Background and Aims: The genus Sium comprises hydrophytic herbs. There are 11 species mainly distributed in Euroasia and North America. In Trkiye, it is represented only by S. sisarum. However, a suspicious specimen collected by Davis from Hakkari suggested that S. latifolium may also exist. This specimen resembled S. latifolium with its slightly grooved stem and dimorphic leaves but also S. sisarum with its very short calyx lobes. Morphological examinations were not sufficient to identify the specimen. Therefore, the aim of this study was to clarify whether S. latifolium is present in Trkiye using phylogenetic methods.
