Nuclear rDNA ITS sequence variation in the trematode genus Echinostoma: An aid to establishing relationships within the 37-collar-spine group

The taxonomic history of members of the 37-collar-spine group within the genus Echinostoma has been very confused. We obtained DNA sequence data from the nuclear rDNA ITS1, 5.8S and ITS2 of 7 nominal species belonging to this group, Echinostoma trivolvis (Cert, 1914), E. revolutum (Frolich, 1802), E. caproni Richard, 1964, E. acaproni arasasingam et nl. 1952, E. paraelzsei Lie & Basch, 1967, two African isolates, E. sp.I and E. sp.II, and of one 28-collar-spined echinostome, E. holtense (,4sada, 1926). Five of the eight species n;ere clearly distinguishable using ITS data. Sequences from the remaining three tasa, E. cnpl olzi, E. sp.ll and E. liel mere identical to one another and the group containing these laxa was distant from other 3'7-collar-spine species on a phylogenetic tree. E. tvizrolzris and E. pavaensei form a second, but less distinct group within the 35-collar-spine group. The resolution obtained using DNA sequencing will assist in the current reclassification of the group. It also provides a model for future work on sibling species