Radix ampla (Hartmann, 1821) is a widely distributed Palaearctic freshwater snail with a still insufficiently known distribution. This work aims to improve the knowledge of the intraspecific variability in the most important characters
used for its determination. To find out which characters are really suitable to distinguish this species from other similar Radix species, an integrative approach was applied, involving morphological and molecular data (including sequences from six outgroup Radix species). Molecular sequences of the nuclear spacer fragment ITS-2 and the mitochondrial gene fragment cyt–b were obtained from 30 individuals of R. ampla as well as from eight individuals of R. monnardi (Hartmann, 1841) from different regions of Europe and Western Siberia. From the subsample of 36 specimens the variability of several characters that are commonly used for species identification (shell morphology, mantle pigmentation, shape and position of the bursa copulatrix, length and position of the bursa duct, length ratio of praeputium to penial sheath) were found to be broader than recognised in current literature. The differentiation of atypical R. ampla from R. balthica (Linnaeus, 1758) and R. lagotis (Schrank, 1803) using morphological characters only, was very difficult. R. monnardi and R. hartmanni (Hartmann, 1821) proved to be junior synonyms of R. ampla.