Whole genome sequencing of 10 Capsella bursa-pastoris individuals

Over long periods polyploid genomes eventually lose genes and become diploid. However, how quickly this mechanism of gene loss occurs following polyploidization is unclear. By studying whole genome sequences of the recent tetraploid Capsella bursa-pastoris as well as its close relatives, we can gain insight into the early stages of gene loss in recent polyploids. We show first that C. bursa-pastoris originated through a hybridization event of two diploids. Second, we show that there is evidence of relaxed purifying selection in C. bursa-pastoris, but widespread gene loss has not yet occurred. This signal of relaxed purifying selection is driven by a combination of gene redundancy as well as demographic and historical factors that accompanied the hybridization event.