Systematic relationships of hymenolepidid cestodes of rodents and shrews inferred from sequences of 28S ribosomal RNA

Abstract

Henttonen, H. (2010). Systematic relationships of hymenolepidid cestodes of rodents and shrews inferred from sequences of 28S ribosomal RNA. -Zoologica Scripta, 39, 631-641. This study attempts to elucidate systematic relationships of hymenolepidid cestodes of rodents (18 species), shrews (13 species) and bats (one species) using sequences of partial 28S ribosomal RNA, with special reference to the genus Rodentolepis. The main finding is the presence of four multispecies clades of hymenolepidid cestodes showing pronounced morphological variation and frequent colonizations between unrelated hosts. Neither the hymenolepidid cestodes of shrews nor rodents were monophyletic. Also, the genus Rodentolepis sensu Vaucher in Czaplinski & Vaucher (1994, Keys to the Cestode Parasites of Vertebrates. Commonwealth Agricultural Bureaux International, Cambridge) is clearly nonmonophyletic. Although rostellar morphology is obviously a key feature on specific and generic levels, on higher systematic levels it seems to be a rather poor indicator of phylogenetic affinity in hymenolepidid cestodes. The presence of clades with more than one rostellar type (armed rostellum present, rudimentary unarmed rostellum present and rostellum absent) also conflicts with the proposed subfamilial and tribal classifications of hymenolepidid cestodes. The overall evidence suggests that the recent trend of splitting hymenolepidid cestodes into multiple genera will produce a more stable and practical classification than the earlier practice of favouring a few, morphologically variable genera. New classifications of hymenolepidid cestodes should, however, consider both morphological and molecular evidence.

Hymenolepis folkertsi n. sp. (Eucestoda: Hymenolepididae) in the oldfield mouse Peromyscus polionotus (Wagner) (Rodentia: Cricetidae: Neotominae) from the southeastern Nearctic with comments on tapeworm faunal diversity among deer mice

“…Phylogeny Spassky (1992) considered hymenolepidids with an unarmed scolex parasitizing mammalian hosts to be paraphyletic. Recent molecular phylogenetic studies (Haukisalmi et al 2010a;Greiman and Tkach 2012) have corroborated this hypothesis and have demonstrated that the loss of the rostellum, or the rostellar armature, has occurred in several independent lineages of hymenolepidids among mammals. For example, this is exemplified by species of the Arostrilepis horrida complex (syn.…”

“…Access to new comparative materials for concurrent or integrated morphological/molecular analyses is essential to enhance our ability to more completely document parasite faunal diversity among Peromyscus spp. and other rodents (e.g., Haukisalmi et al 2010a;Makarikov et al 2013a, b). Deposition of specimens from inventories is a basic foundation for characterization of faunal structure (e.g., Hoberg et al 2009) and is increasingly necessary given the expanding recognition of cryptic diversity across many groups of parasites and hosts (Pérez-Ponce de León and Nadler 2010).…”

“…For example, this is exemplified by species of the Arostrilepis horrida complex (syn. : Hymenolepis horrida), which are not closely related to Hymenolepis (Haukisalmi et al 2010a), yet they lack a rostellum.…”

“…For example, among hymenolepidids, the genus Arostrilepis appears to be the sister of tapeworms among Soricomorpha with origins then attributable to host colonization of Arvicolinae (e.g., Haukisalmi et al 2010a); subsequent diversification reflects episodes of host colonization among geomyid and neotomine rodents (e.g., Makarikov et al 2012;Hoberg et al 2012). Considering H. folkertsi, morphological similarity among Nearctic species is observed for H. tualatinensis in a geomyid from central Oregon, H. pitymi in an arvicoline from Tennessee, and H. robertrauschi in species of Onychomys a related neotomine, and putative sister of Peromyscus, across west-central North America from southern Canada to northern Mexico.…”

Cryptic diversity in hymenolepidid tapeworms infecting humans

“…However, 43 molecular phylogenetic studies on interspecific and intergeneric relationships within 44 the family are still in their infancy [2]. Although a few members of the genus 45 Hymenolepis sensu lato are of medical importance as pathogenic organisms, their 46 taxonomy is still controversial, particularly that of Hymenolepis nana [2] …”