Combining functional originality and risk – Novel perspectives on conservation prioritization of fishes in the Western Mediterranean Sea

Identifying functionally original species, i.e., species with distinct combinations of phenotypic traits, helps to bridge the gap between the reality of taxonomic conservation priorities and conserving ecosystem integrity. Few studies consider functional originality to date, although it is well established that functionally original species disproportionately contribute to ecosystem functions and stability and are often rare or threatened. For the first time at this regional scale, we identified the most functionally original fish species in the Western Mediterranean Sea – one of the most diverse but strongly impacted marine ecosystems globally. Building on the recently proposed “FUSE” indicator framework, we weighed functional originality by different risk metrics: the IUCN Red List status, scarcity, and trait-based scores of sensitivity to fishing pressure or climate change. Our results demonstrate the value of trait-based approaches for conservation prioritization and highlight the vulnerability and functional importance of k-strategist fish species. Additionally, we observed considerable variability in the spatial distributions of functional originality and risk and highlighted spatial conservation priorities. These results contribute to conservation planning in the Western Mediterranean Sea from a novel and important functional perspective and constitute a proof-of-concept for combined species-level indicators of functional originality and risk.