Environmental <scp>DNA</scp> supports importance of heterogeneous pond landscapes for arthropod diversity conservation

Abstract Freshwater ponds host diverse arthropod communities, but conservation frameworks are scarce. Heterogeneous pond mosaics of various sizes and successional stages can develop during raw material extraction in mining sites, acting as refugia for a variety of species. Here, we investigate arthropod diversity and conservation status across lakes and ponds in mining sites; analyze how water body size, age, and vegetation cover affect diversity patterns; and discuss how results can contribute to management actions and conservation schemes. Using environmental DNA metabarcoding, we determine arthropod diversity at 55 pond and lake plots located in active mining sites in Germany. We assess the effect of structural parameters on arthropod species richness, beta diversity, and the occurrence of rare and endangered species. Overall, we detected 436 arthropod species, many of which lacking a threat status evaluation, potentially hampering analyses of conservation aspects. We identify different effects of structural variables on species richness and beta diversity, and variable responses at the order level. Further, results reveal comparable diversity of accumulated pond network area, compared with single large water bodies of similar size, supporting high importance of heterogeneous pond networks for arthropod diversity conservation. Our study shows that systematic biodiversity management concepts both during active mining and at later stages of succession will be needed. Monitoring should go beyond just measuring taxonomic richness, including also assessments of community composition, the presence of rare and endangered taxa, and functional diversity.