Biochemical and Morphological Variation of Leopard Frogs in Arizona

Evaluation of electrophoretic and morphological traits reveals three distinct members of the Rana ipipens complex present in Arizona. Examination of 653 frogs from 34 sites indicates that these three 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 three backcrosses have been 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 the morphological and electrophoretic findings support the recent work of my own and numerous others suggesting that the Rana ipipens complex consists of several species.