Immunological resolution of a diploid-tetraploid species complex of tree frogs.

Micro-complement fixation studies of eastern and western populations of the North American tree frog Hyla chrysoscelis reveal they have been genetically isolated for about 4 million years. Immunological comparisons of populations of the cryptic tetraploid Hyla versicolor indicate a recent origin, from hybridization between eastern and western H. chrysoscelis.