RELATIONSHIPS AMONG PROBLEMATIC NORTH-AMERICAN STAGNICOLINE SNAILS (PULMONATA, LYMNAEIDAE) REINVESTIGATED USING NUCLEAR RIBOSOMAL-RNA INTERNAL TRANSCRIBED SPACER SEQUENCES

The taxonomic relationships among four stagnicoline snail species from North America were reassessed by analysing nucleotide sequences from their nuclear ribosomal internal transcribed spacer (ITS) region. Thre e of the species (Stagnicola catascopium, Stagnicola emarginata, and S tagnicola elodes) are representatives of the subgenus Stagnicola s.str . from the northern U.S.A. and the fourth is a closely related Canadia n species (Stagnicola caperata) belonging to the subgenus Hinkleyia. M embers of the two subgenera differed considerably in their ITS sequenc es, demonstrating the usefulness of these sequences for distinguishing species from closely related lymnaeid subgenera. In contrast, ITS seq uences for the three members of the subgenus Stagnicola s.str. were ve ry similar, which supports an earlier view that they may not be separa te species.