Parallel Pattern Polymorphism in the Genus Phrynobatrachus (Amphibia: Ranidae)

Abstract

Savanna species of Phrynobatrachus exhibit a system of parallel polymorphism; morphs include uniform, vertebral stripe and dorsoconcolor patterns. Of three species occurring in Malawi, Phrynobatrachus natalensis, a pan-African anuran, exhibits the greatest stability of pattern. P. acridoides, of eastern African lowlands, has higher frequencies of nonuniform morphs and shows greater regional differences. P. ukingensis, the smallest of these three species, has an elevational range of 2,450 m, and shows significant differences in morph frequencies between most localities. In P. ukingensis, frequencies of striped morphs on the Nyika Plateau did not differ significantly over a 16-year period. Similarity of morph frequencies between syntopic species indicates influence of common environmental factors on selection for striped morphs. Greater nocturnalism in P. natalensis may explain the greater pattern stability in that species. Savanna species look alike and have similar pattern morphs. Rain forest species look very different from savanna species and have a different set of parallel morphs. Patterns in Phrynobatrachus probably function as protective camouflage against predators with keen vision.