The evolutionary importance of polyploidy
Barker, Michael , Scarpino, Samuel , Mayrose, Itay .
The Evolutionary Importance of Polyploidy.
Although whole genome duplicationpolyploidyis one of the most conspicuous genomic features of plants, there remains considerable debate surrounding the role of polyploidy in evolutionary process. This debate now centers on three main hypothess: 1) polyploids are drivers of diversification, 2) polyploids lead to evolutionary dead-ends, and 3) polyploid evolution is largely a neutral, ratchet-like process. If polyploids are more vigorous or more adaptively plastic than their diploid progenitors, then they may be more tolerant of major climatic change or more adaptable than diploids under those conditions, and thereby persist while the diploids go extinct. Fawcett et al. (2009) raised the possibility of polyploidy-biased lineage survivorship through the Cretaceous-Tertiary boundary, a period when about 60% of all plant species went extinct. These results, coupled with an observed positive correlation between the incidence of polyploidy and species richness (Otto and Whitten 200), lead to the hypothesis that polyploids are drivers of diversification. In contrast, several studies have now provided empirical estimates of speciation and extinction rates of polyploids and diploids, which have failed to find evidence for a polyploid evolutionary advantage: Wood et al. (2009) found no evidence for higher polyploid diversification rates, and Mayrose et al. (2011) found that rates were for newly formed polyploids, as compared to congeneric diploids. These studies have led some to conclude that most polyploids lead to evolutionary dead ends (Arrigo and Barker 2012). A third explanation, originally proposed by Stebbins (1971), is that polyploids should increase in frequency over time in a ratchet-like manner because ploidal increases are largely irreversible. Therefore, polyploidy incidence would increase even if polyploids had lower long-term fitness or lower diversification rates, as compared to their diploid relatives. Meyers and Levin (2006) and Scarpino et al. (2014) found evidence for this hypothesis, specifically finding that polyploid evolution is largely neutral, occurring in a ratchet-like process by fitting birth/death models to ploidal distribution data from 60 angiosperm genera.
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1 - University of Arizona, Department of Ecology & Evolutionary Biology
Presentation Type: Symposium Presentation
Location: Salon 4/The Shaw Conference Centre
Date: Wednesday, July 29th, 2015
Time: 1:30 PM
Candidate for Awards:None