Molecular and Biochemical Parasitology 90 (1997) 433 – 438 Phylogenetic analysis of the Monogenea and their relationships with Digenea and Eucestoda inferred from 28S rDNA sequences 1 Isabelle Mollaret a , Barrie G.M. Jamieson b , Robert D. Adlard c , Andrew Hugall b , Guillaume Lecointre d , Catherine Chombard d , Jean-Lou Justine a, * a Laboratoire de Biologie Parasitaire, Protistologie, Helminthologie, ERS 156 CNRS, Muse ´um National d’Histoire Naturelle, 61 rue Buffon, F -75231 Paris cedex 05, France b Zoology Department, Uniersity of Queensland, Brisbane 4072, Queensland, Australia c Queensland Museum, PO Box 3300, South Brisbane 4101, Queensland, Australia d Serice de Syste ´matique Mole ´culaire, CNRS (GDR 1005), Muse ´um National d’Histoire Naturelle, 43 rue Cuier, 75231 Paris cedex 05, France Received 14 August 1997; received in revised form 25 September 1997; accepted 3 October 1997 Abstract Platyhelminth phylogeny is controversial. Phylogenetic analyses of the partial domain C1 and the full domains D1 and C2 (358 nucleotides) from the 28S ribosomal RNA gene for 21 species from the Monogenea, Digenea, Cestoda, and, as the outgroup, Tricladida reveal major departures from prevailing theory. The Digenea and not the Monogenea (Monopisthocotylea and Polyopisthocotylea) form the sister group of the cestodes; the Monopisthocotylea and Polyopisthocotylea are each monophyletic, but the Monogenea do not form a monophylum; the sister group of the Digenea +Cestoda is the Polyopisthocotylea; and Monopisthocotylea are the sister group of all other parasitic flatworms. © 1997 Elsevier Science B.V. Keywords: Monogenea; 28S DNA; Phylogenetic analysis 1. Introduction The Platyhelminthes (flatworms) are presently the center of a discussion on the origin of the Metazoa [1,2]. Among the Platyhelminthes, the parasitic flatworms (flukes and tapeworms), which Abbreiations: PCR, polymerase chain reaction. * Corresponding author. Tel.: +33 1 40793503; fax: +33 1 40793499; e-mail: justine@mnhn.fr 1 Note: Nucleotide sequence data reported in this paper are available in the EMBL, GenBank™ and DDJB data bases under the accession numbers AF026103 – AF026119. 0166-6851/97/$17.00 © 1997 Elsevier Science B.V. All rights reserved. PII S0166-6851(97)00176-X