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

Abstract

Sympatric populations of the leaf-frogs Phyllomedusa distincta (2n = 26) 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 may not function adequately as a premating isolation mechanism. Triploids apparently exhibit low fertility or sterility, supporting the assertion that diploid and tetraploid populations are valid species. We suggest that P. tetraploidea originated by autopolyploidy of P. distincta, based on the following evidence: (1) the indistinguishable vocalizations of diploid and tetraploid species, and (2) the geographic distribution of species in the Phyllomedusa burmeisteri group.