Identifying conservation hotspots and assessing species commonness and rarity: Baseline arthropod diversity in German nature reserves via national Malaise trap monitoring

Currently, knowledge of arthropod diversity and distributions in terrestrial habitats is limited due to a lack of taxonomists and consistent monitoring, hindering insect conservation efforts. To address this, we conducted an extensive country-wide study in Germany using a year-long Malaise trap monitoring effort supported by citizen scientists. Our study provides a benchmark of species occurrence in 21 German nature-protected areas. Metabarcoding methods revealed unexpectedly high small-scale and largely undescribed diversity, with 14,445 operational taxonomic units (OTUs) found. Of these OTUs, 8,589 were assigned to a species, but only 3,064 have been evaluated in German red lists. Seventeen invasive species were identified, five of which are potentially new records for Germany. High potential regional endemism was found, with 33% of OTUs detected in only one protected area, while widespread OTUs were rare making up 1.2% of the OTUs. Six protected areas showed significantly higher local contributions to beta diversity, emphasising the importance of protecting regionally diverse habitats.