NATURAL HYBRIDIZATION BETWEEN DIPLOID AND TETRAPLOID SPECIES OF LEAF-FROGS, GENUS PHYLLOMEDUSA (AMPHIBIA)

Sympatric populations of the leaf-frogs Phyllomedusa distincta (2n = 2 6) and P. tetraploidea (4n = 52) were studied in southeastern Brazil. In a region of sympatry, seven of 15 leaf-frogs were triploid hybrids (3n = 39). The advertisement calls of both species are similar, and ma y not function adequately as a premating isolation mechanism. Triploid s apparently exhibit low fertility or sterility, supporting the assert ion that diploid and tetraploid populations are valid species. We sugg est that P. tetraploidea originated by autopolyploidy of P. distincta, based on the following evidence: (1) the indistinguishable vocalizati ons of diploid and tetraploid species, and (2) the geographic distribu tion of species in the Phyllomedusa burmeisteri group.