Different introductions and the spread of Cepaea hortensis (Gastropoda: Helicidae) across Ukraine: new data and an impetus for further research

This paper analyses the results of our own long-term research from 1998 to 2025, as well as other available data on the colouration of the shell, shell lip and body in C. hortensis from different parts of Ukraine (in total, more than a hundred settlements from 18 administrative regions). Quantitative samples were collected in 55 cities and smaller settlements, and less frequently in their immediate surroundings, in the west of the country. A map of known C. hortensis finds in Ukraine has been compiled, taking into account the recorded variants of its colouration, some of which can serve as phenotypic markers of different “waves” of C. hortensis introduction to Ukraine. It has been established that the descendants of the primary introduction of C. hortensis to Western Ukraine (second half of the 20th century) are now widespread across the Lviv region and are reliably found in the Ivano-Frankivsk, Ternopil, and Volyn regions. Signs of later secondary introductions through garden centres (not earlier than the very end of the 20th or the beginning of the 21st century) began to be discovered in Ukraine quite recently, since 2015. Currently, they are known for 9 administrative regions: in the west (Lviv, Ivano-Frankivsk, Ternopil, Rivne, Transcarpathian), in the centre (Kyiv, Zhytomyr, Kirovohrad) and in the east (Kharkiv) of Ukraine. Mixed populations formed by descendants of primary and secondary introductions have been found so far mainly in the Lviv region. The possible influence of climatic selection on the phenotypic composition in Western Ukrainian populations of C. hortensis, which have different origins, as well as the perspectives for further research of the colouration polymorphism in this species from different parts of Ukraine are discussed.