Desert hamsters (Phodopus roborovskii) are widely distributed in the deserts and semi-deserts of western and northern China,western and southern Mongolia,eastern Kazakhstan and Russia (Tuva) .As this species is associated with open sands,its distribution could be affected by alternations of arid and humid climatic phases over time.Analysis of the genetic structure of the species allows us to reconstruct its history during these changes.We analyzed sequences of the Cytochrome B (cyt b) gene of 108 exemplars from 36 sites across the species range (Kazakhstan,Tuva,Mongolia,China) .The modern area of the species forms a star-like structure centered in the Alashan desert with vertices directed to the West,North,North-West and East.The lack of correspondence between the phylogenetic relationships among haplotypes and their geographical distribution allowed us to assume that the contemporary genetic structure of this species in Western and Southern Mongolia formed as a result of several external waves of migration from the southern center of the origin,and is probably related to the star-like configuration of the Alashan desert.Genetic diversity in Ubsunur and Zaysan Hollows is different from the Alashan area and is suggestive of dispersal barriers in the past.We infer that this gap is associated with a relatively recent humid phase with widespread forest and meadow habitats,which were unsuitable for this species.In the future,if aridification occurs,the isolated parts of the range may reunite.