 In spite of this, all extant unisexual species of "Ambystoma" share no nuclear DNA with "Ambystoma barbouri".Polyploidy, a numerical change in the number of chromosomes, is common in parthenogenic amphibians.Triploidy (having three sets of chromosomes), tetraploidy (four sets of chromosomes) and pentaploidy (five sets of chromosomes) are common in salamanders.