SPECIATION BY POLYPLOIDY IN TREEFROGS - MULTIPLE ORIGINS OF THE TETRAPLOID, HYLA VERSICOLOR

Speciation by polyploidy is rare in animals, yet, in vertebrates, ther e is a disproportionate concentration of polyploid species in anuran a mphibians. Sequences from the cytochrome b gene of the mitochondrial D NA (mtDNA) were used to determine phylogenetic relationships among 37 populations of the diploid-tetraploid species pair of gray treefrogs, Hyla chrysoscelis and Hyla versicolor. The diploid species, H. chrysos celis, consists of an eastern and a western lineage that have 2.3% seq uence divergence between them. The tetraploid species, H. versicolor, had at least three separate, independent origins. Two of the tetraploi d lineages are more closely related to one or the other of the diploid lineages (0.18%-1.4% sequence divergence) than they are to each other (1.9%-3.4% sequence divergence). The maternal ancestor of the third t etraploid lineage is unknown. The phylogenetic relationships between t he two species and among lineages within each species support the hypo thesis of multiple origins of the tetraploid lineages.