First record of Nitellopsis obtusa (Characeae) in Mongolia: A novel genus in the national flora

Nitellopsis obtusa (Desv.) J.Groves, the species of charophytes (Characeae, Charales), has a wide distribution from Europe to Asia, and is listed as threatened species in certain countries. While 19 species of Chara , Nitella and Tolypella have been documented in Mongolia, N. obtusa has remained unreported. In this study, we provided the first documented occurrence of N. obtusa in Mongolia, specifically from the Khar-Us and Khar Lakes and the connecting Chono Kharaikh River (western Mongolia). Species identification was corroborated by morphological observations and molecular analysis. The majority of specimens examined were sterile, with only a limited number of thalli-bearing oogonia (female reproductive organs). This study presents a detailed account of the morphology, taxonomy, phylogeny, and geographical distribution of N. obtusa in Mongolia.