Cytogenetic relationships in Rattus, Cremnomys, Millardia, Nesokia and Bandicota (Rodentia: Muridae)

Abstract

The karyology was studied in different taxa of Rattus, Cremnomys, Millardia, Nesokia and Bandicota. Chromosome banding patterns of 18 taxa belonging to 4 species of the genus Rattus, 2 species of Cremnomys, 1 species each of Millardia and Nesokia and 2 species of Bandicota are presented. Present studies and the karyological information of different taxa available from elsewhere have revealed that the karyotypes of Millardia, Cremnomys, Lenothrix (except L. canus) and Maxomys (M. bartelsii only) are unique and show little resemblance to Rattus, Stenomys, Berylmys and Leopoldamys. G-band comparison has revealed the presence of 4 pairs of similar autosomes in addition to conservation of the G-band pattern of the X chromosome in divergent karyotypes of Rattus rattus, Millardia meltada and Cremnomys cutchieus medius. Chromosome inversions, fusions and variations in constitutive heterochromatin have been identified. The presence of a few similar chromosomes suggests that these taxa have evolved from a common ancestral taxon. The conventional karyotype of Lenothrix canus and the Niviventer group of rats (Marshall, 1977) also reveal a pair of large subtelocentrics and a few pairs of small metacentrics similar to those observed in the subgenera Rattus, Stenomys, Berylmys and Leopoldamys. The autosomal complements of the lesser bandicoot-rats Nesokia indica and Bandicota bengalensis are alike and are related to those of species in the subgenus Rattus through only 2 pericentric inversions. A few pericentric inversions and a deletion may be assumed to compare the karyotype of the great bandicoot-rat B. indica indica with B. bengalensis. The other great bandicoot-rats, B. indica nemorivaga and B. indica savilei, have an additional pair of autosomes and the karyotype of the former subspecies has diversified through a few pericentric inversions also. © 1983 Dr W. Junk Publishers.