The genus Alburnoides belongs to the Cyprinidae family. This genus has long been considered as a complex species with great diversity in Iran. Six species were recently recognized in the Iranian basins of the Caspian Sea, Kavir Namak, Tigris, Kor, and Lake Orumiyeh incluing A. eichwaldii, A. namaki, A. idignensis, A. nicolausi, A. qanati and A. petrubanarescui, respectively, and more are expected to be discovered. In the present study the morphological and molecular variations among these species have been investigated. To study the morphological characteristic, 22 morphometric and nine meristic characters of 144 specimens of these six species were used. All measurements were recorded using a digital caliper to the nearest 0.01mm. Nine meristic characters were counted under a binocular microscope. For the molecular study, sequences of cytochrome b mitochondrial gene (409 bp) from the six species were analyzed (three specimens of each species, 18 PCR products in total). The results of morphological data showed a high similarity among the species, but could separate A. nicolausi and A. idignensis according to the first component and A. idignensis and A. petrubanarescui according to the second component in the principal component analysis. Moreover, based on the meristic characters which were relatively similar, again A. nicolausi and A. idignensis could be separated by the first component. Alburnoides eichwaldii was distinct from other species in the second component. The results of molecular analysis showed A. eichwaldii and A. petrubanarescui as the most similar (about 99%) and A. idigensisas the most different (about 85%) species with others. The results of molecular analysis differentiated the six studied speices. The phylogenetic analysis using Maximum Likelihood (ML) and Maximum Parsimony (MP) showed A. idignensisas a separate taxon and A. eichwaldii and A. petrubanarescui as sister groups. The cytochrome b gene sequences revealed a high level of genetic differentiation within and among the six species, and demonstrated the suitability of partial cytochrome b gene (409 bp) sequence in determining their genetic diversity. In general, due to some factors such as the small size, low mobility and distribution, isolation or limited population and small size of habitats of this fish, it is possible that the species was evolved locally which could lead to some differences in the morphometric characteristics of the different species.

Keywords: taxonomy, morphometric and meristiccharacters, mitochondrial cytochrome b gene