Calomyscus elburzensis and C. hotsoni are two species of the rodents family Calomyscidae which are distributed mainly in Iran. Herein, we evaluated the habitat and ecological differences of these two brush-tailed mice in order to test the credibility of a hypothesis stating that species from habitats with different climates and vegetation show greater intraspecific differentiation than those from areas with more similar climates and vegetation. This study was carried out in four rocky regions in Iran between 2013 and 2015. Totally 52 brush-tailed mice were captured from Kopet-Dag, Khaje-Morad, Ark, and Shadan and Olang during the field studies. Maximum parsimony analysis inferred from mitochondrial DNA sequences (Cytb) was used for species identification, and also comparison of mean Kimura 2-paramater distances was performed. According to the molecular studies, specimens from the first two regions were assigned to C. elburzensis and samples from Ark, and Shadan and Olang belonged to C. hotsoni. The mean distances within all examined Iranian samples of both C. elburzensis and C. hotsoni were 2.3% and 0.9%, respectively. Based on our field studies, C. elburzensis were captured either from “cold mountainous” climate zone with Juniperus excelsa as main vegetation cover or from “Mediterranean” in which Pistacia atlantica is predominant vegetation. C. hotsoni were found in “hot dry desert” and “cold semi-desert” regions both characterized by Ephedra sp. and Avena sativa vegetation cover. Dog rose seeds were themain food of C. elburzensis in Kopet-Dag, whereas brush-tailed mice in the other three regions fed mainly on Mount Atlas pistache fruits. C. elburzensis inhabited concealed rock crevices, but C. hotsoni were found living in burrows which were digged in the soft soils. Individuals of C. hotsoni showed more calm behavior as compared with C. elburzensis. Meriones persicus and Cricetulus migratorius (Rodentia) as well as Ochotona rufescence (Lagomorpha) were the most abundant small mammals encountered with C. elburzensis,while M. persicus was the most successful rodent with sympatric colonies with C. hotsoni. In conclusion, in accordancewith the greater genetic distances observed in C. elburzensis populations as compared with C. hotsoni, more significant differences in the habitat structure were also found for the first species in different parts of its distribution range.

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