Gene duplication at an isocitrate dehydrogenase locus in Scaphiopus

Spadefoot toads of the subgenus Scaphiopus have two isocitrate dehydrogenase loci, with no intergenic interaction between them. Toads of the subgenus Spea have three Idh loci, with intergenic enzymes formed between two of them, providing strong evidence for their homology and the origin of one through a duplication process. The Idh phenotype of interspecific hybrids is consistent with the theory of a gene duplication.