Internal transcribed spacer rDNA can be used to infer the phylogenetic relationships of species within the genus Nematodirus (Nematoda : Molineoidea)

Sequences of the first internal transcribed spacer rDNA were characterised for four veterinary important species of gastrointestinal nematodes from th e genus Nematodirus. The sequence data were combined with previously publis hed data of the second internal transcribed spacer to determine whether the se rDNA regions provided a suitable number of informative characters to det ermine the phylogenetic relationships of species within the genus. A total of 32 alignment positions of the first internal transcribed spacer data set and 33 characters from the second internal transcribed spacer data set wer e informative in phylogenetic analyses. Irrespective of whether the data fr om each spacer were analysed separately or combined, only one most parsimon ious tree was produced, with the relationships of the four species fully re solved. In addition, several regions of conservatism in the first internal transcribed spacer sequence among the four Nematodirus species suggests tha t this rDNA region may also provide phylogenetic information for higher tax onomic levels within the Molineoidea. (C) 2000 Australian Society for Paras itology Inc. Published by Elsevier Science Ltd. All rights reserved.