A COI barcode reference dataset for Polish land gastropods supports biodiversity monitoring in Central Europe

Terrestrial molluscs are important components of terrestrial ecosystems, yet they remain poorly represented in molecular biodiversity assessments. Although they occur in a wide range of habitats, their inclusion in such studies is constrained by the lack of reliable genetic reference data, particularly in Central Europe. In Poland, despite a well-documented malacofauna comprising approximately 179 species, genetic data remain scarce. At the beginning of our study, 43 species lacked COI sequences in public repositories, while COI sequences from Polish specimens were available for only 11 species. Here, we present the first comprehensive COI DNA barcode reference dataset for Polish land gastropods, supported by expert morphological identification. We analysed 857 sequences representing 177 species occurring in Central Europe, including 21 species not yet recorded from Poland. The BIN approach yielded 291 molecular operational taxonomic units, 105 of which were unique to our dataset. Among putative species represented by at least five sequences, 83% exhibited a barcode gap, although its position varied considerably among the infraorder-level groups. For example, it occurred at approximately 11–20% K2P divergence in Clausilioidei and 5–10% in Limacoidei. This barcode reference dataset provides a valuable resource for land-gastropod identification and DNA-based biodiversity monitoring in Central Europe, including the detection of non-native species and lineages warranting further taxonomic investigation.