The karyotes of some Australian Rodents (Rodentia : Muridae)

The number and morphology of the chromosomes of 11 species of Australian rodents have been described. It is suggested that Rattus lutreolus (2n = 42) is derived from an ancestor closely related to R. norvegicus (2n = 42) and that the former gave rise, in Australia, to R. fuscipes (2n = 38). R. fuscipes then gave rise to R. greyi (2n = 38) and R. assimilis (2n = 38) with both of which it is conspecific. Pseudomys minnie (2n = 48) and two species of Leggadina (2n = 48) have very similar karyotypes which differ from the karyotypes of two species of Notomys (2n = 48). The latter have apparently identical chromosomes. Within the Pseudomys group, marked changes in the heteromorphic pair of chromosomes have been involved in the evolution of karyotypes.