Leuciscus is a genus of fish belonging to subfamily Leuciscinae. While, it is widely distributed throughout Eurasia, our perception of the phylogenetic relationships among its members is mainly based on morphological characters. In this study, two mitochon-drial (CYTB and COX1) and one nuclear (RAG1) genomic mark-ers were used in order to assess the taxonomic relationships be-tween two Iranian Leuciscus morpho-species. Analysis of the combined dataset using Maximum Likelihood (ML) and Bayes-ian Inference (BI) approaches resulted in well-resolved trees, where most clades were supported by high statistical values. The trees revealed two clades corresponding with the Caspian Asp, Leuciscus aspius, and the Mesopotamian Asp, L. vorax. species The mean intraspecific and interspecific genetic distance between Leuciscus species was 0.5% and 10.6%, respectively. The genetic distance between L. aspius sequences of Iran and Europe was 1.1% and the genetic distance between L. vorax sequences from Iran and those of Turkey and Syria was 0.8%. This confirmed that the morpho-species Leuciscus from the Caspian basin belongs to L. aspius species, while those from the Tigris basin belong to L. vorax species. Due to very small genetic distances between some Leuciscus members, specific species delimitation analysis are required to clarify genus taxonomy throughout Leu-ciscus distribution range.

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