Comparative cytogenetics of hamsters of the genus <i>Calomyscus</i>

Karyotypes of <i>Calomyscus</i> from different regions of Turkmenistan, Iran, and Azerbaijan were studied using chromosome banding (G- and C-banding) and analyses of meiosis in laboratory hybrids. Extensive variation in the diploid number and the number of autosomal arms (FNa) was revealed (2n = 30, FNa = 44; 2n = 32, FNa = 42; 2n = 44, FNa = 46; 2n = 44, FNa = 58; 2n = 37, FNa = 44; 2n = 50, FNa = 50; 2n = 52, FNa = 56). Centric and tandem fusions and heterochromatin changes were identified as the major modes of karyotype evolution in this group. Natural hybrids between individuals with different karyotypes were recorded, and regular chromosome pairing in meiosis was observed in laboratory hybrids. Fluorescence in situ hybridization with a 353-bp <i>Bsp</i>RI complex tandem repeat indicated that chromosomal repatterning occurred recently within the genus. There is no unequivocal evidence suggesting the role of chromosomal change in the speciation of the populations of <i>Calomyscus</i> examined.