The predictability of evolution is debatable, with recent evidence suggesting that outcomes may be constrained by gene interaction networks . Whole-genome duplication (WGD; polyploidization-ubiquitous in plant evolution ) provides the opportunity to evaluate the predictability of genome reduction, a pervasive feature of evolution [3, 4]. Repeated patterns of genome reduction appear to have occurred via duplicated gene (homeolog) loss in divergent species following ancient WGD [5-9], with evidence for preferential retention of duplicates in certain gene classes [8-10]. The speed at which these patterns arise is unknown. We examined presence/absence of 70 homeologous loci in 59 Tragopogon miscellus plants from five natural populations of independent origin; this allotetraploid arose ~80 years ago via hybridization between diploid parents and WGD . Genes were repeatedly retained or lost in clusters, and the gene ontology categories of the missing genes correspond to those lost after ancient WGD in the same family (Asteraceae; sunflower family)  and with gene dosage sensitivity . These results provide evidence that the outcomes of WGD are predictable, even in 40 generations, perhaps due to the connectivity of gene products [8, 10, 12]. The high frequency of single-allele losses detected and low frequency of changes fixed within populations provide evidence for ongoing evolution.
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