Since the last comprehensive overview of the Czech and Slovak mollusc fauna, released in 2013, several records of species new for the countries or particular regions have appeared. In this paper, we summarize all such records and news collected in 2015–2019, including those affecting nomenclature and the national Check-lists made in 2013 and 2014. The rules for the selection of the records are: (i) the first record in Bohemia, Moravia or Slovakia, (ii) regionally important new records, (iii) records of species listed in NATURA 2000 and the national Red-lists as either critically endangered or endangered species, and (iv) currently spreading non-native species. New records are briefly commented and summarized for each species separately. Location data are published with all details in a supplementary table and are freely accessible.

Sequences of mitochondrial genes revolutionized the understanding of animal diversity and continue to be an important tool in biodiversity research. In the tribe Helicini, a prominent group of the western Palaearctic land snail fauna, mitochondrial data accumulating since the 2000s helped to newly delimit genera, inform species-level taxonomy and reconstruct past range dynamics. We combined the published data with own unpublished sequences and provide a detailed overview of what they revealed about the diversity of the group. The delimitation of Helix is revised by placing Helix godetiana back in the genus and new synonymies are suggested within the genera Codringtonia and Helix. The spatial distribution of intraspecific mitochondrial lineages of several species is shown for the first time. Comparisons between species reveal considerable variation in distribution patterns of intraspecific lineages, from broad postglacial distributions to regions with a fine-scale pattern of allopatric lineage replacement. To provide a baseline for further research and information for anyone re-using the data, we thoroughly discuss the gaps in the current dataset, focusing on both taxonomic and geographic coverage. Thanks to the wealth of data already amassed and the relative ease with which they can be obtained, mitochondrial sequences remain an important source of information on intraspecific diversity over large areas and taxa.

Helix lucorum is a large synanthropic land snail of substantial economic importance, which has been recently reported from a number of new sites in Western, Central, and Eastern Europe. It is an originally Anatolian and Caucasian species, but its presumed natural distribution also covers the south and east of the Balkans. Populations of unclear origin, known as Helix lucorum taurica, live in the south-western part of Crimea. The Balkan and Crimean populations differ in their appearance, were long treated as different species or subspecies, and the Crimean populations are protected by law as a presumably endemic taxon. Here we explore the origins of European populations using phylogenetic analysis of mitochondrial markers. The results point to north-eastern Anatolia and the Lesser Caucasus as the centre of H. lucorum diversification. The Crimean conchological form, along with the associated mitochondrial lineage, is not endemic to that peninsula and was likely introduced there. Other European samples belong to a different lineage, which is associated with the nominotypical conchological form of H. lucorum. The conchological characteristics of the nominotypical form are unusual within the genus Helix, and we propose this reflects a change in habitat use and parallels the evolution of some other lineages of Helicidae. As a result, the typical European H. lucorum differs considerably from the Crimean populations, but the two lineages just represent opposite ends of a continuum in conchological characteristics. Their formal descriptions were based on probably introduced populations detached from the main range. Separated from the geographic pattern of the overall variation of H. lucorum they appeared distinctive, thus confounding the taxonomy of the species. Currently, the division of H. lucorum into subspecies appears unwarranted. Helix lucorum may not be a unique example of a large snail successfully expanding from Anatolia, as we argue that even the native origin of Balkan populations is uncertain. However, further sampling in north-western Turkey and analysis of archaeozoological findings from the south-eastern Balkans is needed to evaluate this hypothesis.

The Roman snail Helix pomatia Linnaeus, 1758 is a large terrestrial gastropod very common in central and southeastern Europe, and is the type species of the genus. A recent molecular phylogenetic study has uncovered two divergent lineages within the species as currently conceived. One represents the true H. pomatia, the second corresponds to a previously recognized subspecies H. pomatia thessalica Boettger, 1886. Using more samples, new molecular data and thorough morphological investigations, we redescribe the latter as a separate species. Morphological differences, especially colouration and surface sculpture of the shell and dark colouration of distal genitalia, distinguish this taxon reliably from H. pomatia. The species is widespread in the southern Balkans, but its range extends also to central Europe along the Carpathian Arc. Thus, its distribution broadly overlaps with that of H. pomatia and we have found evidence for occasional hybridization between the two species. Some lineages of H. thessalica seem to be restricted to the Carpathians and their vicinity; these might have survived locally during the last glacial. By clarifying the taxonomy of H. pomatia, we make the crucial first step towards elucidating the phylogeographic history of this iconic member of the European land snail fauna.