Ecophysiology of Yucca gloriosa in a Mediterranean sand dune environment

The C3–CAM (crassulacean acid metabolism) intermediate species Yucca gloriosa L. is invading coastal dunes in central Italy, causing a loss in biodiversity and habitat. In order to investigate its competitive success, a number of ecophysiological traits were analysed: CAM activity (through carbon isotope composition, δ13C, and cell acidification), photochemical efficiency of PSII (operating and maximum photosystem II quantum yield), stomatal conductance, relative water content, and succulence index (SI). Analyses were conducted over the course of one year, to assess yucca’s response to seasons and the shoreline-inland ecological gradient. The species displayed high physiological plasticity, a factor that might prove decisive in enhancing carbon fixation and water-use efficiency across the seasons, and accordingly its level of invasiveness. Temperature seemed crucial in controlling photosynthetic metabolism, a fact borne out by seasonal changes seen in δ13C and SI. Some stress symptoms appeared in winter, including a slight reduction of photochemical performance, and the shoreline–inland ecological gradient did not have any significant effects. All the plants analysed were intermediate C3–CAM: given that yucca cannot reproduce sexually in Europe, the entire population of the area studied might conceivably share the same carbon fixation pathway. The results obtained may help afford a better understanding of the ecophysiological features of Y. gloriosa in a Mediterranean dunal ecosystem, along with the dynamics of the invasion process, allowing a more efficient approach to be adopted in programmes for managing this environment.