Authors: Ambrožová, Lucie;Zítek, Tomáš;Sládeček, František;Perlík, Michal;Kozel, Petr;Dostál, Dalibor; Jirků, Miloslav;Čížek, Lukáš;

Use of ivermectin negatively affects non-target dung beetles, which provide keystone ecosystem services for pasture functioning. Direct effects of ivermectin on dung beetles are well understood, but its long-lasting effects on real communities under field conditions remain unknown. We studied species richness, abundance, biomass and functionality (composition-mediated dung removal ability) of dung beetle communities in response to ivermectin treatment. Selected 15 ivermectin-treated and 11 untreated sites, both ≥5 consecutive years before sampling, covered wide range of climatic conditions in the Czech Republic, seasonal variability, and main herbivore dung types. Ivermectin-treated sites we selected into i) recently treated <8 weeks ago (immediate effects, lethal-sublethal residues levels) and ii) long-ago >8 weeks (lasting effects, sublethal to inconsequential residues levels). Ivermectin-treated sites had 35% lower species richness and 44% lower abundance, biomass did not change. From a functional perspective, ivermectin use significantly decreased the biomass of beetles with high contribution to dung removal (relocators, dwellers), while the biomass of beetles with low contribution (visiting adults, saprophagous larvae) was unaffected. Functionality, i.e., the dung removal ability of the community, was significantly reduced at treated sites. Effects of ivermectin use far beyond its physical presence have obvious negative consequences for pasture biodiversity and ecosystem functioning.