Revisiting the origin of octoploid strawberry

The cultivated strawberry (Fragaria ×ananassa) is an octoploid, and the identity of its four subgenomes has long been a mystery. In their recent strawberry genome publication, Edger et al. present a novel hypothesis: each subgenome originated from a different extant diploid progenitor, and the hexaploid species Fragaria moschata was a direct ancestor. We reanalyzed the four octoploid subgenomes in a phylogenomic context and our results support only two extant diploids progenitors; we also found no support for F. moschata as a direct ancestor. We identified assumptions in the Edger et al. tree-searching algorithm that prevent it from accepting extinct or unsampled progenitors, and we argue that this is a critical weakness of their approach.