Linking species traits and vulnerability indicators in European Odonata

Understanding the mechanisms and commonalities driving species' vulnerability is essential for prioritizing and guiding conservation efforts. Trait-based approaches offer a mechanistic foundation for generalizing species vulnerabilities within a taxonomic group. Here, we assess how the vulnerability of European Odonata is associated with their traits. Our aim was to (1) quantify the link between traits and vulnerability and (2) identify the most important traits in a multi-trait context. For 123 species, we linked 3 vulnerability indicators (Red List categories, distribution trends and areas of occupancy) to a dozen traits, using discriminant and redundancy analyses. We find that 48 to 64% of the variability in vulnerability indicators is explained by traits. The main traits related to vulnerability are habitat, voltinism and thermal preferences. More specifically, vulnerable species tend to associate with oligotrophic habitats or Mediterranean streams. They also tend to have longer life cycles, but this relationship is reversed for species with a small area of occupancy. Species vulnerable because of their decreasing distribution tend to have cold thermal preferences. Vulnerable species generally show a narrow thermal range (except for species vulnerable because of their decreasing distribution). Assessing species' vulnerability is crucial to inform conservation: our trait-based approach provides clues regarding pressures responsible for species vulnerability, thus allowing to plan conservation action targeting groups of species sensitive to the same pressures, rather than focusing on individual species. Our method provides novel opportunities for predicting species' vulnerability, and paves the way for building a multi-species conservation indicator for Odonata.