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.

Item Type:	Refereed Article
Research Division:	Biological Sciences
Research Group:	Evolutionary biology
Research Field:	Animal systematics and taxonomy
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in the environmental sciences
UTAS Author:	Stewart, NJ (Dr Niall Stewart)
UTAS Author:	Munday, BL (Dr Barry Munday)
ID Code:	22589
Year Published:	2001
Web of Science® Times Cited:	74
Deposited By:	Health Sciences A
Deposited On:	2001-08-01
Last Modified:	2011-11-18
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