DNA content variability in several species of Australian and South American marsupials

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Abstract
The evaluation of DNA content in Australian marsupials (Martin & Hayman, 1967; Bick & Jackson, 1967) together with the morphological analysis of the karyotype (which shows a strong variability: 2n between 10 and 32 with modes at 14 and 22) has yielded useful information for the phylogenetic analysis of this order. In this paper the DNA content, evaluated microdensitometrically as Feulgen-DNA, is compared in 6 species of South American marsupials (Lutreolina crassicaudata Desmarest, Marmosa pusilla Desmarest, Marmosa agilis Burmeister, Didelphis marsupialis Linneus, Didelphis azarae. Temminck, Monodelphis dimidiata Wagner) and 5 species of Australian marsupials (Perameles gunnii Gray, Perameles nasuta Geoffroy, Macropus giganteus Zimmermann, Macropus robustus Gould and Potorous tridactylus Kerr). No data had so far been reported on the nuclear DNA content of the South American species. The mean values in the Australian and South American marsupials, are 124% and 120% respectively of those observed in man. The South American show a lower variability around the mean value in agreement with the well known predominance of the Robertsonian evolutionary mechanism in the karyotype of this group, while the Australian marsupials exhibit a higher variability, as expected from the more complex mechanism of their chromosome evolution.