Lemna aequinoctialis migrates further into temperate continental Europe—A new alien aquatic plant for Ukraine

The article presents the results of studies of a series of species identifications of the genus Lemna (Lemnaceae) conducted in 2019. Duckweed samples were taken from eight localities in the northern regions of Ukraine and identified to species using morphological and molecular markers (barcoding). A new alien species of duckweed for Ukraine—lesser duckweed (Lemna aequinoctialis Welw.)—was discovered, to which this study is devoted. All other samples belonged to Lemna minor. The article presents the most complete description of the distribution of L. aequinoctialis Welw. in Europe, and also contains updated data on the species distribution of duckweeds in Ukraine. Six species of the genus Lemna are now known in Ukraine—three native and three alien. The ecological requirements of L. aequinoctialis are similar to those of L. minor. We examined the morphological similarities and differences between these species, and confirmed the results by molecular barcoding using the plastid regions of the atpF-atpH and psbK-psbI intergenic spacers.