Molecular events during chromosomal divergence of the South American rodent Graomys griseoflavus

Graomys griseoflavus (Waterhouse, 1837) is a South American phyllotine rodent having an autosomal polymorphism produced by a sequence of llobertsonian fusions. The chromosomal divergence was correlated with the molecular organization of two satellite DNA families (EG250 and Hpa3.2) and the second internal transcribed spacer (ITS11) of ribosomal DNA, These studies were performed by Southern hybridization on all G. griseoflavus karyomorphs and other closely related cricetids. When Graomys karyomorphs were compared, interkaryomorphic differences were found at the methyl- ation pattern level of EG250 satellite and the molecular organization of Hpa3.2 satellite and ITSII. The findings support the hypothesis that Graomys griseoflavus karyomorphs are evolving separately, probably driving a chromosomal speciation process between 2 n = 42-41 and 2n = 38-34 individuals.