"Why Polyploidy is Rarer in Animals Than in Plants" Revisited

No satisfactory explanation of the rarity of polyploidy among animals exists. In taxa possessing a degenerate Y chromosome, polyploid speciation invariably disrupts the balance of X to autosomal gene product normally maintained by dosage compensation. This dosage balance is upset whether or not sex determination is disrupted. This factor may explain the distribution of polyploidy across taxa. In particular, plants may commonly show polyploidy because degenerate sex chromosomes are rare (first, because dioecy is rare, and second, because extreme Y degeneracy is rare among dioecious plants). Animals may rarely show polyploidy because degenerate sex chromosomes are common. Several predictions are discussed.