Molecular-genetic-based contribution to the taxonomy of theAcanthocyclops robustusgroup

Long-standing taxonomic problems involving the Acanthocyclops robustus–vernalis complex of freshwater cyclopoids have not been resolved. After Kiefer's designation of A. robustus Sars as an older synonym of Acanthocycops americanus Marsh, a lot of data indicating their differentiation have been accumulated. To handle this taxonomical problem, representative populations from type localities of the respective taxa and from other European and US sites were analyzed morphologically and genetically using mitochondrial COI and 12S rRNA. Molecular-genetic analysis revealed that the three species described at the end of the nineteenth century: A. robustus, A. americanus and A. vernalis are well-sep…