Taxonomic status of Cyathostoma nematodes (Nematoda: Syngaminae) parasitizing respiratory tracts of birds of prey and owls in Europe and North America: how many species are there?

So far, the identity of Cyathostoma (Hovorkonema) nematodes collected from respiratory tracts of birds of prey (Accipitriformes, Falconiformes) and owls (Strigiformes) in Europe and North America is extremely inconsistent. Our results, based on analyses of ITS-2 sequences suggest that the Cyathostoma (Hovorkonema) nematodes found in the birds of prey and owls from Central Europe and North America probably belong to the same species, C. (Hovorkonema) americana Chapin, 1925. We are convinced, that described in recent literature high ITS-2 divergence among C. (Hovorkonema) nematodes collected from Europe, has occurred as a result of invalid synonimisation of some C. (Hovorkonema) species. In our opinion C. (Hovorkonema) americana (typically parasites of tracheae and air sacs of raptors) and C. (Hovorkonema) variegatum (Creplin, 1849) (typically parasites of tracheae of cranes and storks) are valid molecular and morphologically distinct species.