Karyotype relationships between distantly related marsupials from South America and Australia

Reciprocal chromosome painting and G-banding were used to compare the karyo types of three Australian marsupials (Sminthopsis crassicaudata, Macropus e ugenii, Trichosurus vulpecula) and one South American marsupial (Monodelphi s domestica). The results revealed only a limited number of rearrangements between these species and that the four karyotypes can be described as diff erent combinations of fifteen conserved segments. Five chromosomes are tota lly conserved between M. domestica (pairs 1, 2, 5, 8 and the X) and the pre sumed 2n = 14 Australian ancestral karyotype, while M. domestica pairs 3 an d 6 and 4 and 7 would have been involved in fusion/fission rearrangements. Chromosome comparisons are presented in a chromosome homology map. Although the species studied diverged 70 million years ago, the karyotype of Monode lphis domestica is highly conserved in relation to those of Australian mars upials.