Chromosomal mechanisms underlying the karyotype evolution of the oriental voles (Muridae, Eothenomys)

We have investigated the karyotype relationships of two oriental voles, i.e. the Yulong vole (Eothenomys proditor, 2n = 32) and the large oriental vole (Eothenomys miletus, 2n = 56) as well as the Clarke's vole (Microtus clarkei, 2n = 52), by a combined approach of cross-species chromosome painting and high-resolution G-banding comparison. Chromosome-specific painting probes were generated from flow-sorted chromosomes of E. proditor and hybridized onto metaphases of E. proditor, E. miletus and M. clarkei, leading to the establishment of genome-wide comparative chromosome maps. Our results demonstrate that Robertsonian translocations (centric fusions) have played a major role in the karyotype evolution of oriental voles with no obvious evidence for the involvement of tandem fusions as proposed previously and that the genome organizations of vole species are highly conserved. The comparative chromosome maps of these three vole species belonging to two phylogenetically distinct genera provide a framework for future studies on the karyotype evolution in voles.