A molecular systematic framework for equine strongyles based on ribosomal DNA sequence data

In this study, molecular data sets were used to address the controversies r elating to the systematics of strongyloid nematodes of equids utilising mor phological data sets. DNA sequences of the first and second internal transc ribed spacers (ITS-1 and ITS-2) of ribosomal DNA were determined for 30 spe cies of equine strongyles and the systematic relationships reconstructed us ing phenetic and phylogenetic tree-building methods. Thr molecular data pro vided support for the hypothesis that the genera with large subglobular buc cal capsules are ancestral to those with small cylindrical buccal capsules. but did not provide support for the current division of the subfamilies St rongylinae and Cyathostominae or for some taxonomic groupings (i.e. generic designations of species) within the Cyathostominea based on morphological data. Although not entirely concordant, the current molecular data provide a systematic framework for future studies of equine strongyles, which could be exploited in combination with new, phylogenetically informative morphol ogical data sets. (C) 2000 Australian Society for Parasitology Inc. Publish ed by Elsevier Science Ltd. All rights reserved.