Harmozica ravergiensis (Gastropoda: Hygromiidae) in Western Ukraine as part of anthropogenic expansion of its range

Abstract

In September 2023, a large population of the Caucasian snail Harmozica ravergiensis was discovered in a newly built residential complex in Lviv. This is its second record in Western Ukraine, with an interval of almost 20 years, as well as the westernmost known locality of the species. Adults of H. ravergiensis from Lviv had larger shells compared to samples from other introduced Eastern European populations of this species, measured by us personally or described in the literature. Another 16 species of land molluscs, mostly alien to Ukraine or its western part, were found in Lviv together with H. ravergiensis. The latter includes a snail of Crimean origin, Monacha fruticola, which is still rarely recorded north of the steppe zone of Ukraine. In the studied area of Lviv, H. ravergiensis and M. fruticola often formed joint aggregations, which had never been observed before in Ukraine. Possible ways of penetration of H. ravergiensis and some other introduced molluscs into the studied area are discussed. Now H. ravergiensis is most often found in Eastern Ukraine, especially in the Donetsk region (the earliest known record dates back to 1990). There are also a few reliable finds in Western (since 2006) and Central (since 2015) Ukraine. In general, in the late 20th and early 21st centuries, the range of H. ravergiensis expanded significantly, reaching the Tver region of Russia in the north, the southern Ural in the northeast, Central Asia in the southeast, and Western Ukraine in the west. Here, we analyse for the first time the extent of this expansion based on personally studied material, published data, and images in two citizen science databases.