for ensuring their success in the Mediterranean basin.

Invasive alien species (IAS) threaten the biodiversity richness of Mediterranean basin, a drought-prone region. However, our knowledge on IAS adaptative strategies for facing Mediterranean drought summers is still incomplete. The aim of the present study is to compare the water relations and the critical relative water content (RWC) values leading to loss of cell rehydration capacity of two Mediterranean basin IAS (i.e., Ailanthus altissima and Robinia pseudoacacia) versus two co-occurring native species (i.e., Fraxinus ornus and Quercus pubescens). Study IAS showed higher values of water potential at turgor loss point and osmotic potential at full turgor, lower values of modulus of elasticity and leaf mass area but higher photosynthesis rate, even during the summer, respect to the Mediterranean native species. These findings supported the hypothesis that IAS are characterized by a resource acquisitive strategy coupled with a safety-efficiency trade-off, compared to Mediterranean native species. However, similar leaf RWC thresholds leading to loss of cell rehydration capacity were recorded in the two groups of species. Moreover, IAS showed higher saturated water content and capacitance values compared to the co-occurring species. Overall, our results suggest that the success of Mediterranean IAS is driven by their ability to delay dehydration damages of mesophyll cells during Mediterranean summer drought, thereby supporting their distinctive high carbon assimilation rate.