Phylogeny of Marsupials based on phosphoglycerate kinase DNA sequences
In this project DNA sequences were used to study the evolutionary relationships between the major groups of marsupials in Australasia and the Americas.
Major shifts in our understanding of the relationships of marsupials remain possible. For instance, in 1982 Szalay separated the group into two cohorts, the Ameridelphia, restricted to the Americas, and the Australidelphia, comprising all Australasian marsupials and, surprisingly, the South American "monito del monte" Dromiciops australis.
In this study (reported in Molecular Phylogeny and Evolution 11: 13-26) partial sequences were obtained for phosphoglycerate kinase (Download
) for 313 aligned bases of 41 individuals from 39 marsupial species. Four main monophyletic lineages are found in analyses of these data. These are the single genus orders Microbiotheria (Dromicopis australis) and Notoryctemorphia (Notoryctes typhlops - the Australian marsupial mole), a grouping of the American orders Didelphimorphia and Paucituberculata, and the Australasian species other than N. typhlops.
Within Australasia, there are again four main monophyletic groups; the Dasyuridae, two bandicoot lineages (one comprised of pseudogene sequences which clusters with the numbat, Myrmecobius fasciatus) and the Diprotodontia (kangaroo, Australian possums, etc). Two bandicoot sequences in the second lineage have inserts of about 1 kb with high levels of similarity to LINE 1 repeated sequence elements. The Diprotodontia has a low level of inter-sequence variation in comparison to the other Australian lineages, possibly explaining the failure to separate the members of the Phalangeridae and Petauridae, although this may also be due to the scoring of a pseudogene in one species.
The amount of sequence divergence within the Dasyuromorphia is substantial, presenting a striking contrast to the low variability of the Diprotodontia. This emphasises that efforts to conserve the evolutionary potential of the marsupials should fully consider the genetic diversity represented by the Dasyuromorphia, as well as their more conspicuous relatives.
Acknowledgements
Support for this project was provided by the Australian Museum, The Ian Potter Foundation and the Ken Myer Bequest to the Evolutionary Biology Unit.
Participant
Don Colgan
Selected references
- Archer, M. (1984). The Australian marsupial radiation. In "Vertebrate Zoogeography and Evolution in Australasia" (M. Archer and G. Clayton, Eds.), pp. 635-808 . Hesperian Press, Perth.
- Kirsch, J.A.W., Dickerman, A.W., Reig, O.A., and Springer, M.S. (1991). DNA hybridisation evidence for the Australian affinity of the American marsupial Dromiciops australis. Proc. Natl. Acad. Sci. USA. 88:10465-10469.
- Krajewski, C., Buckley, M., and Westerman, M. (1997). DNA phylogeny of the marsupial wolf resolved. Proc. R. Soc. Lond. B, in press.
- Springer, M., Westerman, M., and Kirsch, J.A.W. (1994). Relationships among orders and families of marsupials based on 12S ribosomal DNA sequences and the timing of the marsupial radiation. J. Mammal. Evol. 2:85-115.
- Szalay, F.S. (1982). A new appraisal of marsupial phylogeny and classification. In "Carnivorous Marsupials" (M. Archer, Ed.), Vol. 2, 621-640. Royal Zoological Society of New South Wales, Sydney.
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