Phylogenetic Analysis of 18S rRNA and the Mitochondrial Genomes of the Wombat, <Emphasis Type="BoldItalic">Vombatus ursinus,</Emphasis> and the Spiny Anteater, <Emphasis Type="BoldItalic">Tachyglossus aculeatus:</Emphasis> Increased Support for the Marsupionta Hypothesis |
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Authors: | Axel Janke Ola Magnell Georg Wieczorek Michael Westerman Ulfur Arnason |
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Institution: | 1.Department of Genetics, Division of Evolutionary Molecular Systematics, University of Lund, S?lvegatan 29, S-223 62 Lund, Sweden,SE;2.Department of Genetics, La Trobe University, Bundoora, Victoria 3083, Australia,AU |
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Abstract: | The monotremes, the duck-billed platypus and the echidnas, are characterized by a number of unique morphological characteristics,
which have led to the common belief that they represent the living survivors of an ancestral stock of mammals. Analysis of
new data from the complete mitochondrial (mt) genomes of a second monotreme, the spiny anteater, and another marsupial, the
wombat, yielded clear support for the Marsupionta hypothesis. According to this hypothesis marsupials are more closely related
to monotremes than to eutherians, consistent with a basal split between eutherians and marsupials/monotremes among extant
mammals. This finding was also supported by analysis of new sequences from a nuclear gene—18S rRNA. The mt genome of the wombat
shares some unique features with previously described marsupial mtDNAs (tRNA rearrangement, a missing tRNALys, and evidence for RNA editing of the tRNAAsp). Molecular estimates of genetic divergence suggest that the divergence between the platypus and the spiny anteater took
place ≈34 million years before present (MYBP), and that between South American and Australian marsupials ≈72 MYBP.
Received: 28 October 2000 / Accepted: 23 March 2001 |
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Keywords: | : Phylogenetics — Marsupionta — Theria — Spiny anteater — Wombat — Mitochondrial DNA — 18S rDNA |
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