First Molecular Identification and Phylogenetic Analysis of Three Unio Species (Bivalvia: Unionidae) from the Kurdistan Region, Iraq

Unionidae Freshwater mussels are ecologically significant but little is known about them at a molecular level in Iraq. In this work, two freshwater sites of a lake close to Hizop River and the Greater Zab River close to Qandil village, Erbil Governorate, Kurdistan Region, Iraq were sampled from April to June 2025 and bivalves were collected. Morphological analysis with cytochrome oxidase subunit I (COI) sequence analysis of the mitochondrial genome was used to identify the species. Molecular studies indicated that the specimens were Unio pictorum (Linnaeus, 1758), Unio bruguierianus Bourguignat, 1853 and Unio tumidus Philipsson, 1788, with sequence similarity (99.8 to 100) to reference sequences that are available in GenBank. Neighbor-Joining, Maximum Likelihood and Bayesian Inference analyses provided phylogenetic support and well-supported clades with the highest bootstrap percentage (100%), thereby supporting the location of all three species in genus Unio (family Unionidae). The obtained COI sequences were deposited to NCBI GenBank database. Unio pictorum and Unio tumidus are the first reported in Iraq on both morphological and molecular evidence, and neither of the species has been recorded in the country before. Unio bruguierianus, the species which was previously known in Iraq only morphologically as Unio ciconius Kobelt, 1913, a name which has been synonymised in the U. crassus complex, is proven a separate species and described with the first molecular evidence. All these findings constitute the earliest morphological and molecular record of U. pictorum and U. tumidus in Iraq, and the earliest molecular record of U. bruguierianus in the Iraq. These findings are applicable to the distributions of all three species into the upper Tigris basin and will provide useful baseline information in future biodiversity studies and conservation strategies of freshwater mussels in the Kurdistan Region and Iraq.