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.
Polyploidy has long been considered a major force in plant evolution. Ledyard Stebbins, Jr., an architect of the Modern Synthesis, elegantly addressed a broad range of topics, from genes to chromosomes to deep phylogeny, but some of his most lasting insights came in the study of polyploidy.
Here, we review the immense impact of his work on polyploidy over more than 60 years, from his entrance into this fledgling field in the 1920s until the end of his career.
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.Stebbins and his contemporaries developed a model of polyploid evolution that persisted for nearly half a century.As new perspectives emerged in the 1980s and new genetic tools for addressing key aspects of polyploidy have become available, a new paradigm of polyploidy has replaced much of the Stebbinsian framework.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.