INTRASPECIFIC VARIATION IN THE RDNA ITS LOCI OF 37-COLLAR-SPINED ECHINOSTOMES FROM NORTH-AMERICA - IMPLICATIONS FOR SEQUENCE-BASED DIAGNOSES AND PHYLOGENETICS

The recent finding of the 37-collar-spined Echinostoma revolutum in No rth America prompted rDNA nucleotide sequence comparisons between this worm and the sympatric Echinostoma trivolvis. Three isolates of E. re volutum from distinct sites and 2 isolates of E. trivolvis collected f rom a single site were used in this analysis. Sequence data were compa red to those from previously sequenced members of the 37-collar-spine group. The 3 North American isolates of E. revolutum were found to be identical, but they differed from Eurasian isolates of E. revolutum at 9 of the 1,006 sites sequenced. Further, 1 of the E. trivolvis isolat es studied herein was identical to the published sequence for this spe cies, but 6 nucleotide changes were observed in the second E. trivolvi s isolate. Restriction fragment length polymorphisms at this locus sup port the nucleotide differences found between the E. trivolvis isolate s. The degree of intraspecific variation detected raises questions reg arding the utility of the internal-transcribed spacer regions of the r ibosomal DNA repeat for taxonomic diagnosis and in phylogenetic studie s for poorly differentiated groups, such as the 37-collar-spined conge ners.