MOLECULAR PHYLOGENY OF THE GENUS ECHINOCOCCUS

Three nucleotide data sets, two mitochondrial (COI and ND1) and one nu clear (ribosomal ITS1), have been investigated in order to resolve rel ationships among species and strains of the genus Echinococcus. The da ta have some unusual properties in that mitochondrial heteroplasmy was detected in one strain of E. granulosus, and more than one class of I TS1 sequence variant can occur in a single isolate. The data failed to support the hypothesis that E. granulosus, as it is currently viewed, is a single valid species. Rather, the strains of E. granulosus seem to comprise at least three evolutionarily diverse groups, the sheep st rain group, bovine strain group and horse strain group. Molecular dist ances between them are comparable to, or greater than, molecular evolu tionary distances observed between recognized species. The affinities of the cervid strain of E. granulosus are unclear because of ambiguous data, but this strain does not appear to be ancestral to others. E. m ultilocularis may not be distinct from E. granulosus. However, the rem aining two species, E. vogeli and E. oligarthrus appear distinct and r ather distant from the first two. Based on the results presented here, taxonomic revision of the genus is clearly warranted.