Two instead of one: citizen science and range clarification of Helix thessalica and H. pomatia (Gastropoda: Helicidae) in Ukraine

Numerous observations by amateur naturalists, together with some literature data and the malacological collection of the State Museum of Natural History in Lviv, helped to clarify the present ranges of two large and similar land snails, which were previously considered to be one species, Helix pomatia. It has been confirmed that the true H. pomatia is widespread in Ukraine, both within its probable natural range and due to anthropochory. The known range of H. thessalica extends in a rather narrow strip from the west to the east of the country. In Western Ukraine, it avoids both the mountainous part of the Ukrainian Carpathians and many plain areas. It also avoids the mixed forest zone in the north of Ukraine and the steppe zone in the south. This paper completes a series of publications on the present distribution of Helix species in Ukraine.