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Taxonomists have somewhat arbitrarily sectioned a clinal pattern of geographic variation of rice rats (Oryzomys longicaudatus) into three subspecies along the southwestern Andes. This treatment was reevaluated based on cranial, external, and penial morphometrics. Geographic and nongeographic variation was examined through univariate and multivariate statistics. Not three but only two groups are clearly evident. This pattern is interpreted as the result of vicariance caused by Pleistocene geomorphological and climatic changes. The size and kind of gap between the two groupings strongly suggest that two species and no subspecies of rice rats are recognized in Chile.
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Gallardo et al. (1990) studied this question.
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