Background and Aims: The genus Sium comprises hydrophytic herbs. There are 11 species mainly distributed in Euroasia and North America. In Türkiye, 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 Türkiye using phylogenetic methods.
Methods: All internal transcribed spacer DNA sequences of the genus Sium in GenBank that have been studied to date, including Davis’s specimen, were extracted. The dataset was phylogenetically analysed using both maximum likelihood and Bayesian inference.
Results: Sium species have mostly formed monophyletic lineages. Davis’s specimen was nested in one of these genera, and the S. latifolium, S. sisarum and S. latifolium subclades were located in different clades in the genus Sium.
Conclusion: The phylogenetic studies confirmed that the suspected Sium population collected in Hakkari was S. latifolium. Thus, it was phylogenetically proven that S. latifolium is distributed in Türkiye. Morpho logically, the presence of the submerged leaves and having a grooved stem, even if only slightly, were found to be important characteristics distinguishing it from S. sisarum.