Karyology of the Savi pine vole, Microtus savii (De Sélys-Longchamps, 1838) (Rodentia, Arvicolidae): G-, C-, DA/DAPI-, and AluI-bands.

Specimens of the Savi pine vole (Microtus savii) were collected from three localities in central (Pisa and Viterbo) and southern Italy (Rosarno, Calabria) and were karyotyped using G-, C-, DA/DAPI-, and AluI-banding. All karyotypes had 2n = 54 chromosomes and seemingly identical autosomal banding. The sex chromosomes of the southern Italian specimens, M. savii brachycercus, showed additional large blocks of heterochromatin. In the northern specimens, M. savii savii, the X chromosome is metacentric, whereas in the southern specimens of M. savii brachycercus the X chromosome is a much larger submetacentric chromosome, and the Y chromosome is more than twice the size of the Y in the northern specimens. DA/DAPI staining reveals three levels of fluorescent intensity in the sex chromosomes of the Calabrian specimens. The sex chromosomes of M. savii brachycercus also have the only AluI bands seen in either chromosome set. These data suggest a heterogeneous origin and composition of the C-band regions of these chromosomes. Preliminary data suggest that fertility is reduced in crosses between the two karyomorphs.