Abstract
The subterranean mole vole, Ellobius tancrei, with aspecific variability in autosomes (2n = 31–54) and unusual sex chromosomes (XX in males and females), represents an amazing model for studying the role of chromosome changes in speciation. New materials from the upper reaches of the Surkhob River in the Pamiro-Alay mountains resulted in the discovery of a new form with 2n = 30. The application of Zoo-FISH and G-banding methods allowed the detection of 13 pairs of autosomes as Robertsonian metacentrics originated after fusions of acrocentrics of an assumed ancestral karyotype of Ellobius tancrei with 2n = 54. The sex chromosomes (XX, in both sexes) and one pair of acrocentric autosomes are the only acrocentrics in this karyotype, and the set with 2n = 30 possesses the lowest possible chromosome number among populations of Ellobius tancrei.
Highlights
Occurring chromosome variability is essential for understanding the disputed role of chromosome changes in speciation (White 1978, King 1993)
Acrocentric chromosomes involved in the translocation were determined by G-banding as chromosomes number 24 and 26, according to the new nomenclature developed for E. tancrei, 2n = 54 (Bakloushinskaya et al 2012), and confirmed by applying Zoo-FISH probes MAG18 and MAG24 (Fig. 2)
The analysis of the spatio-temporal variation in the structure of a chromosomal polymorphism zone in E. tancrei with an interval of 25 years showed that the distribution of chromosomal forms within the area has not changed during this period, except for a small range expansion of a low-chromosomal form (2n = 32) at the western boundary (Lyapunova et al 2010)
Summary
Occurring chromosome variability is essential for understanding the disputed role of chromosome changes in speciation (White 1978, King 1993). Well-studied cases of extensive Robertsonian variation in species such as the house mouse, Mus musculus domesticus Schwarz et Schwarz, 1943 (Gropp et al 1969, Piálek et al 2005), the common shrew, Sorex araneus Linnaeus, 1758 (Ford et al 1957, Wójcik et al 2003), or the mole vole Ellobius tancrei (Lyapunova et al 1980, 2010) have their own specific features. All these species are widely distributed; for example, house mice are distributed all over the globe due to human activity. The last two factors may contribute to a rapid fixation of chromosome translocations due to more or less permanent monogamous bonds (our unpublished data)
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