Karyotype relationships between four distantly related marsupials revealedby reciprocal chromosome painting

Marsupial karyotypes have shown extensive conservation even between distant ly related groups with a high diversity of life forms and reproductive biol ogy. Banding analysis has been the main test for assessing their homologies and chromosome rearrangements. More recently, cross-species reciprocal chr omosome painting has been developed and applied to several mammalian specie s and has shown homologies and rearrangements not revealed by banding analy sis. Karyotype relationships between four marsupial species, Sminthopsis cr assicaudata, Potorous tridactylus, Trichosurus vulpecula and Macropus eugen ii, which are from different families in two orders, were investigated and presented in the form of comparative chromosome maps. These show that only a limited number of chromosomal rearrangements have occurred during their e volution. A karyotype phylogeny of the four marsupials was derived from the se maps. A comparison between published gene location and the comparative c hromosome maps for these species is presented and inconsistencies with prev ious gene mapping data indicated.