Phylogenetic analysis of the suborder Plagiorchiata (Platyhelminthes, Digenea) based on partial lsrDNA sequences

The phylogenetic relationships and systematic position of the members of th e suborder Plagiorchiata, one of the derived and most diverse groups of Dig enea, have always been controversial. Here, we present a phylogeny of this group based on the analysis of partial sequences of the 1srDNA in 28 specie s representing 13 families of Plagiorchiata, as well as four outgroups. Our results show that the Plagiorchiata, as considered by most authors, is not monophyletic, and that the superfamilies Opecoeloidea, and most probably D icrocoelioidea and Gorgoderoidea, may have to be removed from this suborder . According to our results, the Plagiorchiata includes only parasites of te rrestrial vertebrates. We find the Plagiorchiata to be composed of two well -supported clades which can be ranked as superfamilies: (1) Plagiorchioidea , including the Plagiorchiidae, Haematoloechidae, Telorchiidae, Brachycoeli idae and Leptophallidae: and (2) Microphalloidea containing the Microphalli dae, Prosthogonimidae, Lecithodendriidae and Pleurogenidae. The genetic ana lysis also allowed revision of the position of several taxa of Plagiorchiat a, including: (1) a confirmation of the position of the Brachycoeliidae wit hin the Plagiorchiata; (2) a close phylogenetic relationships of Macrodera with Paralepoderma, Leptophallus and Metaleptophallus; (3) the grouping of Opisthioglyphe and Telorchis within a distinct and strongly supported clads ; and (4) the placement of Allassogonoporus amphoraeformis within the Pleur ogenidae, and not close to Lecithodendriidae. Some systematic changes, corr esponding to these results, are proposed. (C) 2000 Australian Society for P arasitology Inc. Published by Elsevier Science Ltd. All rights reserved.