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Mammalian Genome

, Volume 12, Issue 7, pp 513–517 | Cite as

Marsupials and Eutherians reunited: genetic evidence for the Theria hypothesis of mammalian evolution

  • J. Keith  Killian
  • Thomas R.  Buckley
  • Niall  Stewart
  • Barry L.  Munday
  • Randy L.  Jirtle

Abstract.

The three living monophyletic divisions of Class Mammalia are the Prototheria (monotremes), Metatheria (marsupials), and Eutheria (`placental' mammals). Determining the sister relationships among these three groups is the most fundamental question in mammalian evolution. Phylogenetic comparison of these mammals by either anatomy or mitochondrial DNA has resulted in two conflicting hypotheses, Theria and Marsupionta, and has fueled a ``genes versus morphology'' controversy. We have cloned and analyzed a large nuclear gene, the mannose 6-phosphate/insulin-like growth factor II receptor (M6P/IGF2R), from representatives of all three mammalian groups, including platypus, echidna, opossum, wallaby, hedgehog, mouse, rat, rabbit, cow, pig, bat, tree shrew, colugo, ringtail lemur, and human. Statistical analysis of this nuclear gene unambiguously supports the morphology-based Theria hypothesis that excludes monotremes from a clade of marsupials and eutherians. The M6P/IGF2R was also able to resolve the finer structure of the eutherian mammalian family tree. In particular, our analyses support sister group relationships between lagomorphs and rodents, and between the primates and Dermoptera. Statistical support for the grouping of the hedgehog with Feruungulata and Chiroptera was also strong.

Keywords

Growth Factor Fine Structure Mannose Nuclear Gene Statistical Support 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag New York Inc. 2001

Authors and Affiliations

  • J. Keith  Killian
    • 1
  • Thomas R.  Buckley
    • 2
  • Niall  Stewart
    • 3
  • Barry L.  Munday
    • 3
  • Randy L.  Jirtle
    • 1
  1. 1.Departments of Radiation Oncology and Pathology, Duke University Medical Center, Box 3433, Durham, North Carolina 27710, USAUS
  2. 2.Department of Biology, Duke University, Durham, North Carolina, 27708, USAUS
  3. 3.School of Biomedical Science, University of Tasmania, Launceston, Tasmania 7250, AustraliaAU

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