Chromosome polymorphism in Ctenomys minutus (Rodentia-Octodontidae)

a sample of 101 specimens of ctenomys minutus was collected along its geographic range. eight karyotypes (2n = 42, 45, 46a, 46b, 47, 48, 49 and 50) were found. the chromosome polymorphisms were due to robertsonian rearrangements and tandem fusions. the distribution of polymorphisms indicated three population blocks: northern (2n = 49 and 50), central (2n = 46a, 47, and 48) and southern (2n = 42, 45, and 46b). these findings suggest that this species is undergoing a speciation process due to geographic isolation.