The blind mole rats (Spalacinae) reveal fascinating chromosomal variation, resulting from complex karyotype re-arrangements. This variation occurs between species, between populations of single species (polytypy) and within populations (polymorphism). This article reviews the current knowledge on blind mole rats' karyotypes and their variation. A special attention is paid to differentiation of the karyotype within a species and the patterns of chromosomal variation, which result in evolution of distinct chromosomal races (cytotypes). The chromosome races are defined as a group of geographically contiguous or recently separated populations which share a similar chromosome complement by descent. The present review indicated the existence of 73 distinct chromosome races recorded in blind mole rats classified within the genus Nannospalax, along with the seven species recognized within the genus Spalax. In total, 12 distinct diploid numbers of chromosomes were reported (2n = 36-62); and variation in chromosome morphologies was observed between populations with the same number of chromosomes (NF = 62-124). The blind mole rats classified in the genus Spalax revealed rather uniform karyotype both between and within the recognized species. Considering the traditional species classified in the Nannospalax genus, 25 races can be distinguished within N. leucodon, 28 races within N. xanthodon and 20 races within N. ehrenbergi. Hybrids between the races are found only exceptionally and they seem to be almost absent in extensive areas (Europe, Turkey). This fact indicates that chromosomal evolution in blind mole rats may be related to speciation processes. The definitive phylogenetic and taxonomic conclusions can be derived only after application of reliable molecular markers and setting of estimates of genetic distances and gene flow between populations.
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Vol. 65 • No. 4