Molecular taxonomy of the alpine bullhead Alpinocottus poecilopus (Heckel, 1837) from the Pomeranian enclave

The alpine bullhead ( Alpinocottus poecilopus ) is a cold-water benthic fish with a disjunct distribution across Europe, including a recently discovered population in northern Poland's Pomeranian region. Prior to now, the taxonomic identity of this enclave population has not been confirmed using molecular methods. This study presents the first DNA barcoding analysis of the A. poecilopus from Pomerania. Sequences of the mitochondrial coI gene and phylogenetic reconstruction confirmed the species identity and revealed no, or a very low genetic divergence between the Pomeranian and the Scandinavian and Czech Republic A. poecilopus . The results also support the recent reclassification of A. poecilopus into the genus Alpinocottus , alongside A. volki and A. szanaga , forming a distinct clade with C. kolymensis , which may also belong to this genus. These findings confirm that the Pomeranian alpine bullhead represents a genetically valid relict population, which was likely preserved due to postglacial isolation and specific cold-water habitat conditions. Additionally, unverified reports of an alpine bullhead occurrence in the Drwęca River basin (Vistula system) were clarified, as specimens from this site were identified as the European bullhead ( Cottus gobio ).