Iranian plateau is located in the southern margin of genus Allactaga distribiution and so far 5 species have been identified for Iran. Most of the eastern half of the Iranian plateau includes deserts and open plains which is a good habitat for dipodoids. Adaptation on desert habitats and dry and semi-arid ecosystem had caused a great deal of convergence between the various species of the genus Allactaga. On the other hand, chromosomal characteristics for this group of rodents were significantly fixed and so far, inter-species variation has not been reported to them. Recent studies, based on molecular data, have shown considerable variation for the genus Allactaga throughout its distribution region in palaearctic and especially in Iran. In this way, the presence of cryptic species is frequent for this group of rodents has been reported. Hence dipodoids are a very ideal model for the study of speciation and biodiversity. The first objective of this study was to investigate the molecular diversity of the genus Allactaga in northeastern Iran. And in the next stage, the presence of Allactaga williamsi Thomas, 1897 in the north east of Iran is being investigated. For this purpose, in the summer of 2017, 8 specimens were collected in the Kopet-Dagh Mountains using nets. Comparisons based on morphological characteristics, skull and teeth, morphometric characteristics, cytogenetic studies, and also molecular study using mitochondrial gene data (cytochrome b). Chromosomal study by c-banding method did not show difference between Kopet-Dagh population and other species present in this region (2N=48, FNa=92). However Compared with A. elater, A. toussi and A. hotsoni showed a significant Morphological differences. And cmpared with A. williamsi, there are significant difference in some of the characters. The molecular analysis based on the cytb gene indicates a significant divergence between the Kopet-Dagh population and other Allactaga species. The genetic variation of the Kopet-Dagh population with A. williamsi is about 15%, which is certainly more than inter-species differences. Thus the result of morphometric and molecular analyzes, deny the presence of A. williamsi in north east of Iran. The high genetic variation between the specimens studied compared with A. williamsi indicates a distinct species that is likely to be a new species in the genus Allactaga.

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