title: Orders out of chaos--molecular phylogenetics reveals the complexity of shark and stingray tapeworm relationships.
abstract: Novel molecular data are presented to resolve the long-standing issue of the non-monophyly of the elasmobranch-hosted tapeworm order Tetraphyllidea relative to the other acetabulate eucestode orders. Bayesian inference analyses of various combinations of full ssrDNA, and full or partial lsrDNA (D1-D3), sequence data, which included 134 species representing 97 genera across the 15 eucestode orders, were conducted. New ssrDNA data were generated for 82 species, partial lsrDNA data for 53 species, and full lsrDNA data for 29 species. The monophyly of each of the elasmobranch-hosted orders Cathetocephalidea, Litobothriidea, Lecanicephalidea and Rhinebothriidea was confirmed, as was the non-monophyly of the Tetraphyllidea. Two relatively stable groups of tetraphyllidean taxa emerged and are hereby designated as new orders. The Onchoproteocephalidea n. ord. is established to recognise the integrated nature of one undescribed and 10 described genera of hook-bearing tetraphyllideans, previously placed in the family Onchobothriidae, with the members of the order Proteocephalidea. The Phyllobothriidea n. ord. is established for a subset of 12 non-hooked genera characterised by scoleces bearing four bothridia each with an anterior accessory sucker; most parasitise sharks and have been assigned to the Phyllobothriidae at one time or another. Tentative ordinal placements are suggested for eight additional genera; placements for the remaining tetraphyllidean genera have not yet emerged. We propose that these 17 genera remain in the "Tetraphyllidea". Among these, particularly labile across analyses were Anthobothrium, Megalonchos, Carpobothrium, Calliobothrium and Caulobothrium. The unique association of Chimaerocestus with holocephalans, rather than with elasmobranchs, appears to represent a host-switching event. Both of the non-elasmobranch hosted clades of acetabulate cestodes (i.e. Proteocephalidea and Cyclophyllidea and their kin) appear to have had their origins with elasmobranch cestodes. Across analyses, the sister group to the clade of "terrestrial" cestode orders was found to be an elasmobranch-hosted genus, as was the sister to the freshwater fish- and tetrapod-hosted Proteocephalidea. Whilst further data are required to resolve outstanding nomenclatural and phylogenetic issues, the present analyses contribute significantly to an understanding of the evolutionary radiation of the entire Cestoda. Clearly, elasmobranch tapeworms comprise the backbone of cestode phylogeny.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Connecticut, 75 N. Eagleville Rd., Storrs, CT 06269-3043, USA. Electronic address: janine.caira@uconn.edu.
authors.forename: Janine N
authors.initials: JN
authors.lastname: Caira
authors.affiliation: Department of Ecology & Evolutionary Biology and the Biodiversity Institute, University of Kansas, 1200 Sunnyside Ave., Lawrence, KS 66045, USA.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Jensen
authors.affiliation: Department of Life Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK.
authors.forename: Andrea
authors.initials: A
authors.lastname: Waeschenbach
authors.affiliation: Department of Life Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Olson
authors.affiliation: Department of Life Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, UK.
authors.forename: D Timothy J
authors.initials: DT
authors.lastname: Littlewood
mesh_terms: D000818:Animals; D002589:Cestoda / Q000033:anatomy & histology / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D002590:Cestode Infections / Q000469:parasitology / Q000662:veterinary; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics*; D018940:Elasmobranchii / Q000469:parasitology*; D005393:Fish Diseases / Q000469:parasitology; D008969:Molecular Sequence Data; D012335:RNA, Ribosomal / Q000235:genetics*; D012337:RNA, Ribosomal, 18S / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D004275:DNA, Ribosomal; D012335:RNA, Ribosomal; D012337:RNA, Ribosomal, 18S; C065096:RNA, ribosomal, 26S
keywords: Cestoda; Elasmobranchs; New orders; Onchoproteocephalidea; Phyllobothriidea; Tetraphyllidea; lsrDNA; ssrDNA