Geographic Variation and Taxonomic Revision of Rice Rats (Oryzomys palustris and O. argentatus) of the United States

• Published in: Journal of mammalogy 1989-08, Vol.70 (3), p.557-570
• Main Authors: Humphrey, Stephen R., Setzer, Henry W.
• Format: Article
• Language: English
• Subjects: Age; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Geographical variation; Keys; Mammalia; Mandible; Rats; Rice; Skull; Specimens; Taxa; Teeth; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution
• ISSN: 0022-2372; 1545-1542; 1545-1542; 0022-2372
• DOI: 10.2307/1381427

We evaluated geographic variation in O. argentatus and six named subspecies of O. palustris, using exploratory and confirmatory multivariate analyses of 12 skull measurements. We also conducted a preliminary analysis of pelage color, using colorimetry to describe spectral characteristics as continuous variables. Rice rats are highly variable in both cranial and pelage characters. Striking variation by age and sex corroborated the advice of Merriam (1901) that only adult males should be used for taxonomic investigation of Oryzomys. We found no species-level difference among these taxa, and we were unable to separate O. argentatus and most named subspecies of O. palustris from one another. Only two groups are distinguishable: O. p. palustris from the continental United States, and O. p. natator from peninsular Florida. The taxonomic arrangement of the genus Oryzomys in the United States appears to have been overly split on the basis of random variation in small samples.