Skin Tags and Ventral Melanism in the Rio Grande Leopard Frog

Abstract

Leopard frogs from the lower Rio Grande valley of Texas and Mexico normally have mottled throats and pectoral areas which distinguish them from other species of leopard frogs in the United States. Varying melanism of the undersurfaces is due in part to pigment con- centration and dispersion in melanophores under environmental changes. We conclude that these features among others characterize Rana berlandieri Baird and that the species is primarily a Mex- ican member of the pipiens complex. About 1 percent of the Rio Grande population is afflicted with papilla-like structures, termed skin tags, as the result of wounding. A yellow-legged population, believed to be of the same species, occurs in the state of Sina- loa of western Mexico, for which the name forreri Boulenger is available. It is concluded that Rana berlandieri is a Mexican species with several subspecies encircling the central plateau (ex- cept to the north) and entering the United States on its southern borders. This postulates two separate groups of leopard frogs, those in the United States being referred to as Rana pipiens with its subspecies and those of Mexico as Rana berlandieri with its subspecies. * * *