Molecular Phylogeny and DNA Barcoding of the Narrowly Endemic Freshwater Snail Bithynia gonensis (Mollusca: Bithyniidae) from Türkiye

Objective: Bithynia gonensis D. A. Odabaşı, 2024 is a narrowly endemic freshwater snail restricted to the Gönen Stream in northwestern Türkiye. Despite the reported diversity of Bithyniidae in Türkiye, species identifications have largely relied on morphologic characteristics without molecular support. This study aimed to investigate the phylogenetic position of B. gonensis using mitochondrial COI barcode data.Materials and Methods: Specimens were collected from the type locality, and genomic DNA was extracted from foot tissue. A partial fragment of the mitochondrial cytochrome c oxidase subunit I gene was amplified using modified LCO/HCO primers. Sequences were aligned and analyzed in MEGA X, and phylogenetic relationships were inferred using the neighbor-joining method based on uncorrected p-distances with 1000 bootstrap replicates.Results: The analyses revealed that B. gonensis forms a distinct and well-supported monophyletic lineage. It appears as a sibling group to a clade comprising Bithynia sp. from Lake Eğirdir and B. zeta Glöer & Pešić, 2007, with moderate bootstrap support. The species shows clear genetic divergence from B. tentaculata and B. cettinensis.Conclusion: This study provides the first molecular data for a bithyniids species from Türkiye and supports the distinct taxonomic status of B. gonensis. The findings emphasize the importance of integrating molecular approaches into the taxonomy of Turkish freshwater gastropods.