Molecular phylogeny, morphological diversity, and species’ distribution of cestodes of the genus Neoskrjabinolepis Spassky, 1947 (Cestoda: Hymenolepididae) in the Palaearctic

Morphological and genetic diversity of species of the cestode genus Neoskrjabinolepis, which parasitise Sorex shrews and are widespread in the Palaearctic, was studied. A set of morphological characteristics is presented. Because the type material of Neoskrjabinolepis schaldybini has been lost, a neotype from the type host Sorex araneus and from a region close to the type locality (Altai Republic, Russia) was designated. Host specificity and the geographical distribution of Neoskrjabinolepis species were analysed. Of the 17 species of Neoskrjabinolepis, four species parasitise hosts in the European part of the Palaearctic, 16 in the Asian part and two in the Nearctic. Neoskrjabinolepis cestodes in 16 species of Sorex have been recorded to date. High endemism (40%) and euryxeny of Neoskrjabinolepis were observed. Phylogenetic analysis based on partial sequences of the 28S rRNA gene and of the mitochondrial nad1 gene revealed significant genetic diversity of Neoskrjabinolepis species. The level of interspecific divergence was established at 0.2–1.7% for the 28S rRNA gene and 4.4–19.4% for the nad1 gene. The molecular data showed some genetic lineages that may represent separate species. Complicated genetic structure of N. schaldybini and N. merkushevae, primarily in the Caucasus, was demonstrated, suggesting that these species are composite taxa.