Conservation prioritization typically relies on the IUCN Red List, yet these frameworks may not adequately capture the diversity of functional traits in assessed taxa. Calculations of functional, phylogenetic and evolutionary uniqueness have been applied at large geographical scales, although at the national scale they may have practical applications to increase efficiency of targeted conservation. Using trait data from the TRY Plant Trait Database, we quantified functional distinctiveness for 2,359 spermatophytes, 50 pteridophytes and 661 bryophytes in Italy, using Gower's distance and we identified functionally rare taxa as those falling at the extremes of the mean dissimilarity distribution. A novel approach involved calculating functional distinctiveness for growth-related and reproductive traits, rather than combining all traits into a single metric as done conventionally. We tested whether inclusion in IUCN assessments and conservation status categories, scopes (assessed nationally only vs assessed in other lists) and policy coverage (Habitats Directive, Bern Convention, CITES) is predicted by functional rarity using phylogenetically-informed logistic models accounting for geographic range size and endemism status. Finally, we tested a novel binary rarity index - defined as the count of traits for which each species falls at distributional extremes - and compared its predictive power to that of functional distinctiveness. Preliminary results showed that functional rarity calculated with growth and reproductive traits predicts likelihood of assessment and policy inclusion better than overall functional distinctiveness. Furthermore, the rarity index based on extremes of trait values predicted IUCN assessment inclusion and category more accurately than functional distinctiveness.

At its completion, this research will provide a detailed account of trait and phylogeny-based rarity for each Italian plant species and serve as case study to advocate for the integration of functional traits into red-listing and policy-design processes.