Phylogeny of hymenolepidid cestodes (Cestoda: Cyclophyllidea) from mammalian hosts based on partial 28S rDNA, with focus on parasites from shrews.

Abstract

The aims of the study are to enrich the partial 28S rDNA dataset for hymenolepidids by adding new sequences for species parasitic in the genera Sorex, Neomys and Crocidura (Soricidae) and to propose a new hypothesis for the relationships among mammalian hymenolepidids. New sequences were obtained for Coronacanthus integrus, C. magnihamatus, C. omissus, C. vassilevi, Ditestolepis diaphana, Lineolepis scutigera, Spasskylepis ovaluteri, Staphylocystis tiara, S. furcata, S. uncinata, Vaucherilepis trichophorus and Neoskrjabinolepis sp. The phylogenetic analysis (based on 56 taxa) confirmed the major clades identified by Haukisalmi et al. (Zool Scr 39:631-641, 2010) based on analysis of 31 species: Ditestolepis clade, Hymenolepis clade, Rodentolepis clade and Arostrilepis clade; however, the support was weak for the early divergent lineages of the tree and for the Arostrilepis clade. Novelties revealed include the molecular evidence for the monophyly of Coronacanthus, the non-monophyletic status of Staphylocystis and the polyphyly of Staphylocystoides. The analysis has confirmed the monophyly of Hymenolepis, the monophyly of hymenolepidids from glirids, the position of Pararodentolepis and Nomadolepis as sister taxa, the polyphyly of Rodentolepis, the position of Neoskrjabinolepis and Lineolepis as sister taxa, and the close relationship among the genera with the entire reduction of rostellar apparatus. Resolved monophyletic groups are supported by the structure of the rostellar apparatus. The diversification of the Ditestolepis clade is associated with soricids. The composition of the other major clades suggests multiple evolutionary events of host switching, including between different host orders. The life cycles of Coronacanthus and Vaucherilepis are recognised as secondarily aquatic as these taxa are nested in terrestrial groups.