Distribution of the Najas species in Lithuania (Hydrocharitaceae): Revised data from the 19th century onwards

Abstract The article presents data on the distribution of four Najas species in Lithuania, starting from the first records at the beginning of the 19th century. The work is based on a review of specimens stored in Lithuanian herbaria, paying special attention to the localities indicated on the labels or mentioned in publications. Najas marina and Najas major were first presented in Lithuania as separate species, occurring in different waterbodies. The wide distribution of these species and in several locations observed abundance, indicating that they do not require protection. However, monitoring of future distribution changes would be recommended due to possible invasiveness. The first known locality of Najas minor was corrected, based on information in herbarium labels and literature sources. Based on the acquired data, strict protection is still required for the rare species, Najas minor and particularly Najas flexilis, as the known localities in Lithuania are the southernmost extent of its distribution range. With minor exceptions, the distribution of all recorded Najas species within Lithuania is restricted to waterbodies in the Baltic Uplands, extending from the south to the northeast of the country.