A natural hybrid between Hyla arborea and Hyla meridionalis detected by mating calls

A tree-frog with unusual mating calls was found in an area of sympatry between H. arborea and H. meridionalis. This individual was studied by analysis of mating call structure and allozyme variation. The structure of the testes was also examined. The intermediate characteristics of the mating calls, the heterozygosity of all discriminative loci examined, and the apparent sterility, as shown by testis histology, all corroborate the identification of this hybrid.