Has the Polyploid Wave Ebbed?

Abstract

There was a wave of whole genome duplications (WGD) during and subsequent to the K-Pg interface, which was followed by an increase in the proportion of species that were polyploid. I consider why this wave of polyploid speciation has continued to rise through the divergent evolution of polyploid lineages, and through rounds of homoploid and heteroploid chromosomal change. I also consider why the polyploid speciation wave is likely to rise in the next millennium. I propose that the speed of polyploid genesis through ploidal increase and through diversification among polyploids likely will be greater than the speed of diploid speciation. The increase in polyploid diversity is expected to lag well behind episodes of WGD, owing to the very long period required for species diversification either by lineage splitting or additional rounds of polyploidy, in addition to the long period of genomic adjustment to higher ploidal levels in neopolyploids.

The evolutionary conundrum of whole‐genome duplication

“…Assuming a potential advantage of WGD under disturbed environments, it is tempting to speculate on the future of current polyploids. For example, in the context of the ongoing sixth mass extinction with a rate of extinction up to 500 times greater (Humphreys et al, 2019) than the background rate of extinction, should we expect a relative increase in the occurrence of polyploids versus diploids in the major plant lineages (Levin, 2020)? Tackling this question, as well as understanding the molecular mechanisms ultimately responsible for an advantage of duplicated genomes over nonduplicated ones under stressful or disturbed environments, could come from evolutionary competition experiments of polyploid versus nonpolyploid populations of a suitable plant model organism.…”

The Origin of the Legumes is a Complex Paleopolyploid Phylogenomic Tangle Closely Associated with the Cretaceous–Paleogene (K–Pg) Mass Extinction Event

“…Polyploidy could have helped ancestral legumes and other plant lineages to both survive the mass extinction event and rapidly diversify owing to differential gene loss and other processes of diploidization ( Adams and Wendel 2005 ; Dodsworth et al 2016 ). On the other hand, many paleopolyploidy events significantly pre- and postdate the KPB and more extensive sampling of recently diversified groups may reveal a weaker pattern of KPB clustering, or a pattern of WGDs associated with episodes of rapid global change more generally ( Cai et al 2019 ; Levin 2020 ). Nevertheless, the timings of two WGDs as well as the initial diversification of the legumes close to the KPB ( Fig.…”

Intricate Distribution Patterns of Six Cytotypes of Allium oleraceum at a Continental Scale: Niche Expansion and Innovation Followed by Niche Contraction With Increasing Ploidy Level

“…Polyploidy is a widespread phenomenon among flowering plants (e.g., Wendel, 2000 ; Van de Peer et al, 2017 ). Several lines of evidence suggest that all flowering plants have experienced several polyploid events at some points in their ancestry (Wood et al, 2009 ; Jiao et al, 2011 ), and polyploidization is also an active evolutionary process in many lineages (Soltis and Soltis, 2012 ; Soltis et al, 2016 ; Levin, 2020 ). Before becoming evolutionarily successful, newly formed polyploids often have to overcome numerical inferiority, mating incompatibility, and competition with parents (Levin, 1975 ).…”