A study, of the distribution and relationships of R. aurora, R. cascadae and R. pretiosa in Oregon is undertaken. A majority of the specimens examined were collected from an area in west-central Oregon with dimensions of approximately one hundred and forty miles by eighty miles. The taxonomic status of the frogs has been briefly summarized. R. pretiosa is distinguished from the other two forms by the shorter legs, greater amount of webbing, lack of mottling on the sides, lack of a mask and the greater roughness of the skin. R. aurora is distinguished from R cascadae by the red ventral color of R. aurora as opposed to the yellowish venter of R. cascadae, by the red, and yellow heavily mottled groin of R. aurora compared with the yellowish lightly mottled groin of R. cascadae, by the greater roughness of the skin in R. cascadae. Three species are recognized, Rana aurora, R. cascadae and R. pretiosa, the latter with two subspecies of R. p. pretiosa and R. p. luteiventris. R. aurora and R. pretiosa are the most distinct of the forms while R. cascadae most closely resembles R. aurora in its external morphology, but in some characters is intermediate between R. aurora and R. pretiosa. The distribution of the frogs in Oregon may be summarized as follows: R. aurora occurs in western Oregon east into the lower foothills of the western slope of the Cascades. R. pretiosa occurs all over the state, except the higher parts of the northern Oregon Cascades, in two subspecies, R. p. pretiosa west of the Cascades and R. p. luteiventris irt eastern Oregon. R. cascadae is found in a narrow strip down the Cascades at least as far south as Crater Lake.
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文章 : 英语