Schoenoplectus is a morphologically diverse genus that contains 30-40 species that is found predominantly in wetland areas. The genus has a complex taxonomic history and was previously considered a segregate of Scirpus. Recent molecular analysis by Muasya et al. (2000) using trnL-F and rbcL has shown evidence of paraphyly in Schoenoplectus, but a comprehensive phylogenetic analysis of this genus has not been undertaken. This study attempts to clarify relationships within the North American species by using ITS DNA sequence data. Fourteen ingroup and two outgroup taxa were examined in this preliminary study using maximum parsimony. Schoenoplectus, as currently delimited, is paraphyletic. Isolepis is sister to the dwarf species of Schoenoplectus, and three sampled species that were formerly placed in Bolboschoenus are sister to the Isolepis-Schoenoplectus clade. In our preliminary analysis there are indications that the large-sized Schoenoplectus species form a monophyletic group. Expanded sampling within Schoenoplectus and related genera is in progress.

Key words: Cyperaceae, Schoenoplectus, Scirpus, systematics