<P> Mixoploidy is quite commonly observed in human preimplantation embryos and includes haploid / diploid as well as diploid / tetraploid mixed cell populations . It is unknown whether these embryos fail to implant and are therefore rarely detected in ongoing pregnancies or if there is simply a selective process favoring the diploid cells . </P> <P> Polyploidy is pervasive in plants and some estimates suggest that 30--80% of living plant species are polyploid, and many lineages show evidence of ancient polyploidy (paleopolyploidy) in their genomes . Huge explosions in angiosperm species diversity appear to have coincided with the timing of ancient genome duplications shared by many species . It has been established that 15% of angiosperm and 31% of fern speciation events are accompanied by ploidy increase . </P> <P> Polyploid plants can arise spontaneously in nature by several mechanisms, including meiotic or mitotic failures, and fusion of unreduced (2n) gametes . Both autopolyploids (e.g. potato) and allopolyploids (e.g. canola, wheat, cotton) can be found among both wild and domesticated plant species . </P> <P> Most polyploids display novel variation or morphologies relative to their parental species, that may contribute to the processes of speciation and eco-niche exploitation . The mechanisms leading to novel variation in newly formed allopolyploids may include gene dosage effects (resulting from more numerous copies of genome content), the reunion of divergent gene regulatory hierarchies, chromosomal rearrangements, and epigenetic remodeling, all of which affect gene content and / or expression levels . Many of these rapid changes may contribute to reproductive isolation and speciation . However seed generated from interploidy crosses, such as between polyploids and their parent species, usually suffer from aberrant endosperm development which impairs their viability, thus contributing to polyploid speciation . </P>

An example of polyploidy is found in a plant having
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