Biochemical and Morphological Variation of Leopard Frogs in Arizona

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Abstract
Evaluation of electrophoretic and morphological traits reveals 3 distinct members of the Rana pipiens complex present in Arizona [USA]. Examination of 653 frogs from 34 sites indicates that these 3 forms, designated Northern, Southern and Lowland, are largely allopatric and can be distinguished from each other morphologically. Where geographic replacement occurs, the transition is discontinuous with respect to protein phenotypes and associated morphology. The Southern type is sympatric at a number of locations with either the Lowland or the Northern form. Where sympatry occurs the morphotypes and their associated protein patterns remain essentially distinct except for occasional hybrids. Ten Northern-Southern F1 hybrids and 3 backcrosses are identified among 143 individuals from sympatric sites. Only F1 hybrids (3/43) were detected among the 96 individuals from Lowland-Southern collecting sites. F1 hybrids are rare and backcrosses even rarer. Both morphological and electrophoretic findings support the recent work suggesting that the R. pipiens complex consists of several species.