Evolutionary transitions in broad tapeworms (Cestoda: Diphyllobothriidea)

• Main Author: Natalia Fraija-Fernández, Andrea Waeschenbach, Andrew Briscoe, Suzanne Hocking, Roman Kuchta, Tommi Nyman, D. Timothy J. Littlewood
• Format: Dataset
• Language: English
• Published: Natural History Museum 2021
• Subjects: Brabec; Bray; Fennoscandian
• Online Access: https://dx.doi.org/10.5519/pe2kakcr; https://data.nhm.ac.uk/dataset/a2b5a2b0-722d-482e-9bf9-338b31dc2cf2

Broad tapeworms (Diphyllobothriidea Kuchta, Scholz, Brabec and Bray, 2008) are wildlife parasites whose adults are capable of infecting a wide range of freshwater, marine and terrestrial tetrapods. Previous works examining the evolution of habitat and host use in this group was hampered by the lack of a well-resolved phylogeny. In order to produce a robust phylogenetic framework for diphyllobothriideans, we sequenced the complete mitochondrial genomes of 13 representatives, carefully chosen to cover the major clades, and two outgroup species (Spathebothriidea and Haplobothriidea). In addition, complementary data from the nuclear ribosomal operon was sequenced for 10 representatives. Mitogenomes and ssrDNA and lsrDNA were used to produce the best-resolved phylogenetic framework for the Diphyllobothriidea to date. The Cephalochlamydidae is confirmed as the earliest diverging diphyllobothriidean lineage, and Solenophoridae and Diphyllobothriidae are sister groups. We infer a freshwater origin of the diphyllobothriideans with a two-host life cycle, in which amphibeans are the definitive host. The life cycle expanded to three hosts with the origin of the Solenophoridae and Diphyllobothriidae. Habitat use remained freshwater in the early diverging lineages in the Solenophoridae + Diphyllobothriidae clade, with Solenophoridae parasitising exclusively reptile definitive hosts. Habitat use of the Diphyllobothriidae shifts between freshwater and marine environments and definitive host use includes marine and terrestrial mammals and birds. Furthermore, we use complete mitochondrial genomes to distinguish Schistocephalus species occurring in different species of sticklebacks and to demonstrate conspecificity of Ligula intestinalis specimens collected from two Fennoscandian ringed seals subspecies.