Drainage ditches as important habitat for species diversity and rare species of aquatic beetles in agricultural landscapes (Insecta: Coleoptera)

Beetle community in agricultural ditches

Agricultural drainage ditches are common structures in cultivated lowland areas across Europe. These artificial linear water bodies are interconnected to form networks that can offer valuable habitats for many water associated organisms. The current study contributes to the knowledge of aquatic Coleoptera biodiversity associated with artificial drainage ditches. Fundamental ecological and faunistical findings were combined with aspects relevant for applied nature conservation. Adult beetles were sampled at 124 sampling locations belonging to seven study sites in the federal state of Brandenburg, Germany. With 108 taxa out of 10 families the studied ditches showed a high species richness. Taxa associated with eutrophic conditions dominated with the dytiscid Hydroporus palustris as the most abundant species. In terms of β-diversity, a moderate turnover between the study sites could be observed. Although the sampling locations showed some degree of variability concerning habitat characteristics, measured environmental parameters only weakly explained observed differences in community composition. Beside taxonomical characterization of beetle diversity, aspects of functional diversity were analyzed. Interestingly, individuals with reduced flight ability were dominant. Because the predaceous family Dytiscidae dominated, beetles were mainly integrated as carnivores in the food web of ditches. Throughout the study, 13.0% threatened as well as 18.4% rare taxa could be recorded, referring to the German fauna of aquatic beetles. This may underpin the need to include agricultural drainage ditches into conservation management.