This page has been archived and is no longer updated. Polyploidy is the heritable condition of possessing more than two complete sets of chromosomes. Polyploids are common among plants, as well as among certain groups of fish and amphibians. For instance, some salamanders, frogs, and leeches are polyploids.
Many of these polyploid organisms are fit and well-adapted to their environments. These species that have experienced ancient genome duplications and then genome reduction are referred to as paleopolyploids. This article discusses the mechanisms underlying polyploidy, and both the advantages and disadvantages of having multiple sets of chromosomes. Researchers usually make a distinction between polyploids that arise within a species and those that arise due to the hybridization of two distinct species.
The former are known as autopolyploids, while the latter are referred to as allopolyploids. Autopolyploids are essentially homozygous at every locus in the genome. However, allopolyploids may have varying degrees of heterozygosity depending on the divergence of the parental genomes. Heterozygosity is apparent in the gametes that polyploids produce.
Allopolyploids can generally be distinguished from autopolyploids because they produce a more diverse set of gametes Figure 2. Different species exhibit different levels of tolerance for polyploidy. For example, polyploids form at relatively high frequency in flowering plants 1 per , individuals , suggesting that plants have a remarkably high tolerance for polyploidy.
This is also the case for some species of fish and frogs. Due to the high incidence of polyploidy in some taxa, such as plants, fish, and frogs, there clearly must be some advantages to being polyploid. A common example in plants is the observation of hybrid vigor, or heterosis , whereby the polyploid offspring of two diploid progenitors is more vigorous and healthy than either of the two diploid parents.
