Polyploidy is whole genome duplication, a genetic phenomenon which is widespread in plants and uncommon in animals. The ancestry of most if not all plants includes a doubling of all the chromosomes. In addition, many plant species were formed by crossing between two existing species, with subsequent doubling of the genome which made the hybrid fertile. (See previous blogs Intro to Polyploidy, Crop Plant Polyploidy, Speciation via Polyploidy).
Long known and still poorly understood is variation in polyploidy within a species.
fireweed (Chamerion) has within-species polyploidy |