Hybridization between tetraploid and diploid species of treefrogs (Genus hyla).

An indirect analysis of female meiotic mechanisms in the tetraploid (4n = 48) grey treefrog, Hyla versicolor, was performed by examining artificially produced hybrids. First generation hybrids between a H. versicolor female from Canada (4n = 48) and a H. arborea male from France (2n = 24) were all triploid and appeared to contain two sets of chromosomes from H. versicolor and one set from H. arborea. Males and females were produced in equal numbers but testes in general were more completely developed than ovaries. Electrophoretic analysis of selected allozyme loci suggested that gene products from the two parents were not equally expressed. Backcross hybrids were triploid, tetraploid, and pentaploid but did not appear to contain recognizable chromosomes from the H. arborea grandparent. Allozymes from these hybrids indicated that only H. versicolor alleles were expressed, as none of the distinctive H. arborea alleles present in the triploid male parent were present in the offspring. It was concluded that preferential pairing of chromosomes and gene regulatory biases may help to explain factors that relate to the ability of tetraploids to hybridize with even distantly related taxa and may be involved in the rediploidization process that usually follows polyploidization.