First assessment of the comparative toxicity of ivermectin and moxidectin in adult dung beetles: Sub-lethal symptoms and pre-lethal consequences

Among macrocyclic lactones (ML), ivermectin (IVM) and moxidectin (MOX) potentially affect all Ecdysozoan species, with dung beetles being particularly sensitive. The comparative effects of IVM and MOX on adult dung beetles were assessed for the first time to determine both the physiological sub-lethal symptoms and pre-lethal consequences. Inhibition of antennal response and ataxia were tested as two intuitive and ecologically relevant parameters by obtaining the lowest observed effect concentration (LOEC) values and interpolating other relevant toxicity thresholds derived from concentration-response curves (IC50, as the concentration of each ML where the antennal response is inhibited by half; and pLC50, as the quantity of ingested ML where partial paralysis was observed by half of treated individuals) from concentration-response curves. Both sub-lethal and pre-lethal symptoms obtained in this study coincided in that IVM was six times more toxic than MOX for adult dung beetles. Values of LOEC, IC50 and pLC50 obtained for IVM and MOX evaluated in an environmental context indicate that MOX, despite needing more time for its elimination in the faeces, would be half as harmful to dung beetles as IVM. This approach will be valuable to clarify the real impact of MLs on dung beetle health and to avoid the subsequent environmental consequences

Biomagnifcation and body distribution of ivermectin in dung beetles

We thank the staf of Doñana Biological Reserve (DBR-ICTS), Doñana National Park, and Los Alcornocales Natural Park, especially D. Paz, F. Ibáñez, P. Bayón, M. Malla and D. Ruiz for logistic facilities for the field work and permissions (2019107300000904/IRM/MDCG/mes) to collect cattle dung and dung beetles. We are grateful to J. Castro and A. Rascón for technical assistance. We also thank A. V. Giménez-Gómez for her technical assistance in the laboratory work. We thank also F.-T Krell and the two anonymous reviewers for their constructive comments. Financial support was provided by the project CGL2015-68207-R of the Secretaría de Estado de Investigación–Ministerio de Economía y Competitividad.A terrestrial test system to investigate the biomagnifcation potential and tissue-specifc distribution of ivermectin, a widely used parasiticide, in the non-target dung beetle Thorectes lusitanicus (Jekel) was developed and validated. Biomagnifcation kinetics of ivermectin in T. lusitanicus was investigated by following uptake, elimination, and distribution of the compound in dung beetles feeding on contaminated faeces. Results showed that ivermectin was biomagnifed in adults of T. lusitanicus when exposed to non-lethal doses via food uptake. Ivermectin was quickly transferred from the gut to the haemolymph, generating a biomagnifcation factor (BMFk) three times higher in the haemolymph than in the gut after an uptake period of 12 days. The fat body appeared to exert a major role on the biomagnifcation of ivermectin in the insect body, showing a BMFk 1.6 times higher than in the haemolymph. The results of this study highlight that the biomagnifcation of ivermectin should be investigated from a global dung-based food web perspective and that the use of these antiparasitic substances should be monitored and controlled on a precautionary basis. Thus, we suggest that an additional efort be made in the development of standardised regulatory recommendations to guide biomagnifcation studies in terrestrial organisms, but also that it is necessary to adapt existing methods to assess the efects of such veterinary medical products

Historical Isolation versus Recent Long-Distance Connections between Europe and Africa in Bifid Toadflaxes (Linaria sect. Versicolores)

Background: Due to its complex, dynamic and well-known paleogeography, the Mediterranean region provides an ideal framework to study the colonization history of plant lineages. The genus Linaria has its diversity centre in the Mediterranean region, both in Europe and Africa. The last land connection between both continental plates occurred during the Messinian Salinity Crisis, in the late Miocene (5.96 to 5.33 Ma). Methodology/Principal Findings: We analyzed the colonization history of Linaria sect. Versicolores (bifid toadflaxes), which includes c. 22 species distributed across the Mediterranean, including Europe and Africa. Two cpDNA regions (rpl32-trnL UAG and trnK-matK) were sequenced from 66 samples of Linaria. We conducted phylogenetic, dating, biogeographic and phylogeographic analyses to reconstruct colonization patterns in space and time. Four major clades were found: two of them exclusively contain Iberian samples, while the other two include northern African samples together with some European samples. The bifid toadflaxes have been split in African and European clades since the late Miocene, and most lineage and speciation differentiation occurred during the Pliocene and Quaternary. We have strongly inferred four events of post-Messinian colonization following long-distance dispersal from northern Africa to the Iberian Peninsula, Sicily and Greece. Conclusions/Significance: The current distribution of Linaria sect. Versicolores lineages is explained by both ancien