The interrelationships of all major groups of Platyhelminthes: phylogenetic evidence from morphology and molecules

Abstract

We used a data matrix of 65 morphological characters from 25 ingroup and 6 outgroup taxa, and an alignmcnt comprising complete 18s rDNA scqucnccs from 82 species of parasitic and free-living Platylielminthcs and from 19 species of loivcr invcrtchratcs to analyse phylogenctic relationships ofvarious platyhclminth taxa. Of the 1358 unambiguously aligiiablc molecular positions, 995 wcrc variable and 757 \vcrc phylogcnetically informative (parsimony criterion); complete 18s rDNA sequences ranged in length from 1755 to 2873 lip. Main conclusions arc: Ncodermata are monophyletic, and the Trematoda, hlonogcnca and Cestoda within thcm arc monophylctic as well. The sister group of thc Ncodcrmata is all the otlicr Ncoophora; the Kalyptorhynchia, 'I'yphloplanida, Dalyclliida and Tcmiiocephalida form one clade, and the last three another. Rlonophyly of the Seriata is rejected, but Polycladida/ Rfacrostomida/Haplopharyngida arc monophylctic, as arc the last two taxa. As a consequence, validity of the taxon Trepaxonemata is rejected. Further studies must show the corrcct position of the Acoela and Ncmcrtodermatida. It is strcsscd that morphological and molecular data in some respects lead to contradictory results, for instance concerning the position of the Fccampiidac/ 1 ~r a . r t o n i n / Z~i i t /~~o~h~~~ and the rclativc position of the Lccithoepitlicliata. Denser sampling of taxa for molecular data, complcmcntary scqucnccs from independent gcncs, and inclusion of additional morphological data arc necessary to resolve thcsc contradictions. 0 1:)w 'l'l1r l . i l l 1 l~~~~l Socict) 01 1.011d011

Ultrastructural characteristics of the uterine epithelium of aspidogastrean and digenean trematodes

“…Recent morphological and molecular data suggest that the Aspidogastrea may be the sister group to the Digenea and that these together form the Trematoda. However, a conflicting view exists regarding the Aspidogastrea as a distinct group and distant from the Trematoda (Littlewood et al 1999, Roberts and Janovy 2005, Timofeeva 2005). Therefore, a search for additional characters is pertinent to our understanding of the phylogeny of these flatworms.…”

“…The aspidogastrean anatomy is similar to that of digeneans, whereas some aspects of its biology closer resemble that of the Monogenea (Roberts and Janovy 2005). Molecular data suggest a placement of the Aspidogastrea as the sister group of the Digenea (Littlewood et al 1999).…”

Platyhelminth systematics and the emergence of new characters

“…major lineages within the phylum; principally Ehlers (1985), but see also Littlewood et al (1999) and Zamparo et al (2001). Ehlers' scheme of classification, which built on an accumulation of characters from a diversity of sources was the first to be based on cladistics.…”

“…Each of these new hypotheses rejects previous morphological assessments, and although few morphological synapomorphies supported (Trematoda (Cestoda, Monogenea)) as suggested by Ehlers (1985), instability amongst molecular estimates have not promoted wide acceptance of any single molecular scenario. Meanwhile, the identity of the sister group to the Neodermata appears to be a large clade comprised of (Prolecithophora + Tricladida + (Genostomatidae + Fecampiida + Urastomidae)) (Littlewood et al, 1999), a clade subsequently named the Adiaphanida by Norén & Jondelius (2002); this scenario has been established primarily with ribosomal genes and requires further sampling of genes ( Fig. 1).…”

Parasite systematics in the 21st century: opportunities and obstacles

“…There is room for optimism, information about phylogenetic systematic methods in parasitology is being disseminated more widely (e.g., Pérez-Ponce de León 1997, Pérez Ponce de ) phylogenetic trees are being produced at a more rapid, there is an increased breadth of taxa being investigated, including those of general conceptual interest to evolutionary bi-ologists, and we are finally beginning to build a large enough database to compare the outcomes of analyses based upon morphological and molecular data. These results are encouraging because, when the data are subjected to rigorous phylogenetic analysis, they generally tend to produce congruent trees (e.g, Hoberg et al in press, Leon-Regagnon et al 1999, Nadler & Hudspeth 2000, although it make take some time for such agreement to be apparent and accepted (see e.g., Brooks et al 1985, Brooks 1989a,b, Brooks & McLennan 1993, Zamparo et al in press, Baverstock et al 1991, Blair 1993, Rohde et al 1993, Littlewood et al 1999.…”