Differential effects of increasing temperature on the germination of five wild species with varying range sizes in a Carrara marble quarry

Assessing the performance of spontaneous plants in abandoned quarries under future environmental scenarios is important for successful restoration practices. Air warming is one of the most relevant ongoing climatic changes in the Mediterranean. We tested the effects of increasing temperature on the germination of five species spontaneously colonising the abandoned sectors of a Carrara marble quarry (Tuscany, central Italy). We selected five plant species with different widths of their distribution range, from local endemic to invasive alien: Santolina pinnata, Globularia incanescens, Hypericum coris, Helichrysum italicum, and Buddleja davidii. Seeds were collected in situ and their germination was tested in laboratory conditions at 10, 15, 20, 25, and 30°C. The effects of temperature and species on germination percentage (GP) and mean germination time (MGT) were tested through two-way ANOVA. Increasing temperatures negatively affected the GP of S. pinnata and H. coris. G. incanescens performed better at intermediate temperatures, while H. italicum benefited from increasing temperatures. B. davidii showed a similar high GP under all the treatments. MGT decreased with increasing temperature for all the species, except for S. pinnata, which showed an increase of MGT with increasing temperature. We highlighted that, under future warmer climatic conditions, the two endemic species will be disadvantaged with respect to the species with a wider distribution range and the non-native species in the studied quarry. This evidence is relevant for restoration planning since seeding the two endemic species could be unsuccessful under future environmental scenarios, when H. italicum and B. davidii will be more competitive in the colonisation of the quarry.