Molecular phylogeny and systematics of cestodes with rudimentary rostellum (Cestoda: Hymenolepididae) from Holarctic Sorex shews (Eulipotyphla: Soricidae)

We analyse the phylogenetic relationships and taxonomic status of hymenolepidid cestodes with rudimentary rostellum, parasitic in Holarctic shrews of the genus Sorex. These cestodes were previously termed as a ‘Ditestolepis clade’ and encompass eight genera: Diorchilepis, Ditestolepis, Ecrinolepis, Gulyaevilepis, Mathevolepis, Novobrachylepis, Spalania and Spasskylepis. Representatives of seven of these were available for molecular study, including type species of all seven genera. Phylogenetic analysis based on partial sequences of the 28S rRNA gene supports this group of genera as monophyletic. The ‘Ditestolepis clade’ consists of two subclades. One of these includes genera containing cestodes having suckers positioned inside bothrium-like depressions (Ditestolepis, Gulyaevilepis and Spasskylepis). The second subclade contains cestodes with suckers expanding far beyond the margins of the scolex (Mathevolepis, Ecrinolepis, Spalania and Novobrachylepis). The relative taxonomic value of several additional morphological characters is discussed. Genetic data convincingly demonstrate that Ditestolepis diaphana, Spasskylepis ovaluteri and Mathevolepis macyi represent complexes of morphologically similar species. Based on the phylogenetic analysis, we resurrect the genus Spalania. Amended generic diagnoses and keys to identification of the genera in the Ditestolepis clade, as well as keys to the known species, are provided.