 The divergence of the two diploid progenitors occurred approximately 5.5 to 6.3 million years ago, and they hybridized to form p-annua around 50,000 years ago. The diploid genomes are similar in terms of chromosome structure, but differ significantly due to the divergent evolutionary history of their transposable elements. This results in a 1.7x difference in genome size. Additionally, the allotetropoid p-annua has experienced biased movement of retro-transposans from the A-subgenome to the B-subgenome. Furthermore, the B-subgenome is preferentially accumulating genes and is more highly expressed than the A-subgenome. Whole genome resequencing of several additional p-annua accessions revealed large-scale chromosomal rearrangements characterized by extensive TE downsizing and evidence to support the genome-balance hypothesis. These findings suggest that the divergent evolution of the diploid progenitors was key in conferring upon p-annua its remarkable phenotypic plasticity. Additionally, plant genes and transposable. This article was authored by Christopher W. Benson, Matthew R. Shelterer, Peter J. Morne, and others.