title: Ivermectin sensitivity is an ancient trait affecting all ecdysozoa but shows phylogenetic clustering among sepsid flies.
abstract: Avermectins are potent and popular veterinary pharmaceuticals used globally to fight parasites of livestock and humans. By disturbing ion channel transport through the membrane, avermectins are effective against endo- and ectoparasitic round and horsehair worms (Nematoida), insects, or ticks (Arthropoda), but not against Plathelminthes, including flatworms (Trematoda) and tapeworms (Cestoda), or segmented worms (Annelida). Unfortunately, excreted avermectins have strong nontarget effects on beneficial arthropods such as the insect community decomposing livestock dung, ultimately impeding this important ecosystem function to the extent that regulators mandate standardized eco-toxicological tests of dung organisms worldwide. We show that the ancient phylogenetic pattern and qualitative mechanism of avermectin sensitivity is conserved and compatible with most recent phylogenomic hypotheses grouping the Nematoida with the Arthropoda as Ecdysozoa (molting animals). At the species level, we demonstrate phylogenetic clustering in ivermectin sensitivities of 23 species of sepsid dung flies (Diptera: Sepsidae). This clustered 500-fold quantitative variation in sensitivity may indicate recent lineage-specific responses to selection, but more likely reflects pre-existing genetic variation with pleiotropic effects on eco-toxicological responses to pollutants. Regardless, our results question the common practice in eco-toxicology of choosing single test species to infer detrimental effects on entire species communities, which should ideally assess a representative taxonomic sample.
authors.affiliation: Institute of Evolutionary Biology and Environmental Studies, University of Zürich-Irchel Zürich, Switzerland ; Department of Biological Sciences, National University of Singapore Singapore, Singapore ; Department of Biology, Life Sciences Complex, Syracuse University 107 College Place, Syracuse, NY, 13244, USA.
authors.forename: Nalini
authors.initials: N
authors.lastname: Puniamoorthy
authors.affiliation: Institute of Evolutionary Biology and Environmental Studies, University of Zürich-Irchel Zürich, Switzerland.
authors.forename: Martin A
authors.initials: MA
authors.lastname: Schäfer
authors.affiliation: ECT Oekotoxikologie GmbH Flörsheim, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Römbke
authors.affiliation: Department of Biological Sciences, National University of Singapore Singapore, Singapore.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Meier
authors.affiliation: Institute of Evolutionary Biology and Environmental Studies, University of Zürich-Irchel Zürich, Switzerland.
authors.forename: Wolf U
authors.initials: WU
authors.lastname: Blanckenhorn
keywords: Sepsidae; drug resistance; dung insects; eco-toxicological traits; environmental impact studies; exaptation; ivermectin; livestock medication; phylogeny