Hexaploidies can form in either one step (instant triplication of the genome) or two steps ( 1) tetraploidy, 2) a tetraploid gamete fuses with a diploid gamete creating a sterile triploid which then regains fertility by doubling its genome again, creating a hexaploid). Bread wheat is an excellent example of this process where most of the intermediate species still exist.
Einkorn wheat is a diploid containing only the A genome.
Identifying and characterizing plant paleopolyploidies is ongoing research.
They are identified through whole genome comparisons using a combination of the data derived from genomic structure (e.g. As such, detecting these events and determining which lineages share what subset are continually changing.
syntenic dotplots) and evolutionary distances (e.g. The images presented here represent our views right now, but are subject to change.
Events that were previously undetected or missed can suddenly be seen with an improved build of a genome or the sequencing of a fortuitously placed outgroup.
This webpage in maintained by James Schnable, a member the Co Ge development team.
As new genomes become available, and previous genomes are updated, I will continue to improve these figures.
If you know of a new whole genome duplication not listed here, a paper that should be credited but isn't, or interesting information about any specific whole genome duplication that you think should be included in the summaries please don't hesitate to contact me so I can get the information up here.
If you would like a citable reference for the data collected here and aren't comfortable citing a website directly, here's the citable version (complete with DOI): For a version of this tree with all common names replaced by scientific ones, see the bottom of this page.
Finally the AB wheat crossed with goatgrass, a wild diploid species which carries the D genome, creating the bread wheat grown today around the world which carries three genomes: A, B, and D.
The wheat hexaploidy is close to an ideal case with almost all the species involved still alive today.
For ancient hexaploidies it is hard to prove an event happened in 1-step or 2-steps, although we think based on patterns of gene loss that most ancient hexaploidies formed in two-step events.