SHORT COMMUNICATION F. Audebert Æ N. Chilton Æ J.-L. Justine Æ C. Gallut A. Tillier Æ M.-C. Durette-Desset Additional molecular evidence to support a sister taxon relationship between Heligmosomoidea and Molineoidea nematodes (Trichostrongylina) Received: 1 March 2005 / Accepted: 15 April 2005 / Published online: 28 May 2005 Ó Springer-Verlag 2005 Abstract Sequences of the first and second internal transcribed spacers of the ribosomal DNA were used to infer the evolutionary relationships of 19 species of parasitic nematode belonging to three superfamilies, Trichostrongyloidea, Molineoidea and Heligmosomoi- dea, within the sub-order Trichostrongylina. Analyses using maximum parsimony, maximum likelihood and neighbor-joining methods revealed strong statistical support for monophyly of each superfamily as defined on morphological criteria. Furthermore, in most analy- ses, there was also strong support for a sister taxon relationship between the Molineoidea and Heligmoso- moidea, which supports the findings of a previous study based on partial LSU rDNA sequence data. Introduction Trichostrongyloid nematodes represent one of the most species-rich groups of bursate nematode (order Strong- ylida). They occur principally in the gastrointestinal tracts, except for some species in the respiratory tract, of many groups of terrestrial vertebrates (Chabaud 1974; Durette-Desset 1985). It was proposed by Durette-Des- set (1985) that the trichostrongyloids comprised three major evolutionary lineages (trichostrongylids, moline- ids and heligmosomids) based on their morphological and biological characteristics, the range of hosts they used and on biogeographical and paleobiogeographic information pertaining to their hosts. Each lineage was designated family status within the superfamily Tricho- strongyloidea. However, elevation of the Tricho- strongyloidea to subordinal status by Durette-Desset and Chabaud (1993) resulted in each lineage of tricho- strongyloid nematode also being raised to superfamily status (i.e., Trichostrongyloidea, Molineoidea and He- ligmosomoidea) within the newly created suborder Trichostrongylina. The evolutionary relationships of these three superfamilies within the Trichostrongylina based on morphological characteristics have never been postulated because of a lack of cladistically informative characters (Durette-Desset et al. 1994). Gouy¨ de Bellocq et al. (2001) therefore conducted a molecular phylogenetic study to infer relationships within the Trichostrongylina using sequence data of the D1-D2 domain of the large subunit (LSU) ribosomal (r) DNA. They found that each lineage (i.e., superfamily) of trichostrongyloid nematode represented a monophyletic assemblage and that there was a sister taxon relationship between the Heligmosomoidea and Molineoidea. The latter result was not suspected, based on previous mor- phological analyses (Chabaud 1974; Durette-Desset et al. 1994), because the Trichostrongyloidea and Mo- lineoidea share some morphological features, such as a simple synlophe with bilateral symmetry (when a synl- ophe is present) and a didelphic female genital apparatus F. Audebert Æ J.-L. Justine Æ M.-C. Durette-Desset De´partement Syste´matique et Evolution, Museum national d’Histoire naturelle, UMR 7138 associe´e au CNRS, BP 52, 61, rue Buffon, 75231 Paris Cedex 05, France Present address: J.-L. Justine Equipe Bioge´ographie Marine et Tropicale, Unite´ de Syste´matique, Adaptation, Evolution (CNRS, UPMC, MNHN, IRD), Institut de Recherche pour le de´veloppement, BP A5, 98848 Noume´a Cedex, New Caledonia F. Audebert (&) Æ C. Gallut Laboratoire Informatique et Syste´matique, Universite´ Pierre et Marie Curie, UMR 5143 associe´e au CNRS, 12, rue Cuvier, 75005 Paris, France E-mail: fabienne.audebert@snv.jussieu.fr Tel.: +33-1-44274827 Fax: +33-1-44276560 N. Chilton Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, SK, S7N 5E2, Canada A. Tillier Service de Syste´matique mole´culaire, Institut de Syste´matique (CNRS 1541), Muse´um national d’Histoire naturelle, 43, rue Cuvier, 75231 Paris Cedex 05, France Parasitol Res (2005) 96: 343–346 DOI 10.1007/s00436-005-1402-y