Abstract
Testing Hardy-Weinberg equilibrium (HWE) is a fundamental approach for inferring population diversity and evolution, but its application to octoploids containing eight chromosome sets has not well been justified. We derive a mathematical model to trace how genotype frequencies transmit from parental to offspring generations in the natural populations of autooctoploids. We find that octoploids, including autooctolpoids undergoing double reduction, attach asymptotic HWE (aHWE) after 15 generations of random mating, in a contrast to diploids where one generation can assure exact equilibrium and, also, different from tetraploids that use 5 generations to reach aHWE. We develop a statistical procedure for testing aHWE in octoploids and apply it to analyze a real data set from octoploid switchgrass distributed in two ecologically different regions, demonstrating the usefulness of the test procedure. Our model provides a tool for studying the population genetic diversity of octoploids, inferring their evolutionary history, and identifying the ecological relationship of octoploid-genome structure with environmental adaptation.
Highlights
As an evolutionary force of the organism to buffer against environmental perturbations, the evolutionary mechanisms of polyploidy have been a long-standing subject of population and evolutionary genetic research (Bever and Felber 1992; Ramsey and Schemske 1998; Otto and Whitton 2000; Soltis et al, 2004; Fawcett et al, 2009)
Under a range of double reduction rates, we find that octoploids are always close to stabilize their genotype frequencies in 15 generations, suggesting that double reduction is neutral for asymptotic HWE (aHWE) (Figure 1A)
It has been recognized that polyploids gradually reach Hardy-Weinberg equilibrium (HWE) through random mating, but it is not very clear how many generations they mate to approach equilibrium (Geiringer 1949; Bever and Felber 1992)
Summary
Jing Wang 1, Xuemin Lv 1, Li Feng 1, Ang Dong 1, Dan Liang 1* and Rongling Wu 2*. Reviewed by: Diego Ortega-Del Vecchyo, National Autonomous University of Mexico, Mexico Pankaj Bhardwaj, Central University of Punjab, India. Testing Hardy-Weinberg equilibrium (HWE) is a fundamental approach for inferring population diversity and evolution, but its application to octoploids containing eight chromosome sets has not well been justified. We find that octoploids, including autooctolpoids undergoing double reduction, attach asymptotic HWE (aHWE) after 15 generations of random mating, in a contrast to diploids where one generation can assure exact equilibrium and, different from tetraploids that use 5 generations to reach aHWE. We develop a statistical procedure for testing aHWE in octoploids and apply it to analyze a real data set from octoploid switchgrass distributed in two ecologically different regions, demonstrating the usefulness of the test procedure. Our model provides a tool for studying the population genetic diversity of octoploids, inferring their evolutionary history, and identifying the ecological relationship of octoploid-genome structure with environmental adaptation
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