Throughout most of its range, there are no significant taxonomic issues associated with this name. However on the southern border of its distribution its taxonomy is less clear (Wiegleb and Kaplan 1998). The ecotype with oblong-lanceolate, 30-40 cm long leaves growing in some rivers in the European part of Russia and Russian Central Asia has been treated as an independent species; Potamogeton longifolius J. Gay. In the southern regions of European Russia smaller forms of P. lucens are found which resemble P. sarmaticus (Tzvelev 2001). Potamogeton lucens has been shown to hybridise with P. alpinus (P. xnerviger Wolfg. in Schult. et Schult.), P. crispus (P. xcadburyae Dandy et G. Taylor), P. gramineus (P. xangustifolius J. Presl in Bercht. et J. Presl), P. natans (P. xfluitans Roth) and P. perfoliatus (P. xsalicifolius Wolfg. in Schult. et Schult.). Of these, P. xsalicifolius is relatively widespread but usually occurs with one or both parents whereas P. xangustifolius is also widespread but is one of the few Potamogeton hybrids which often produces fertile seed and frequently occurs in the absence of both parents. It is possible that these hybrids could obscure the true distribution of P. lucens, but unlikely that they represent a threat to its survival.