Synthesising the trait information of European Chironomidae(Insecta: Diptera): Towards a new database

tChironomidae are among the most conspicuous and ecological diverse group of freshwater invertebrates.They may dominate unimpacted communities in abundance and biomass, accounting for more than 50%of macroinvertebrate species in standing and flowing waters. In deep zones of eutrophic lakes and highlyhuman-impacted streams, they are often the only family of aquatic insects remaining. In bioassessmentprogrammes, Chironomids are often identified at the family and subfamily levels, due to difficulties inthe taxonomic identification of larvae resulting from a high intrinsic morphological similarity. This maypotentially result in bias as, similarly to Ephemeroptera, Trichoptera or Plecoptera, Chironomidae species,which are replaced along natural and human-impacted gradients due to differences in their ecologicalrequirements. Recently, multiple trait-based approaches have been proposed to complement taxonomic-based assessment of streams and rivers using macroinvertebrates. However, the lack of specific traitinformation for Chironomidae prevents their use in the functional assessment of communities. Therefore,here, we aimed to: (1) develop a trait database for European Chironomidae genera that can be used infuture bioassessment and ecological studies; (2) evaluate, by multivariate analyses, whether our newdatabase provides additional information on Chironomidae compared to the trait information providedin the commonly used European trait database (Tachet et al., 2010); and (3) determine whether thenew information on Eltonian traits (proxy to biological traits) translates the most accepted phylogeneticrelationships among Chironomidae subfamilies. We gathered information on 744 species and 178 genera,for 37 traits covering 186 trait categories, and found substantial differences between our database and thecommonly used European trait database. In addition, available information on traits was not always inagreement with phylogenetic relationships among subfamilies. Orthocladiinae and Chironominae whichare considered sister groups in evolutionary terms actually showed confident trait relatedness based onEltonian traits tree while the remaining relationships between subfamilies are questionable. In addition,different traits can occur in closely related taxa depending on the environmental drivers operating ontheir habitats. Our study reveals that the usually accepted redundancy within the Chironomidae familyand subfamilies must be a product of averaging the information from finer taxonomic resolution addedto the substantial lack of information for this insect group