DNA Barcoding of the Synodus randalli Cressey, 1981, from Iskenderun Bay, Eastern Mediterranean, Türkiye

The Indo-Pacific lizardfish Synodus randalli has entered the Mediterranean Sea via the Suez Canal and has rapidly expanded its range since it was first recorded in 2023. In this study, ten S. randalli specimens collected from the Iskenderun Bay (Türkiye) were genetically characterized using the COI barcode region. Phylogenetic analyses revealed that all Mediterranean S. randalli sequences form a highly supported monophyletic clade, clearly distinct from S. synodus and other species. Pairwise K2P distances indicated a distinct barcoding difference between S. randalli and S. synodus. Density plots, histograms, and box plots confirmed that intra- and inter-species variation ranges did not completely overlap. ASAP species delimitation analysis yielded two well-defined clusters corresponding to the two species. Overall, our results provide the first robust COI reference sequences for Mediterranean S. randalli, confirm its genetic distinctiveness, and demonstrate the reliability of COI barcodes for tracking non-native Synodontidae in the rapidly warming Mediterranean Sea.