The taxonomic identity of Central and Northern European Simulium (Nevermannia) (Diptera, Simuliidae): molecular, morphological, and ecological data

DNA barcoding based on the cytochrome c oxidase subunit I (COI) gene is increasingly employed in blackfly taxonomy to resolve identification challenges within species complexes. This study evaluates two competing hypotheses: whether the populations of the subgenus Nevermannia in Central Continental Europe represent three distinct species (Simulium angustitarse, S. lundstromi, and S. volhynicum) as traditionally recognised, or a single, highly plastic species complex. To test these models, samples were collected from the Ukrainian Polissia (Volyn Region) and compared with datasets from Finland, Germany, Bulgaria, and the United Kingdom. While populations in the Carpathians and the Balkans may exhibit greater genetic divergence, our results demonstrate that the populations from Volyn are conspecific with those from Finland — the type locality of S. angustitarse. Despite notable morphological and ecological variation, the lack of significant molecular differentiation across this Continental European range supports the hypothesis of a single, highly plastic species complex. Consequently, Simulium angustitarse Lundstrom, 1911 is established as a senior synonym of Simulium volhynicum (Usova & Sukhomlin, 1990), syn. n.