Comparative analysis of phenotypic variability of introduced land snail Cepaea nemoralis (Gastropoda: Helicidae) in two large Eastern European cities

Variation in the shell colour and banding polymorphism of Cepaea nemoralis was recorded in 20 sites in Minsk, Belarus (a total of 3965 adults collected in 2014–2021). This variation was compared with that in 16 sites from Lviv, Western Ukraine (total 3235 adults collected in 2019–2021). Unlike in Lviv, a remarkable spatial differentiation of the phenotypic composition was found in Minsk. The samples collected in the north-eastern part of Minsk were characterized by a greater degree of phenotypic diversity and by higher frequencies of unbanded and brown shells. Samples from the southern and eastern parts of the city were generally lighter and characterised by high frequencies of shells with a single central band (mid-banded). Differences between the two parts of Minsk were greater than those between Minsk and Lviv. This may be related to the history of colonization of Minsk by C. nemoralis. The Lviv samples were, on average, darker, they contained less frequently mid-banded shells and more frequently unbanded shells, especially pink unbanded ones. The Fst values characterizing the level of phenotypic variability and calculated for Minsk and Lviv are quite high and comparable with those for other urban areas recently colonized by C. nemoralis.