Comparative chromosome painting between marsupial orders: Relationships with a 2n=14 ancestral marsupial karyotype

A 2n = 14 karyotype is shared by some species in each of the marsupial orde rs in Australian and American superfamilies, suggesting that the ancestral marsupial chromosome complement was 2n = 14. We have used chromosome painti ng between distantly related marsupial species to discover whether genome a rrangements in 2n = 14 species in two Australian orders support this hypoth esis. Cross-species chromosome painting was used to investigate chromosome rearrangements between a macropodid species Macropus eugenii (2n = 16) and a wombat species in a different suborder (Lasiorhinus latifrons, 2n = 14), and a dasyurid species in a different order (Sminthopsis macroura, 2n = 14) . We demonstrate that many chromosome regions are conserved between all thr ee species, and deduce how the similar 2n = 14 karyotypes of species in the two orders are related to a common ancestral 2n = 14 karyotype.