The time of divergence of rats (genus Rattus) and mice (genus Mus) is
a bit controversial. The hybridization data presented by Catzeflis et al.
(1987) are interpreted as indicating a divergence time of 8.8(6.9-10.8)Mya,
based on the authors' calibration of their molecular clock using fossil-
record dates. Sarich's (1985) personal and fascinating discussion
expresses considerable skepticism of conventional interpretations of the
fossil record of Murid rodents, which are often based on a single tooth; he
regards the data (albumin distances together with DNA annealing data) as
being consistent with a divergence time of 22-24Mya. On top of this 2-3-
fold uncertainty, you can factor in your own feelings about possible
differences in evolutionary rates between rodents and other mammals (see
the discussion between Eastal and Wu & Li, ending with Walter Fitch's
comments in Mol. Biol. Evol. 4:81-82, 1987).
Catzeflis, F.M., Sheldon, F.H., Ahlquist, J.E. and Sibley, C.G.: DNA-DNA
hybridization evidence of the rapid rate of Muroid rodent DNA evolution.
Mol. Biol. Evol. 4:242-53, 1987
Sarich, V.M.: Rodent macromolecular systematics. In Luckett, W.P. and
Hartenberger, J.-L. (eds.): Evolutionary relationships among rodents, pp.
423-52, Plenum Press, New York, 1985
Cheers,
George
***************************************************************
* George A. Gutman *
* Department of Microbiology Tel:(714)856-6593 *
* and Molecular Genetics FAX:(714)856-8598 *
* University of California BITNET: GAGUTMAN at UCI *
* Irvine CA 92717 INTERNET: GAGUTMAN at UCI.EDU *
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