Alien and native seed germination performance might shape the species assembly of temperate grasslands under a global warming scenario

Global warming is rapidly altering our ecosystem in terms of biodiversity, functions and services loss. The rising temperatures have often shown the ability to enhance biological invasion by facilitating spread and growth of alien species in the new lands. The success of plant invasion requires the overcome of multiple biological barriers. Among the crucial life stages, seed germination greatly contributes to the final species assembly of plant community. Several studies have already suggested that alien plant success is likely linked to their high seed germination rates and longevity. We hypothesized these traits to be further enhanced by future temperature rise. Among terrestrial ecosystems, temperate dry grasslands are considered important hotspot of biodiversity, but also among the most prone ecosystems to biological invasions. In these habitats, Asteraceae is one of the most represented family, in terms of abundance and number of species, for both alien and native plants. In this scenario, we designed a germination test experiment at two temperatures (i.e., 22ºC and 28ºC) including common Asteraceae grassland species, considering native and alien species (split into archaeophyte and neophyte). Our aim was to test the relationship between seed germination, temperature, and their interaction with alien status. The test was performed on both separated and mixed pools of species by using a full-factorial orthogonal design. We expect to find a decrease/delay in native species germination compared with alien seeds with the increasing temperature. We also suppose alien species germination to affect the final species assembly of mixed germination plates, by inhibiting local species germination, also in the light of plausible allelopathic interactions. These results will give important information on future management actions aimed at curbing alien plant invasions, by improving our knowledge on seed-bank response and interactions mechanisms of common species occurring in natural disturbed areas or restoration sites.