Unravelling climate risks for plant regeneration by seed in the Mediterranean

Studying plant regeneration from seeds enhances our understanding of plant responses to climate change and supports conservation and ecological restoration strategies. However, knowledge of Mediterranean seed germination is often based on individual species or local studies, lacking an integrated view for this biodiversity hotspot. While open-access germination data can reveal broad-scale patterns, their adequacy for species-level niche-modelling remains unclear, potentially jeopardizing conservation and restoration efforts. The main goal of this project is to identify native flowering plants from the Mediterranean Basin exhibiting germination niches compatible with current and future warming scenarios. To this end, we implemented a four steps workflow developed during the time of this PhD project. (1) We identified the potential pool of species for seed-based conservation and restoration activities in the Mediterranean and we compiled the seed germination data for these species by creating MedGermDB, the first database of primary germination data of Mediterranean species. (2) We then applied a multi-species approach to test the Mediterranean seed germination syndrome hypothesis identifying biome-level germination patterns. Despite these data revealed broad-scale patterns of the germination niche in the Mediterranean, it was unclear if the available data were also adequate to adopting a fine-niche-germination modelling. Therefore, (3) we assessed the germination data availability and quality to model seed germination thermal responses to identify species exhibiting germination syndromes compatible with current and future warming scenarios. Whilst we highlighted the prospect for modelling the thermal seed germination niche and the identification of species at potential thermal risk, we stressed the need to produce new high-quality, species-specific germination data to access knowledge of climate risks for a wider range of species. In consequence, to demonstrate the type and quantity of data necessary to increase our germination knowledge under a climate change perspective, as a final task of this project (4) we generated new laboratory-based detailed germination data for three habitat-specialist annual back dune species and identified their thermal limits for seed germination and their tolerance to water stress. We demonstrated that ecological, evolutionary, and biogeographical questions can be addressed using multi- and single-species approaches. Our models effectively explore germination responses under various conditions, providing useful methods for quantifying germination strategies in the Mediterranean. But we also highlighted the need of expanding and integrating germination data to improve conservation efforts and address ecological and evolutionary questions at finer scales. It underscores the importance for enhanced collaborations between researchers and policymakers to ensure that conservation priorities align with empirical data, supporting more effective seed-based conservation and restoration strategies in the face of climate change.