Rarely successful polyploids and their legacy in plant genomes

Polyploidy, or whole genome duplication, is recognized as an important feature of eukaryotic genome evolution. Among eukaryotes, polyploidy has probably had the largest evolutionary impact on vascular plants where many contemporary species are of recent polyploid origin. Genomic analyses have uncovered evidence of at least one round of polyploidy in the ancestry of most plants, fueling speculation that genome duplications lead to increases in net diversity. In spite of the frequency of ancient polyploidy, recent analyses have found that recently formed polyploid species have higher extinction rates than their diploid relatives. These results suggest that despite leaving a substantial legacy in plant genomes, only rare polyploids survive over the long term and most are evolutionary dead-ends.

► Polyploids have lower speciation and higher extinction rates than diploids.
► Rapid polyploid speciation expected by reciprocal gene loss models is questioned.
► Gene duplication rates probably exceed single nucleotide mutation rates owing to paleopolyploidy.
► Dosage-balance may not explain paralog retention patterns for all plant genomes.