The common lowland toad Bufo valliceps has a large distribution in the southern United States, Mexico, and most of Central America; this ample distribution across diverse temperate and tropical habitats is unusual among frogs. Geographic variation in size, shape, skin texture, and color pattern among populations of this species was reviewed. Although there are great differences between extreme northern and southern populations, I did not find smooth clinal variation for any character examined. Nor is there a discrete break among these continuous morphological variables that separate the the northern and southern morphs. Variation in Biifo valliceps is characterized by a high degree of inter- and intrapopulational variation that cannot be attributed to simple trends associated with latitude, elevation, or climate. An analysis the relationship between body size and aridity, along a precipiation gradient on the Yucatan Peninsula, found no consistent covariation. Previous claims for a positive relationship between elevation and degree of development of the cranial crests were found not to be accurate. Although the several relatively distinct populations are referable to the taxa Bufo nebulifer and Bnfo valliceps wilsoni, 1 do not propose recognition of these taxa, pending further research.
Mendelson, J. R. (1998). Geographic variation in Bufo valliceps (Anura: Bufonidae), a widespread toad in the United States and Middle America / by Joseph R. Mendelson III. Scientific Papers, (8), 1-12. doi:10.5962/bhl.title.16231