Short range shifts in plant physiological responses to induced water stress: experimental evidence of intraspecific trait variability differentiating neighbouring Mediterranean plant populations

Mediterranean plants are facing increased periods of drought, potentially jeopardizing their survival. Despite the known influence of intraspecific variability on plants’ responses to the environment, most studies focus on differences between species and overlook short distances. Following the observation of three nearby populations of Quercus ilex and Cistus salviifolius inheriting different sets of drought-related functional traits in common garden, we tested if these populations could perform differently under water stress. We observed drought responses on plantlets from both species, measuring key physiological traits such as gas exchanges and spectrometric indexes. Our results show similar responses from populations of C. salviifolius while Q. ilex had high intraspecific variability, with increased drought-resistance in plants hailing from dry provenances, reflected by improved water use efficiency, photosynthetic capacity, and reduced metabolic response to stress. These observations support the idea that, despite the short distances, neighbouring plant populations can adapt differently to drought, changing the way they withstand climate and its changes.